<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_domain.sgml,v 1.20 2006/09/16 00:30:16 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_domain.sgml,v 1.21 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
These forms change whether a domain is marked to allow NULL
- values or to reject NULL values. You may only <literal>SET NOT NULL</>
+ values or to reject NULL values. You can only <literal>SET NOT NULL</>
when the columns using the domain contain no null values.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_index.sgml,v 1.11 2006/09/16 00:30:16 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_index.sgml,v 1.12 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
<xref linkend="SQL-CREATEINDEX" endterm="sql-createindex-title">
for details on the available parameters. Note that the index contents
will not be modified immediately by this command; depending on the
- parameter you may need to rebuild the index with
+ parameter you might need to rebuild the index with
<xref linkend="SQL-REINDEX" endterm="sql-reindex-title">
to get the desired effects.
</para>
<para>
This form resets one or more index-method-specific storage parameters to
their defaults. As with <literal>SET</>, a <literal>REINDEX</literal>
- may be needed to update the index entirely.
+ might be needed to update the index entirely.
</para>
</listitem>
</varlistentry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_opfamily.sgml,v 1.1 2007/01/23 05:07:17 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_opfamily.sgml,v 1.2 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
<para>
The <literal>OPERATOR</> and <literal>FUNCTION</>
- clauses may appear in any order.
+ clauses can appear in any order.
</para>
</refsect1>
type(s). The name of the operator or function occupying the slot is not
mentioned. Also, for <literal>DROP FUNCTION</> the type(s) to specify
are the input data type(s) the function is intended to support; for
- GIN and GiST indexes this may have nothing to do with the actual input
+ GIN and GiST indexes this might have nothing to do with the actual input
argument types of the function.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_sequence.sgml,v 1.15 2006/09/16 00:30:16 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_sequence.sgml,v 1.16 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
<term><literal>CYCLE</literal></term>
<listitem>
<para>
- The optional <literal>CYCLE</literal> key word may be used to enable
+ The optional <literal>CYCLE</literal> key word can be used to enable
the sequence to wrap around when the
<replaceable class="parameter">maxvalue</replaceable> or
<replaceable class="parameter">minvalue</replaceable> has been
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.92 2006/10/23 18:10:32 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.93 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
These forms set or remove the default value for a column.
The default values only apply to subsequent <command>INSERT</command>
commands; they do not cause rows already in the table to change.
- Defaults may also be created for views, in which case they are
+ Defaults can also be created for views, in which case they are
inserted into <command>INSERT</> statements on the view before
the view's <literal>ON INSERT</literal> rule is applied.
</para>
A disabled trigger is still known to the system, but is not executed
when its triggering event occurs. For a deferred trigger, the enable
status is checked when the event occurs, not when the trigger function
- is actually executed. One may disable or enable a single
+ is actually executed. One can disable or enable a single
trigger specified by name, or all triggers on the table, or only
user triggers (this option excludes triggers that are used to implement
foreign key constraints). Disabling or enabling constraint triggers
<xref linkend="SQL-CREATETABLE" endterm="sql-createtable-title">
for details on the available parameters. Note that the table contents
will not be modified immediately by this command; depending on the
- parameter you may need to rewrite the table to get the desired effects.
+ parameter you might need to rewrite the table to get the desired effects.
That can be done with <xref linkend="SQL-CLUSTER"
endterm="sql-cluster-title"> or one of the forms of <command>ALTER
TABLE</> that forces a table rewrite.
<listitem>
<para>
This form resets one or more storage parameters to their
- defaults. As with <literal>SET</>, a table rewrite may be
+ defaults. As with <literal>SET</>, a table rewrite might be
needed to update the table entirely.
</para>
</listitem>
<literal>CHECK</literal> constraints of the parent. Currently
<literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>, and
<literal>FOREIGN KEY</literal> constraints are not considered, but
- this may change in the future.
+ this might change in the future.
</para>
</listitem>
</varlistentry>
<para>
Adding a column with a non-null default or changing the type of an
existing column will require the entire table to be rewritten. This
- may take a significant amount of time for a large table; and it will
+ might take a significant amount of time for a large table; and it will
temporarily require double the disk space.
</para>
expression is not applied to the column's default value (if any); the
result might not be a constant expression as required for a default.
This means that when there is no implicit or assignment cast from old to
- new type, <literal>ALTER TYPE</> may fail to convert the default even
+ new type, <literal>ALTER TYPE</> might fail to convert the default even
though a <literal>USING</literal> clause is supplied. In such cases,
drop the default with <literal>DROP DEFAULT</>, perform the <literal>ALTER
TYPE</>, and then use <literal>SET DEFAULT</> to add a suitable new
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/analyze.sgml,v 1.20 2006/09/16 00:30:16 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/analyze.sgml,v 1.21 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
The statistics collected by <command>ANALYZE</command> usually
include a list of some of the most common values in each column and
a histogram showing the approximate data distribution in each
- column. One or both of these may be omitted if
+ column. One or both of these can be omitted if
<command>ANALYZE</command> deems them uninteresting (for example,
in a unique-key column, there are no common values) or if the
column data type does not support the appropriate operators. There
allows even very large tables to be analyzed in a small amount of
time. Note, however, that the statistics are only approximate, and
will change slightly each time <command>ANALYZE</command> is run,
- even if the actual table contents did not change. This may result
+ even if the actual table contents did not change. This might result
in small changes in the planner's estimated costs shown by
<command>EXPLAIN</command>. In rare situations, this
non-determinism will cause the query optimizer to choose a
<command>ANALYZE</command> and the amount of space occupied in
<literal>pg_statistic</literal>. In particular, setting the
statistics target to zero disables collection of statistics for
- that column. It may be useful to do that for columns that are
+ that column. It might be useful to do that for columns that are
never used as part of the <literal>WHERE</>, <literal>GROUP BY</>,
or <literal>ORDER BY</> clauses of queries, since the planner will
have no use for statistics on such columns.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/begin.sgml,v 1.34 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/begin.sgml,v 1.35 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
<para>
For reasons of backwards compatibility, the commas between successive
- <replaceable class="parameter">transaction_modes</replaceable> may be
+ <replaceable class="parameter">transaction_modes</replaceable> can be
omitted.
</para>
</refsect1>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/checkpoint.sgml,v 1.14 2006/09/16 00:30:17 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/checkpoint.sgml,v 1.15 2007/01/31 23:26:02 momjian Exp $ -->
<refentry id="sql-checkpoint">
<refmeta>
</para>
<para>
- Only superusers may call <command>CHECKPOINT</command>. The command is
+ Only superusers can call <command>CHECKPOINT</command>. The command is
not intended for use during normal operation.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.38 2006/11/04 19:03:51 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.39 2007/01/31 23:26:02 momjian Exp $
PostgreSQL documentation
-->
Because the planner records statistics about the ordering of
tables, it is advisable to run <xref linkend="sql-analyze"
endterm="sql-analyze-title"> on the newly clustered table.
- Otherwise, the planner may make poor choices of query plans.
+ Otherwise, the planner might make poor choices of query plans.
</para>
<para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/comment.sgml,v 1.34 2007/01/23 05:07:17 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/comment.sgml,v 1.35 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
The name of the object to be commented. Names of tables,
aggregates, domains, functions, indexes, operators, operator classes,
- operator families, sequences, types, and views may be schema-qualified.
+ operator families, sequences, types, and views can be schema-qualified.
</para>
</listitem>
</varlistentry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.77 2006/09/18 19:54:01 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.78 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
should not lead to problems in the event of a <command>COPY
TO</command>, but the target table will already have received
earlier rows in a <command>COPY FROM</command>. These rows will not
- be visible or accessible, but they still occupy disk space. This may
+ be visible or accessible, but they still occupy disk space. This might
amount to a considerable amount of wasted disk space if the failure
- happened well into a large copy operation. You may wish to invoke
+ happened well into a large copy operation. You might wish to invoke
<command>VACUUM</command> to recover the wasted space.
</para>
</refsect1>
</para>
<para>
- Backslash characters (<literal>\</>) may be used in the
+ Backslash characters (<literal>\</>) can be used in the
<command>COPY</command> data to quote data characters that might
otherwise be taken as row or column delimiters. In particular, the
following characters <emphasis>must</> be preceded by a backslash if
<para>
Presently, all data values in a <command>COPY BINARY</command> file are
assumed to be in binary format (format code one). It is anticipated that a
-future extension may add a header field that allows per-column format codes
+future extension might add a header field that allows per-column format codes
to be specified.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_aggregate.sgml,v 1.36 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_aggregate.sgml,v 1.37 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- An aggregate function may provide an initial condition,
+ An aggregate function can provide an initial condition,
that is, an initial value for the internal state value.
This is specified and stored in the database as a value of type
<type>text</type>, but it must be a valid external representation
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.23 2006/09/16 00:30:17 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_cast.sgml,v 1.24 2007/01/31 23:26:03 momjian Exp $ -->
<refentry id="SQL-CREATECAST">
<refmeta>
</para>
<para>
- Two types may be <firstterm>binary compatible</firstterm>, which
+ Two types can be <firstterm>binary compatible</firstterm>, which
means that they can be converted into one another <quote>for
free</quote> without invoking any function. This requires that
corresponding values use the same internal representation. For
<listitem>
<para>
- The function used to perform the cast. The function name may
+ The function used to perform the cast. The function name can
be schema-qualified. If it is not, the function will be looked
up in the schema search path. The function's result data type must
match the target type of the cast. Its arguments are discussed below.
<listitem>
<para>
- Indicates that the cast may be invoked implicitly in assignment
+ Indicates that the cast can be invoked implicitly in assignment
contexts.
</para>
</listitem>
<listitem>
<para>
- Indicates that the cast may be invoked implicitly in any context.
+ Indicates that the cast can be invoked implicitly in any context.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
- Cast implementation functions may have one to three arguments.
+ Cast implementation functions can have one to three arguments.
The first argument type must be identical to the cast's source type.
The second argument,
if present, must be type <type>integer</>; it receives the type
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_conversion.sgml,v 1.18 2006/09/16 00:30:17 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_conversion.sgml,v 1.19 2007/01/31 23:26:03 momjian Exp $ -->
<refentry id="SQL-CREATECONVERSION">
<refmeta>
<para>
<command>CREATE CONVERSION</command> defines a new conversion between
- character set encodings. Conversion names may be used in the
+ character set encodings. Conversion names can be used in the
<function>convert</function> function
to specify a particular encoding conversion. Also, conversions that
are marked <literal>DEFAULT</> can be used for automatic encoding
<listitem>
<para>
- The name of the conversion. The conversion name may be
+ The name of the conversion. The conversion name can be
schema-qualified. If it is not, the conversion is defined in the
current schema. The conversion name must be unique within a
schema.
<listitem>
<para>
- The function used to perform the conversion. The function name may
+ The function used to perform the conversion. The function name can
be schema-qualified. If it is not, the function will be looked
up in the path.
</para>
</para>
<para>
- The privileges required to create a conversion may be changed in a future
+ The privileges required to create a conversion might be changed in a future
release.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_database.sgml,v 1.46 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_database.sgml,v 1.47 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
database containing only the standard objects predefined by your
version of <productname>PostgreSQL</productname>. This is useful
if you wish to avoid copying
- any installation-local objects that may have been added to
+ any installation-local objects that might have been added to
<literal>template1</>.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.29 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_domain.sgml,v 1.30 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<term><replaceable class="PARAMETER">data_type</replaceable></term>
<listitem>
<para>
- The underlying data type of the domain. This may include array
+ The underlying data type of the domain. This can include array
specifiers.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.71 2007/01/22 01:35:19 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.72 2007/01/31 23:26:03 momjian Exp $
-->
<refentry id="SQL-CREATEFUNCTION">
specified schema. Otherwise it is created in the current schema.
The name of the new function must not match any existing function
with the same argument types in the same schema. However,
- functions of different argument types may share a name (this is
+ functions of different argument types can share a name (this is
called <firstterm>overloading</>).
</para>
<listitem>
<para>
The data type(s) of the function's arguments (optionally
- schema-qualified), if any. The argument types may be base, composite,
- or domain types, or may reference the type of a table column.
+ schema-qualified), if any. The argument types can be base, composite,
+ or domain types, or can reference the type of a table column.
</para>
<para>
- Depending on the implementation language it may also be allowed
+ Depending on the implementation language it might also be allowed
to specify <quote>pseudotypes</> such as <type>cstring</>.
Pseudotypes indicate that the actual argument type is either
incompletely specified, or outside the set of ordinary SQL data types.
<listitem>
<para>
The return data type (optionally schema-qualified). The return type
- may be a base, composite, or domain type,
- or may reference the type of a table column.
- Depending on the implementation language it may also be allowed
+ can be a base, composite, or domain type,
+ or can reference the type of a table column.
+ Depending on the implementation language it might also be allowed
to specify <quote>pseudotypes</> such as <type>cstring</>.
If the function is not supposed to return a value, specify
<type>void</> as the return type.
</para>
<para>
When there are <literal>OUT</> or <literal>INOUT</> parameters,
- the <literal>RETURNS</> clause may be omitted. If present, it
+ the <literal>RETURNS</> clause can be omitted. If present, it
must agree with the result type implied by the output parameters:
<literal>RECORD</> if there are multiple output parameters, or
the same type as the single output parameter.
<listitem>
<para>
The name of the language that the function is implemented in.
- May be <literal>SQL</literal>, <literal>C</literal>,
+ Can be <literal>SQL</literal>, <literal>C</literal>,
<literal>internal</literal>, or the name of a user-defined
procedural language. For backward compatibility,
- the name may be enclosed by single quotes.
+ the name can be enclosed by single quotes.
</para>
</listitem>
</varlistentry>
<para>
These attributes inform the query optimizer about the behavior
of the function. At most one choice
- may be specified. If none of these appear,
+ can be specified. If none of these appear,
<literal>VOLATILE</literal> is the default assumption.
</para>
<listitem>
<para>
A string constant defining the function; the meaning depends on the
- language. It may be an internal function name, the path to an
+ language. It can be an internal function name, the path to an
object file, an SQL command, or text in a procedural language.
</para>
</listitem>
<listitem>
<para>
The historical way to specify optional pieces of information
- about the function. The following attributes may appear here:
+ about the function. The following attributes can appear here:
<variablelist>
<varlistentry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_index.sgml,v 1.59 2007/01/09 02:14:10 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_index.sgml,v 1.60 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- The expression used in the <literal>WHERE</literal> clause may refer
+ The expression used in the <literal>WHERE</literal> clause can refer
only to columns of the underlying table, but it can use all columns,
not just the ones being indexed. Presently, subqueries and
aggregate expressions are also forbidden in <literal>WHERE</literal>.
<para>
An expression based on one or more columns of the table. The
expression usually must be written with surrounding parentheses,
- as shown in the syntax. However, the parentheses may be omitted
+ as shown in the syntax. However, the parentheses can be omitted
if the expression has the form of a function call.
</para>
</listitem>
significantly longer to complete. However, since it allows normal
operations to continue while the index is built, this method is useful for
adding new indexes in a production environment. Of course, the extra CPU
- and I/O load imposed by the index creation may slow other operations.
+ and I/O load imposed by the index creation might slow other operations.
</para>
<para>
If a problem arises during the second scan of the table, such as a
uniqueness violation in a unique index, the <command>CREATE INDEX</>
command will fail but leave behind an <quote>invalid</> index. This index
- will be ignored for querying purposes because it may be incomplete;
+ will be ignored for querying purposes because it might be incomplete;
however it will still consume update overhead. The recommended recovery
method in such cases is to drop the index and try again to perform
<command>CREATE INDEX CONCURRENTLY</>. (Another possibility is to rebuild
<para>
Currently, only the B-tree and GiST index methods support
- multicolumn indexes. Up to 32 fields may be specified by default.
+ multicolumn indexes. Up to 32 fields can be specified by default.
(This limit can be altered when building
<productname>PostgreSQL</productname>.) Only B-tree currently
supports unique indexes.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_language.sgml,v 1.42 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_language.sgml,v 1.43 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- For backward compatibility, the name may be enclosed by single
+ For backward compatibility, the name can be enclosed by single
quotes.
</para>
</listitem>
To create functions in a procedural language, a user must have the
<literal>USAGE</literal> privilege for the language. By default,
<literal>USAGE</> is granted to <literal>PUBLIC</> (i.e., everyone)
- for trusted languages. This may be revoked if desired.
+ for trusted languages. This can be revoked if desired.
</para>
<para>
in <structname>pg_pltemplate</>. But when there is an entry,
the functions need not already exist;
they will be automatically defined if not present in the database.
- (This can result in <command>CREATE LANGUAGE</> failing, if the
+ (This might result in <command>CREATE LANGUAGE</> failing, if the
shared library that implements the language is not available in
the installation.)
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_opclass.sgml,v 1.19 2007/01/23 05:07:17 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_opclass.sgml,v 1.20 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<term><replaceable class="parameter">name</replaceable></term>
<listitem>
<para>
- The name of the operator class to be created. The name may be
+ The name of the operator class to be created. The name can be
schema-qualified.
</para>
</listitem>
In an <literal>OPERATOR</> clause,
the operand data type(s) of the operator, or <literal>NONE</> to
signify a left-unary or right-unary operator. The operand data
- types may be omitted in the normal case where they are the same
+ types can be omitted in the normal case where they are the same
as the operator class's data type.
</para>
<para>
The <literal>OPERATOR</>, <literal>FUNCTION</>, and <literal>STORAGE</>
- clauses may appear in any order.
+ clauses can appear in any order.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.46 2006/12/23 00:43:08 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.47 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
The name of the operator to be defined. See above for allowable
- characters. The name may be schema-qualified, for example
+ characters. The name can be schema-qualified, for example
<literal>CREATE OPERATOR myschema.+ (...)</>. If not, then
the operator is created in the current schema. Two operators
in the same schema can have the same name if they operate on
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_opfamily.sgml,v 1.1 2007/01/23 05:07:17 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_opfamily.sgml,v 1.2 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<term><replaceable class="parameter">name</replaceable></term>
<listitem>
<para>
- The name of the operator family to be created. The name may be
+ The name of the operator family to be created. The name can be
schema-qualified.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_role.sgml,v 1.8 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_role.sgml,v 1.9 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- Note that older clients may lack support for the MD5
+ Note that older clients might lack support for the MD5
authentication mechanism that is needed to work with passwords
that are stored encrypted.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.48 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.49 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
Any <acronym>SQL</acronym> conditional expression (returning
- <type>boolean</type>). The condition expression may not refer
+ <type>boolean</type>). The condition expression cannot refer
to any tables except <literal>NEW</> and <literal>OLD</>, and
- may not contain aggregate functions.
+ can not contain aggregate functions.
</para>
</listitem>
</varlistentry>
<para>
Within <replaceable class="parameter">condition</replaceable> and
<replaceable class="parameter">command</replaceable>, the special
- table names <literal>NEW</literal> and <literal>OLD</literal> may
+ table names <literal>NEW</literal> and <literal>OLD</literal> can
be used to refer to values in the referenced table.
<literal>NEW</literal> is valid in <literal>ON INSERT</literal> and
<literal>ON UPDATE</literal> rules to refer to the new row being
one <command>NOTIFY</command> event will be sent during the
<command>UPDATE</command>, whether or not there are any rows that
match the condition <literal>id = 42</literal>. This is an
- implementation restriction that may be fixed in future releases.
+ implementation restriction that might be fixed in future releases.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_schema.sgml,v 1.18 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_schema.sgml,v 1.19 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
A schema is essentially a namespace:
it contains named objects (tables, data types, functions, and operators)
- whose names may duplicate those of other objects existing in other
+ whose names can duplicate those of other objects existing in other
schemas. Named objects are accessed either by <quote>qualifying</>
their names with the schema name as a prefix, or by setting a search
path that includes the desired schema(s). A <literal>CREATE</> command
<para>
The name of the user who will own the schema. If omitted,
defaults to the user executing the command. Only superusers
- may create schemas owned by users other than themselves.
+ can create schemas owned by users other than themselves.
</para>
</listitem>
</varlistentry>
<para>
The SQL standard specifies that the subcommands in <command>CREATE
- SCHEMA</command> may appear in any order. The present
+ SCHEMA</command> can appear in any order. The present
<productname>PostgreSQL</productname> implementation does not
- handle all cases of forward references in subcommands; it may
+ handle all cases of forward references in subcommands; it might
sometimes be necessary to reorder the subcommands in order to avoid
forward references.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_sequence.sgml,v 1.45 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_sequence.sgml,v 1.46 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
If a schema name is given then the sequence is created in the
specified schema. Otherwise it is created in the current schema.
- Temporary sequences exist in a special schema, so a schema name may not be
+ Temporary sequences exist in a special schema, so a schema name cannot be
given when creating a temporary sequence.
The sequence name must be distinct from the name of any other sequence,
table, index, or view in the same schema.
to examine the parameters and current state of a sequence. In particular,
the <literal>last_value</> field of the sequence shows the last value
- allocated by any session. (Of course, this value may be obsolete
+ allocated by any session. (Of course, this value might be obsolete
by the time it's printed, if other sessions are actively doing
<function>nextval</> calls.)
</para>
Sequences are based on <type>bigint</> arithmetic, so the range
cannot exceed the range of an eight-byte integer
(-9223372036854775808 to 9223372036854775807). On some older
- platforms, there may be no compiler support for eight-byte
+ platforms, there might be no compiler support for eight-byte
integers, in which case sequences use regular <type>integer</>
arithmetic (range -2147483648 to +2147483647).
</para>
<para>
- Unexpected results may be obtained if a <replaceable
+ Unexpected results might be obtained if a <replaceable
class="parameter">cache</replaceable> setting greater than one is
used for a sequence object that will be used concurrently by
multiple sessions. Each session will allocate and cache successive
<para>
Furthermore, although multiple sessions are guaranteed to allocate
- distinct sequence values, the values may be generated out of
+ distinct sequence values, the values might be generated out of
sequence when all the sessions are considered. For example, with
a <replaceable class="parameter">cache</replaceable> setting of 10,
session A might reserve values 1..10 and return
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.105 2006/09/16 00:30:17 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.106 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
If a schema name is given (for example, <literal>CREATE TABLE
myschema.mytable ...</>) then the table is created in the specified
schema. Otherwise it is created in the current schema. Temporary
- tables exist in a special schema, so a schema name may not be given
+ tables exist in a special schema, so a schema name cannot be given
when creating a temporary table. The name of the table must be
distinct from the name of any other table, sequence, index, or view
in the same schema.
<term><replaceable class="PARAMETER">data_type</replaceable></term>
<listitem>
<para>
- The data type of the column. This may include array
+ The data type of the column. This can include array
specifiers. For more information on the data types supported by
<productname>PostgreSQL</productname>, refer to <xref
linkend="datatype">.
<listitem>
<para>
The <literal>UNIQUE</literal> constraint specifies that a
- group of one or more columns of a table may contain
+ group of one or more columns of a table can contain
only unique values. The behavior of the unique table constraint
is the same as that for column constraints, with the additional
capability to span multiple columns.
<listitem>
<para>
The primary key constraint specifies that a column or columns of a table
- may contain only unique (non-duplicate), nonnull values.
+ can contain only unique (non-duplicate), nonnull values.
Technically, <literal>PRIMARY KEY</literal> is merely a
combination of <literal>UNIQUE</> and <literal>NOT NULL</>, but
identifying a set of columns as primary key also provides
metadata about the design of the schema, as a primary key
implies that other tables
- may rely on this set of columns as a unique identifier for rows.
+ can rely on this set of columns as a unique identifier for rows.
</para>
<para>
raised and the insert or update does not alter the database. A
check constraint specified as a column constraint should
reference that column's value only, while an expression
- appearing in a table constraint may reference multiple columns.
+ appearing in a table constraint can reference multiple columns.
</para>
<para>
class="parameter">reftable</replaceable> is used. The
referenced columns must be the columns of a unique or primary
key constraint in the referenced table. Note that foreign key
- constraints may not be defined between temporary tables and
+ constraints cannot be defined between temporary tables and
permanent tables.
</para>
</para>
<para>
- If the referenced column(s) are changed frequently, it may be wise to
+ If the referenced column(s) are changed frequently, it might be wise to
add an index to the foreign key column so that referential actions
associated with the foreign key column can be performed more
efficiently.
This controls whether the constraint can be deferred. A
constraint that is not deferrable will be checked immediately
after every command. Checking of constraints that are
- deferrable may be postponed until the end of the transaction
+ deferrable can be postponed until the end of the transaction
(using the <xref linkend="sql-set-constraints" endterm="sql-set-constraints-title"> command).
<literal>NOT DEFERRABLE</literal> is the default. Only foreign
key constraints currently accept this clause. All other
<para>
The SQL standard says that <literal>CHECK</> column constraints
- may only refer to the column they apply to; only <literal>CHECK</>
- table constraints may refer to multiple columns.
+ can only refer to the column they apply to; only <literal>CHECK</>
+ table constraints can refer to multiple columns.
<productname>PostgreSQL</productname> does not enforce this
restriction; it treats column and table check constraints alike.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_tablespace.sgml,v 1.7 2006/10/31 01:52:31 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_tablespace.sgml,v 1.8 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
A tablespace allows superusers to define an alternative location on
the file system where the data files containing database objects
- (such as tables and indexes) may reside.
+ (such as tables and indexes) can reside.
</para>
<para>
<para>
The name of the user who will own the tablespace. If omitted,
defaults to the user executing the command. Only superusers
- may create tablespaces, but they can assign ownership of tablespaces
+ can create tablespaces, but they can assign ownership of tablespaces
to non-superusers.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.45 2006/10/23 18:10:32 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_trigger.sgml,v 1.46 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
completed (after constraints are checked and the
<command>INSERT</command>, <command>UPDATE</command>, or
<command>DELETE</command> has completed). If the trigger fires
- before the event, the trigger may skip the operation for the
+ before the event, the trigger can skip the operation for the
current row, or change the row being inserted (for
<command>INSERT</command> and <command>UPDATE</command> operations
only). If the trigger fires after the event, all changes, including
An optional comma-separated list of arguments to be provided to
the function when the trigger is executed. The arguments are
literal string constants. Simple names and numeric constants
- may be written here, too, but they will all be converted to
+ can be written here, too, but they will all be converted to
strings. Please check the description of the implementation
language of the trigger function about how the trigger arguments
- are accessible within the function; it may be different from
+ are accessible within the function; it might be different from
normal function arguments.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.66 2006/12/30 21:21:52 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.67 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
The second form of <command>CREATE TYPE</command> creates a new base type
- (scalar type). The parameters may appear in any order, not only that
+ (scalar type). The parameters can appear in any order, not only that
illustrated above, and most are optional. You must register
two or more functions (using <command>CREATE FUNCTION</command>) before
defining the type. The support functions
converts the type's external textual representation to the internal
representation used by the operators and functions defined for the type.
<replaceable class="parameter">output_function</replaceable>
- performs the reverse transformation. The input function may be
+ performs the reverse transformation. The input function can be
declared as taking one argument of type <type>cstring</type>,
or as taking three arguments of types
<type>cstring</type>, <type>oid</type>, <type>integer</type>.
input value. The function must still return NULL in this case, unless
it raises an error.
(This case is mainly meant to support domain input functions, which
- may need to reject NULL inputs.)
+ might need to reject NULL inputs.)
The output function must be
declared as taking one argument of the new data type.
The output function must return type <type>cstring</type>.
representation is in the machine's native byte order.) The receive
function should perform adequate checking to ensure that the value is
valid.
- The receive function may be declared as taking one argument of type
+ The receive function can be declared as taking one argument of type
<type>internal</type>, or as taking three arguments of types
<type>internal</type>, <type>oid</type>, <type>integer</type>.
The first argument is a pointer to a <type>StringInfo</type> buffer
input value. The function must still return NULL in this case, unless
it raises an error.
(This case is mainly meant to support domain receive functions, which
- may need to reject NULL inputs.)
+ might need to reject NULL inputs.)
Similarly, the optional
<replaceable class="parameter">send_function</replaceable> converts
from the internal representation to the external binary representation.
<para>
The optional flag <literal>PASSEDBYVALUE</literal> indicates that
values of this data type are passed by value, rather than by
- reference. You may not pass by value types whose internal
+ reference. You cannot pass by value types whose internal
representation is larger than the size of the <type>Datum</> type
(4 bytes on most machines, 8 bytes on a few).
</para>
main table, but the system will not try to compress it.
<literal>main</literal> allows compression, but discourages moving
the value out of the main table. (Data items with this storage
- strategy may still be moved out of the main table if there is no
+ strategy might still be moved out of the main table if there is no
other way to make a row fit, but they will be kept in the main
table preferentially over <literal>extended</literal> and
<literal>external</literal> items.)
</para>
<para>
- A default value may be specified, in case a user wants columns of the
+ A default value can be specified, in case a user wants columns of the
data type to default to something other than the null value.
Specify the default with the <literal>DEFAULT</literal> key word.
- (Such a default may be overridden by an explicit <literal>DEFAULT</literal>
+ (Such a default can be overridden by an explicit <literal>DEFAULT</literal>
clause attached to a particular column.)
</para>
the name of the new data type as the return type of the input function.
The shell type is implicitly created in this situation, and then it
can be referenced in the definitions of the remaining I/O functions.
- This approach still works, but is deprecated and may be disallowed in
+ This approach still works, but is deprecated and might be disallowed in
some future release. Also, to avoid accidentally cluttering
the catalogs with shell types as a result of simple typos in function
definitions, a shell type will only be made this way when the input
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_view.sgml,v 1.33 2006/09/18 19:54:01 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_view.sgml,v 1.34 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
If a schema name is given (for example, <literal>CREATE VIEW
myschema.myview ...</>) then the view is created in the specified
schema. Otherwise it is created in the current schema. Temporary
- views exist in a special schema, so a schema name may not be given
+ views exist in a special schema, so a schema name cannot be given
when creating a temporary view. The name of the view must be
distinct from the name of any other view, table, sequence, or index
in the same schema.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/declare.sgml,v 1.39 2006/09/18 19:54:01 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/declare.sgml,v 1.40 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<command>SELECT</> would produce. Since data is stored natively in
binary format, the system must do a conversion to produce the text
format. Once the information comes back in text form, the client
- application may need to convert it to a binary format to manipulate
+ application might need to convert it to a binary format to manipulate
it. In addition, data in the text format is often larger in size
than in the binary format. Binary cursors return the data in a
- binary representation that may be more easily manipulated.
+ binary representation that might be more easily manipulated.
Nevertheless, if you intend to display the data as text anyway,
retrieving it in text form will
save you some effort on the client side.
<term><literal>NO SCROLL</literal></term>
<listitem>
<para>
- <literal>SCROLL</literal> specifies that the cursor may be used
+ <literal>SCROLL</literal> specifies that the cursor can be used
to retrieve rows in a nonsequential fashion (e.g.,
backward). Depending upon the complexity of the query's
- execution plan, specifying <literal>SCROLL</literal> may impose
+ execution plan, specifying <literal>SCROLL</literal> might impose
a performance penalty on the query's execution time.
<literal>NO SCROLL</literal> specifies that the cursor cannot be
used to retrieve rows in a nonsequential fashion. The default is to
<term><literal>WITHOUT HOLD</literal></term>
<listitem>
<para>
- <literal>WITH HOLD</literal> specifies that the cursor may
+ <literal>WITH HOLD</literal> specifies that the cursor can
continue to be used after the transaction that created it
successfully commits. <literal>WITHOUT HOLD</literal> specifies
that the cursor cannot be used outside of the transaction that
<para>
The key words <literal>BINARY</literal>,
- <literal>INSENSITIVE</literal>, and <literal>SCROLL</literal> may
+ <literal>INSENSITIVE</literal>, and <literal>SCROLL</literal> can
appear in any order.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.28 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.29 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
An expression to be computed and returned by the <command>DELETE</>
- command after each row is deleted. The expression may use any
+ command after each row is deleted. The expression can use any
column names of the <replaceable class="PARAMETER">table</replaceable>
or table(s) listed in <literal>USING</>.
Write <literal>*</> to return all columns.
<productname>PostgreSQL</productname> lets you reference columns of
other tables in the <literal>WHERE</> condition by specifying the
other tables in the <literal>USING</literal> clause. For example,
- to delete all films produced by a given producer, one might do
+ to delete all films produced by a given producer, one can do
<programlisting>
DELETE FROM films USING producers
WHERE producer_id = producers.id AND producers.name = 'foo';
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/drop_conversion.sgml,v 1.10 2006/09/16 00:30:18 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/drop_conversion.sgml,v 1.11 2007/01/31 23:26:03 momjian Exp $ -->
<refentry id="SQL-DROPCONVERSION">
<refmeta>
<listitem>
<para>
- The name of the conversion. The conversion name may be
+ The name of the conversion. The conversion name can be
schema-qualified.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_function.sgml,v 1.32 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_function.sgml,v 1.33 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
function. To execute this command the user must be the
owner of the function. The argument types to the
function must be specified, since several different functions
- may exist with the same name and different argument lists.
+ can exist with the same name and different argument lists.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_language.sgml,v 1.23 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_language.sgml,v 1.24 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
The name of an existing procedural language. For backward
- compatibility, the name may be enclosed by single quotes.
+ compatibility, the name can be enclosed by single quotes.
</para>
</listitem>
</varlistentry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_opclass.sgml,v 1.11 2007/01/23 05:07:17 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_opclass.sgml,v 1.12 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
containing the class, even if there is nothing else left in the
family (in particular, in the case where the family was implicitly
created by <command>CREATE OPERATOR CLASS</>). An empty operator
- family is harmless, but for the sake of tidiness you may wish to
+ family is harmless, but for the sake of tidiness you might wish to
remove the family with <command>DROP OPERATOR FAMILY</>; or perhaps
better, use <command>DROP OPERATOR FAMILY</> in the first place.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_owned.sgml,v 1.4 2006/09/18 21:19:29 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_owned.sgml,v 1.5 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- Using the <literal>CASCADE</literal> option may make the command
+ Using the <literal>CASCADE</literal> option might make the command
recurse to objects owned by other users.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_table.sgml,v 1.25 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_table.sgml,v 1.26 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
<command>DROP TABLE</command> removes tables from the database.
- Only its owner may destroy a table. To empty a table of rows
+ Only its owner can destroy a table. To empty a table of rows
without destroying the table, use <xref linkend="sql-delete"
endterm="sql-delete-title"> or <xref linkend="sql-truncate"
endterm="sql-truncate-title">.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_tablespace.sgml,v 1.5 2006/10/31 01:52:31 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_tablespace.sgml,v 1.6 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<para>
A tablespace can only be dropped by its owner or a superuser.
The tablespace must be empty of all database objects before it can be
- dropped. It is possible that objects in other databases may still reside
+ dropped. It is possible that objects in other databases might still reside
in the tablespace even if no objects in the current database are using
the tablespace.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.31 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.32 2007/01/31 23:26:03 momjian Exp $
PostgreSQL documentation
-->
<term><option>-C <replaceable>mode</replaceable></option></term>
<listitem>
<para>
- Set a compatibility mode. <replaceable>mode</replaceable> may
+ Set a compatibility mode. <replaceable>mode</replaceable> can
be <literal>INFORMIX</literal> or
<literal>INFORMIX_SE</literal>.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/explain.sgml,v 1.38 2006/09/18 19:54:01 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/explain.sgml,v 1.39 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
distribution of the data in the table has changed significantly
since the last time <command>ANALYZE</command> was run), the
estimated costs are unlikely to conform to the real properties of
- the query, and consequently an inferior query plan may be chosen.
+ the query, and consequently an inferior query plan might be chosen.
</para>
<para>
<para>
Of course, the specific numbers shown here depend on the actual
contents of the tables involved. Also note that the numbers, and
- even the selected query strategy, may vary between
+ even the selected query strategy, might vary between
<productname>PostgreSQL</productname> releases due to planner
improvements. In addition, the <command>ANALYZE</command> command
uses random sampling to estimate data statistics; therefore, it is
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/grant.sgml,v 1.62 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/grant.sgml,v 1.63 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
The key word <literal>PUBLIC</literal> indicates that the
- privileges are to be granted to all roles, including those that may
- be created later. <literal>PUBLIC</literal> may be thought of as an
+ privileges are to be granted to all roles, including those that might
+ be created later. <literal>PUBLIC</literal> can be thought of as an
implicitly defined group that always includes all roles.
Any particular role will have the sum
of privileges granted directly to it, privileges granted to any role it
<para>
If <literal>WITH GRANT OPTION</literal> is specified, the recipient
- of the privilege may in turn grant it to others. Without a grant
+ of the privilege can in turn grant it to others. Without a grant
option, the recipient cannot do that. Grant options cannot be granted
to <literal>PUBLIC</literal>.
</para>
</para>
<para>
- Depending on the type of object, the initial default privileges may
+ Depending on the type of object, the initial default privileges might
include granting some privileges to <literal>PUBLIC</literal>.
The default is no public access for tables, schemas, and tablespaces;
<literal>CONNECT</> privilege and <literal>TEMP</> table creation privilege
for databases;
<literal>EXECUTE</> privilege for functions; and
<literal>USAGE</> privilege for languages.
- The object owner may of course revoke these privileges. (For maximum
+ The object owner can of course revoke these privileges. (For maximum
security, issue the <command>REVOKE</> in the same transaction that
creates the object; then there is no window in which another user
- may use the object.)
+ can use the object.)
</para>
<para>
</para>
<para>
- If <literal>WITH ADMIN OPTION</literal> is specified, the member may
+ If <literal>WITH ADMIN OPTION</literal> is specified, the member can
in turn grant membership in the role to others, and revoke membership
in the role as well. Without the admin option, ordinary users cannot do
that. However,
If the <quote>Access privileges</> column is empty for a given object,
it means the object has default privileges (that is, its privileges column
is null). Default privileges always include all privileges for the owner,
-and may include some privileges for <literal>PUBLIC</> depending on the
+and can include some privileges for <literal>PUBLIC</> depending on the
object type, as explained above. The first <command>GRANT</> or
<command>REVOKE</> on an object
will instantiate the default privileges (producing, for example,
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/initdb.sgml,v 1.38 2007/01/06 19:40:00 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/initdb.sgml,v 1.39 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<command>initdb</command> must be run as the user that will own the
server process, because the server needs to have access to the
files and directories that <command>initdb</command> creates.
- Since the server may not be run as root, you must not run
+ Since the server cannot be run as root, you must not run
<command>initdb</command> as root either. (It will in fact refuse
to do so.)
</para>
<para>
By default, when <command>initdb</command>
determines that an error prevented it from completely creating the database
- cluster, it removes any files it may have created before discovering
+ cluster, it removes any files it might have created before discovering
that it can't finish the job. This option inhibits tidying-up and is
thus useful for debugging.
</para>
<listitem>
<para>
Specifies the directory where the database cluster is to be
- stored; may be overridden using the <option>-D</option> option.
+ stored; can be overridden using the <option>-D</option> option.
</para>
</listitem>
</varlistentry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/insert.sgml,v 1.34 2006/10/23 18:10:32 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/insert.sgml,v 1.35 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- The target column names may be listed in any order. If no list of
+ The target column names can be listed in any order. If no list of
column names is given at all, the default is all the columns of the
table in their declared order; or the first <replaceable>N</> column
names, if there are only <replaceable>N</> columns supplied by the
<listitem>
<para>
An expression to be computed and returned by the <command>INSERT</>
- command after each row is inserted. The expression may use any
+ command after each row is inserted. The expression can use any
column names of the <replaceable class="PARAMETER">table</replaceable>.
Write <literal>*</> to return all columns of the inserted row(s).
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/ipcclean.sgml,v 1.13 2006/09/16 00:30:18 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/ipcclean.sgml,v 1.14 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
The script makes assumptions about the output format of the
<command>ipcs</command>
- utility which may not be true across different operating systems.
- Therefore, it may not work on your particular OS. It's wise to
+ utility which might not be true across different operating systems.
+ Therefore, it might not work on your particular OS. It's wise to
look at the script before trying it.
</para>
</refsect1>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.23 2006/09/16 00:30:19 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.24 2007/01/31 23:26:04 momjian Exp $
-->
<refentry id="SQL-LOAD">
<para>
The file name is specified in the same way as for shared library
names in <xref linkend="sql-createfunction" endterm="sql-createfunction-title">; in particular, one
- may rely on a search path and automatic addition of the system's standard
+ can rely on a search path and automatic addition of the system's standard
shared library file name extension. See <xref linkend="xfunc-c"> for
more information on this topic.
</para>
</indexterm>
<para>
- Non-superusers may only apply <command>LOAD</> to library files
+ Non-superusers can only apply <command>LOAD</> to library files
located in <filename>$libdir/plugins/</> — the specified
<replaceable class="PARAMETER">filename</replaceable> must begin
with exactly that string. (It is the database administrator's
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/notify.sgml,v 1.28 2006/09/16 00:30:19 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/notify.sgml,v 1.29 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
<command>NOTIFY</command> behaves like Unix signals in one important
respect: if the same notification name is signaled multiple times in quick
- succession, recipients may get only one notification event for several executions
+ succession, recipients might get only one notification event for several executions
of <command>NOTIFY</command>. So it is a bad idea to depend on the number
of notifications received. Instead, use <command>NOTIFY</command> to wake up
applications that need to pay attention to something, and use a database
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/pg_config-ref.sgml,v 1.25 2006/10/23 18:10:32 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/pg_config-ref.sgml,v 1.26 2007/01/31 23:26:04 momjian Exp $ -->
<refentry id="app-pgconfig">
<refmeta>
<para>
Print the location of dynamically loadable modules, or where
the server would search for them. (Other
- architecture-dependent data files may also be installed in this
+ architecture-dependent data files might also be installed in this
directory.)
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/pg_controldata.sgml,v 1.8 2006/09/16 00:30:19 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/pg_controldata.sgml,v 1.9 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- This utility may only be run by the user who initialized the cluster because
+ This utility can only be run by the user who initialized the cluster because
it requires read access to the data directory.
You can specify the data directory on the command line, or use
the environment variable <envar>PGDATA</>.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/pg_ctl-ref.sgml,v 1.37 2007/01/11 02:30:01 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/pg_ctl-ref.sgml,v 1.38 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<listitem>
<para>
Specifies the shutdown mode. <replaceable>mode</replaceable>
- may be <literal>smart</literal>, <literal>fast</literal>, or
+ can be <literal>smart</literal>, <literal>fast</literal>, or
<literal>immediate</literal>, or the first letter of one of
these three.
</para>
<title>Notes</title>
<para>
- Waiting for complete start is not a well-defined operation and may
+ Waiting for complete start is not a well-defined operation and might
fail if access control is set up so that a local client cannot
connect without manual interaction (e.g., password authentication). For
additional connection variables, see <xref linkend="libpq-envars">,
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/pg_dump.sgml,v 1.92 2006/11/28 22:54:18 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/pg_dump.sgml,v 1.93 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
This option is only meaningful for the plain-text format. For
- the archive formats, you may specify the option when you
+ the archive formats, you can specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
<para>
This option is only meaningful for the plain-text format. For
- the archive formats, you may specify the option when you
+ the archive formats, you can specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
<para>
This option is only meaningful for the plain-text format. For
- the archive formats, you may specify the option when you
+ the archive formats, you can specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
an error in reloading a row causes only that row to be lost rather
than the entire table contents.
Note that
- the restore may fail altogether if you have rearranged column order.
+ the restore might fail altogether if you have rearranged column order.
The <option>-D</option> option is safe against column order changes,
though even slower.
</para>
<para>
When <option>-n</> is specified, <application>pg_dump</application>
makes no attempt to dump any other database objects that the selected
- schema(s) may depend upon. Therefore, there is no guarantee
+ schema(s) might depend upon. Therefore, there is no guarantee
that the results of a specific-schema dump can be successfully
restored by themselves into a clean database.
</para>
<para>
This option is only meaningful for the plain-text format. For
- the archive formats, you may specify the option when you
+ the archive formats, you can specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
<para>
When <option>-t</> is specified, <application>pg_dump</application>
makes no attempt to dump any other database objects that the selected
- table(s) may depend upon. Therefore, there is no guarantee
+ table(s) might depend upon. Therefore, there is no guarantee
that the results of a specific-table dump can be successfully
restored by themselves into a clean database.
</para>
<para>
This option is only meaningful for the plain-text format. For
- the archive formats, you may specify the option when you
+ the archive formats, you can specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
Output SQL-standard <command>SET SESSION AUTHORIZATION</> commands
instead of <command>ALTER OWNER</> commands to determine object
ownership. This makes the dump more standards compatible, but
- depending on the history of the objects in the dump, may not restore
+ depending on the history of the objects in the dump, might not restore
properly. Also, a dump using <command>SET SESSION AUTHORIZATION</>
will certainly require superuser privileges to restore correctly,
whereas <command>ALTER OWNER</> requires lesser privileges.
<application>pg_dump</application> emits commands to disable
triggers on user tables before inserting the data and commands
to re-enable them after the data has been inserted. If the
- restore is stopped in the middle, the system catalogs may be
+ restore is stopped in the middle, the system catalogs might be
left in the wrong state.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/pg_dumpall.sgml,v 1.63 2007/01/25 15:08:06 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/pg_dumpall.sgml,v 1.64 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
than <command>COPY</command>). This will make restoration very slow;
it is mainly useful for making dumps that can be loaded into
non-<productname>PostgreSQL</productname> databases. Note that
- the restore may fail altogether if you have rearranged column order.
+ the restore might fail altogether if you have rearranged column order.
The <option>-D</option> option is safer, though even slower.
</para>
</listitem>
Output SQL-standard <command>SET SESSION AUTHORIZATION</> commands
instead of <command>ALTER OWNER</> commands to determine object
ownership. This makes the dump more standards compatible, but
- depending on the history of the objects in the dump, may not restore
+ depending on the history of the objects in the dump, might not restore
properly.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.19 2006/12/08 19:50:52 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.20 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
After running this command, it should be possible to start the server,
- but bear in mind that the database may contain inconsistent data due to
+ but bear in mind that the database might contain inconsistent data due to
partially-committed transactions. You should immediately dump your data,
run <command>initdb</>, and reload. After reload, check for
inconsistencies and repair as needed.
valid data for <filename>pg_control</>, you can force it to proceed anyway
by specifying the <literal>-f</> (force) switch. In this case plausible
values will be substituted for the missing data. Most of the fields can be
- expected to match, but manual assistance may be needed for the next OID,
+ expected to match, but manual assistance might be needed for the next OID,
next transaction ID and epoch, next multitransaction ID and offset,
WAL starting address, and database locale fields.
The first six of these can be set using the switches discussed below.
epoch, next multitransaction ID, next multitransaction offset, and WAL
starting address values to be set manually. These are only needed when
<command>pg_resetxlog</command> is unable to determine appropriate values
- by reading <filename>pg_control</>. Safe values may be determined as
+ by reading <filename>pg_control</>. Safe values can be determined as
follows:
<itemizedlist>
<listitem>
<para>
A safe value for the next transaction ID (<literal>-x</>)
- may be determined by looking for the numerically largest
+ can be determined by looking for the numerically largest
file name in the directory <filename>pg_clog</> under the data directory,
adding one,
and then multiplying by 1048576. Note that the file names are in
<listitem>
<para>
A safe value for the next multitransaction ID (<literal>-m</>)
- may be determined by looking for the numerically largest
+ can be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/offsets</> under the
data directory, adding one, and then multiplying by 65536. As above,
the file names are in hexadecimal, so the easiest way to do this is to
<listitem>
<para>
A safe value for the next multitransaction offset (<literal>-O</>)
- may be determined by looking for the numerically largest
+ can be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/members</> under the
data directory, adding one, and then multiplying by 65536. As above,
the file names are in hexadecimal, so the easiest way to do this is to
The <literal>-n</> (no operation) switch instructs
<command>pg_resetxlog</command> to print the values reconstructed from
<filename>pg_control</> and then exit without modifying anything.
- This is mainly a debugging tool, but may be useful as a sanity check
+ This is mainly a debugging tool, but can be useful as a sanity check
before allowing <command>pg_resetxlog</command> to proceed for real.
</para>
</refsect1>
This command must not be used when the server is
running. <command>pg_resetxlog</command> will refuse to start up if
it finds a server lock file in the data directory. If the
- server crashed then a lock file may have been left
+ server crashed then a lock file might have been left
behind; in that case you can remove the lock file to allow
<command>pg_resetxlog</command> to run. But before you do
so, make doubly certain that there is no server process still alive.
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/pg_restore.sgml,v 1.64 2006/11/26 18:11:11 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/pg_restore.sgml,v 1.65 2007/01/31 23:26:04 momjian Exp $ -->
<refentry id="APP-PGRESTORE">
<refmeta>
<para>
Restore elements in <replaceable class="PARAMETER">
list-file</replaceable> only, and in the
- order they appear in the file. Lines can be moved and may also
+ order they appear in the file. Lines can be moved and can also
be commented out by placing a <literal>;</literal> at the
start of the line. (See below for examples.)
</para>
Output SQL-standard <command>SET SESSION AUTHORIZATION</> commands
instead of <command>ALTER OWNER</> commands to determine object
ownership. This makes the dump more standards compatible, but
- depending on the history of the objects in the dump, may not restore
+ depending on the history of the objects in the dump, might not restore
properly.
</para>
</listitem>
By default, table data is restored even if the creation command
for the table failed (e.g., because it already exists).
With this option, data for such a table is skipped.
- This behavior is useful when the target database may already
- contain the desired table contents. For example,
+ This behavior is useful if the target database already
+ contains the desired table contents. For example,
auxiliary tables for <productname>PostgreSQL</> extensions
- such as <productname>PostGIS</> may already be loaded in
+ such as <productname>PostGIS</> might already be loaded in
the target database; specifying this option prevents duplicate
or obsolete data from being loaded into them.
</para>
<application>pg_restore</application> emits commands
to disable triggers on user tables before inserting the data then emits commands to
re-enable them after the data has been inserted. If the restore is stopped in the
- middle, the system catalogs may be left in the wrong state.
+ middle, the system catalogs might be left in the wrong state.
</para>
</listitem>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/postgres-ref.sgml,v 1.48 2007/01/04 00:57:51 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/postgres-ref.sgml,v 1.49 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<title>Semi-internal Options</title>
<para>
- There are several other options that may be specified, used
+ There are several other options that can be specified, used
mainly for debugging purposes and in some cases to assist with
recovery of severely damaged databases. There should be no reason
to use them in a production database setup. These are listed
here only for the use by <productname>PostgreSQL</productname>
- system developers. Furthermore, any of these options may
- disappear or change in a future release without notice.
+ system developers. Furthermore, these options might
+ change or be removed in a future release without notice.
</para>
<variablelist>
<listitem>
<para>
- Default character encoding used by clients. (The clients may
+ Default character encoding used by clients. (The clients can
override this individually.) This value can also be set in the
configuration file.
</para>
A failure message mentioning <literal>semget</> or
<literal>shmget</> probably indicates you need to configure your
kernel to provide adequate shared memory and semaphores. For more
- discussion see <xref linkend="kernel-resources">. You may be able
+ discussion see <xref linkend="kernel-resources">. You might be able
to postpone reconfiguring your kernel by decreasing <xref
linkend="guc-shared-buffers"> to reduce the shared memory
consumption of <productname>PostgreSQL</>, and/or by reducing
<prompt>$</prompt> <userinput>ps -ef | grep postgres</userinput>
</screen>
depending on your system. If you are certain that no conflicting
- server is running, you may remove the lock file mentioned in the
+ server is running, you can remove the lock file mentioned in the
message and try again.
</para>
<para>
- A failure message indicating inability to bind to a port may
+ A failure message indicating inability to bind to a port might
indicate that that port is already in use by some
- non-<productname>PostgreSQL</productname> process. You may also
+ non-<productname>PostgreSQL</productname> process. You might also
get this error if you terminate <command>postgres</command>
and immediately restart it using the same port; in this case, you
must simply wait a few seconds until the operating system closes
- the port before trying again. Finally, you may get this error if
+ the port before trying again. Finally, you might get this error if
you specify a port number that your operating system considers to
be reserved. For example, many versions of Unix consider port
numbers under 1024 to be <quote>trusted</quote> and only permit
<command>postgres</command> server. Doing so will prevent
<command>postgres</command> from freeing the system
resources (e.g., shared memory and semaphores) that it holds before
- terminating. This may cause problems for starting a fresh
+ terminating. This might cause problems for starting a fresh
<command>postgres</command> run.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.21 2006/09/18 19:54:01 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.22 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
constant values in a statement to make guesses about the likely
result of executing the statement. Since this data is unavailable
when planning prepared statements with parameters, the chosen plan
- may be suboptimal. To examine the query plan
+ might be suboptimal. To examine the query plan
<productname>PostgreSQL</productname> has chosen for a prepared
statement, use <xref linkend="sql-explain"
endterm="sql-explain-title">.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.180 2007/01/20 16:57:31 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.181 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
</para>
<para>
- At the prompt, the user
may type in <acronym>SQL</acronym> commands.
+ At the prompt, the user
can type in <acronym>SQL</acronym> commands.
Ordinarily, input lines are sent to the server when a
command-terminating semicolon is reached. An end of line does not
terminate a command. Thus commands can be spread over several lines for
</para>
<para>
- To include whitespace into an argument you may quote it with a
+ To include whitespace into an argument you can quote it with a
single quote. To include a single quote into such an argument,
use two single quotes. Anything contained in single quotes is
furthermore subject to C-like substitutions for
This operation is not as efficient as the <acronym>SQL</acronym>
<command>COPY</command> command because all data must pass
through the client/server connection. For large
- amounts of data the <acronym>SQL</acronym> command may be preferable.
+ amounts of data the <acronym>SQL</acronym> command might be preferable.
</para>
</tip>
<tip>
<para>
If you use the <command>\o</command> command to redirect your
- query output you may wish to use <command>\qecho</command>
+ query output you might wish to use <command>\qecho</command>
instead of this command.
</para>
</tip>
<term><literal>tuples_only</literal> (or <literal>t</literal>)</term>
<listitem>
<para>
- Toggles between tuples only and full display. Full display may
- show extra information such as column headers, titles, and
+ Toggles between tuples only and full display. Full display
+ shows extra information such as column headers, titles, and
various footers. In tuples only mode, only actual table data
is shown.
</para>
<para>
The autocommit-on mode is <productname>PostgreSQL</>'s traditional
behavior, but autocommit-off is closer to the SQL spec. If you
- prefer autocommit-off, you may wish to set it in the system-wide
+ prefer autocommit-off, you might wish to set it in the system-wide
<filename>psqlrc</filename> file or your
<filename>~/.psqlrc</filename> file.
</para>
limited amount of memory is used, regardless of the size of
the result set. Settings of 100 to 1000 are commonly used
when enabling this feature.
- Keep in mind that when using this feature, a query may
+ Keep in mind that when using this feature, a query might
fail after having already displayed some rows.
</para>
<tip>
</para>
<para>
- Since colons may legally appear in SQL commands, the following rule
+ Since colons can legally appear in SQL commands, the following rule
applies: the character sequence
<quote>:name</quote> is not changed unless <quote>name</> is the name
of a variable that is currently set. In any case you can escape
<term><literal>%[</literal> ... <literal>%]</literal></term>
<listitem>
<para>
- Prompts may contain terminal control characters which, for
+ Prompts can contain terminal control characters which, for
example, change the color, background, or style of the prompt
text, or change the title of the terminal window. In order for
the line editing features of <application>Readline</application> to work properly, these
non-printing control characters must be designated as invisible
by surrounding them with <literal>%[</literal> and
- <literal>%]</literal>. Multiple pairs of these may occur within
+ <literal>%]</literal>. Multiple pairs of these can occur within
the prompt. For example,
<programlisting>
testdb=> \set PROMPT1 '%[%033[1;33;40m%]%n@%/%R%[%033[0m%]%# '
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/reindex.sgml,v 1.35 2007/01/05 01:18:59 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/reindex.sgml,v 1.36 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
<para>
An index has become corrupted, and no longer contains valid
data. Although in theory this should never happen, in
- practice indexes may become corrupted due to software bugs or
+ practice indexes can become corrupted due to software bugs or
hardware failures. <command>REINDEX</command> provides a
recovery method.
</para>
<listitem>
<para>
The name of the specific index, table, or database to be
- reindexed. Index and table names may be schema-qualified.
+ reindexed. Index and table names can be schema-qualified.
Presently, <command>REINDEX DATABASE</> and <command>REINDEX SYSTEM</>
can only reindex the current database, so their parameter must match
the current database's name.
Things are more difficult if you need to recover from corruption of
an index on a system table. In this case it's important for the
system to not have used any of the suspect indexes itself.
- (Indeed, in this sort of scenario you may find that server
+ (Indeed, in this sort of scenario you might find that server
processes are crashing immediately at start-up, due to reliance on
the corrupted indexes.) To recover safely, the server must be started
with the <option>-P</option> option, which prevents it from using
<application>libpq</>-based clients, it is possible to set
the <envar>PGOPTIONS</envar> environment variable to <literal>-P</>
before starting the client. Note that while this method does not
- require locking out other clients, it may still be wise to prevent
+ require locking out other clients, it might still be wise to prevent
other users from connecting to the damaged database until repairs
have been completed.
</para>
exclusive lock on the parent table, blocking both writes and reads. The
subsequent <command>CREATE INDEX</> locks out writes but not reads; since
the index is not there, no read will attempt to use it, meaning that there
- will be no blocking but reads may be forced into expensive sequential
+ will be no blocking but reads might be forced into expensive sequential
scans. Another important point is that the drop/create approach
invalidates any cached query plans that use the index, while
<command>REINDEX</> does not.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/release_savepoint.sgml,v 1.6 2006/09/16 00:30:19 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/release_savepoint.sgml,v 1.7 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
effects of commands executed after the savepoint was established.
(To do that, see <xref linkend="sql-rollback-to"
endterm="sql-rollback-to-title">.) Destroying a savepoint when
- it is no longer needed may allow the system to reclaim some resources
+ it is no longer needed allows the system to reclaim some resources
earlier than transaction end.
</para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/revoke.sgml,v 1.41 2006/09/16 00:30:19 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/revoke.sgml,v 1.42 2007/01/31 23:26:04 momjian Exp $
PostgreSQL documentation
-->
will fail. This recursive revocation only affects privileges that
were granted through a chain of users that is traceable to the user
that is the subject of this <literal>REVOKE</literal> command.
- Thus, the affected users may effectively keep the privilege if it
+ Thus, the affected users might effectively keep the privilege if it
was also granted through other users.
</para>
command, the command is performed as though it were issued by the
owner of the affected object. Since all privileges ultimately come
from the object owner (possibly indirectly via chains of grant options),
- it is possible for a superuser to revoke all privileges, but this may
+ it is possible for a superuser to revoke all privileges, but this might
require use of <literal>CASCADE</literal> as stated above.
</para>
indirectly via more than one role membership path, it is unspecified
which containing role will be used to perform the command. In such cases
it is best practice to use <command>SET ROLE</> to become the specific
- role you want to do the <command>REVOKE</> as. Failure to do so may
+ role you want to do the <command>REVOKE</> as. Failure to do so might
lead to revoking privileges other than the ones you intended, or not
revoking anything at all.
</para>
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result sets, but any function can be used.) This acts as
though its output were created as a temporary table for the
duration of this single <command>SELECT</command> command. An
- alias may also be used. If an alias is written, a column alias
+ alias can also be used. If an alias is written, a column alias
list can also be written to provide substitute names for one
or more attributes of the function's composite return type. If
the function has been defined as returning the <type>record</>
<literal>USING (<replaceable
class="parameter">join_column</replaceable> [, ...])</literal>.
See below for the meaning. For <literal>CROSS JOIN</literal>,
- none of these clauses may appear.
+ none of these clauses can appear.
</para>
<para>
</para>
<para>
- Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> may not be
+ Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> cannot be
specified either for a <literal>UNION</> result or for any input of a
<literal>UNION</>.
</para>
</para>
<para>
- Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> may not be
+ Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> cannot be
specified either for an <literal>INTERSECT</> result or for any input of
an <literal>INTERSECT</>.
</para>
</para>
<para>
- Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> may not be
+ Currently, <literal>FOR UPDATE</> and <literal>FOR SHARE</> cannot be
specified either for an <literal>EXCEPT</> result or for any input of
an <literal>EXCEPT</>.
</para>
</programlisting>
A limitation of this feature is that an <literal>ORDER BY</>
clause applying to the result of a <literal>UNION</>,
- <literal>INTERSECT</>, or <literal>EXCEPT</> clause may only
+ <literal>INTERSECT</>, or <literal>EXCEPT</> clause can only
specify an output column name or number, not an expression.
</para>
</para>
<para>
- Optionally one may add the key word <literal>ASC</> (ascending) or
+ Optionally one can add the key word <literal>ASC</> (ascending) or
<literal>DESC</> (descending) after any expression in the
<literal>ORDER BY</> clause. If not specified, <literal>ASC</> is
assumed by default. Alternatively, a specific ordering operator
- name may be specified in the <literal>USING</> clause.
+ name can be specified in the <literal>USING</> clause.
An ordering operator must be a less-than or greater-than
member of some btree operator family.
<literal>ASC</> is usually equivalent to <literal>USING <</> and
When using <literal>LIMIT</>, it is a good idea to use an
<literal>ORDER BY</> clause that constrains the result rows into a
unique order. Otherwise you will get an unpredictable subset of
- the query's rows — you may be asking for the tenth through
+ the query's rows — you might be asking for the tenth through
twentieth rows, but tenth through twentieth in what ordering? You
don't know what ordering unless you specify <literal>ORDER BY</>.
</para>
<title>Namespace Available to <literal>GROUP BY</literal> and <literal>ORDER BY</literal></title>
<para>
- In the SQL-92 standard, an <literal>ORDER BY</literal> clause may
+ In the SQL-92 standard, an <literal>ORDER BY</literal> clause can
only use result column names or numbers, while a <literal>GROUP
- BY</literal> clause may only use expressions based on input column
+ BY</literal> clause can only use expressions based on input column
names. <productname>PostgreSQL</productname> extends each of
these clauses to allow the other choice as well (but it uses the
standard's interpretation if there is ambiguity).
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/set_role.sgml,v 1.3 2006/09/16 00:30:20 momjian Exp $
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-->
<para>
This command sets the current user
identifier of the current SQL-session context to be <replaceable
- class="parameter">rolename</replaceable>. The role name may be
+ class="parameter">rolename</replaceable>. The role name can be
written as either an identifier or a string literal.
After <command>SET ROLE</>, permissions checking for SQL commands
is carried out as though the named role were the one that had logged
<para>
The <literal>NONE</> and <literal>RESET</> forms reset the current
user identifier to be the current session user identifier.
- These forms may be executed by any user.
+ These forms can be executed by any user.
</para>
</refsect1>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_session_auth.sgml,v 1.15 2006/09/16 00:30:20 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_session_auth.sgml,v 1.16 2007/01/31 23:26:04 momjian Exp $ -->
<refentry id="SQL-SET-SESSION-AUTHORIZATION">
<refmeta>
<refentrytitle id="sql-set-session-authorization-title">SET SESSION AUTHORIZATION</refentrytitle>
<para>
This command sets the session user identifier and the current user
identifier of the current SQL-session context to be <replaceable
- class="parameter">username</replaceable>. The user name may be
+ class="parameter">username</replaceable>. The user name can be
written as either an identifier or a string literal. Using this
command, it is possible, for example, to temporarily become an
unprivileged user and later switch back to being a superuser.
The session user identifier is initially set to be the (possibly
authenticated) user name provided by the client. The current user
identifier is normally equal to the session user identifier, but
- may change temporarily in the context of <quote>setuid</quote>
+ might change temporarily in the context of <quote>setuid</quote>
functions and similar mechanisms; it can also be changed by
<xref linkend="sql-set-role" endterm="sql-set-role-title">.
The current user identifier is relevant for permission checking.
</para>
<para>
- The session user identifier may be changed only if the initial session
+ The session user identifier can be changed only if the initial session
user (the <firstterm>authenticated user</firstterm>) had the
superuser privilege. Otherwise, the command is accepted only if it
specifies the authenticated user name.
<para>
The <literal>DEFAULT</> and <literal>RESET</> forms reset the session
and current user identifiers to be the originally authenticated user
- name. These forms may be executed by any user.
+ name. These forms can be executed by any user.
</para>
</refsect1>
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-->
issuing a <command>COMMIT</command> after each command that does not
follow <command>START TRANSACTION</> (or <command>BEGIN</command>),
and it is therefore often called <quote>autocommit</>.
- Other relational database systems may offer an autocommit feature
+ Other relational database systems might offer an autocommit feature
as a convenience.
</para>
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-->
<title>Notes</title>
<para>
- Only the owner of a table may <command>TRUNCATE</> it.
+ Only the owner of a table can <command>TRUNCATE</> it.
</para>
<para>
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-->
<title>Notes</title>
<para>
- You may unlisten something you were not listening for; no warning or error
+ You can unlisten something you were not listening for; no warning or error
will appear.
</para>
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-$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.41 2006/09/16 00:30:20 momjian Exp $
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-->
<term><replaceable class="PARAMETER">expression</replaceable></term>
<listitem>
<para>
- An expression to assign to the column. The expression may use the
+ An expression to assign to the column. The expression can use the
old values of this and other columns in the table.
</para>
</listitem>
<listitem>
<para>
An expression to be computed and returned by the <command>UPDATE</>
- command after each row is updated. The expression may use any
+ command after each row is updated. The expression can use any
column names of the <replaceable class="PARAMETER">table</replaceable>
or table(s) listed in <literal>FROM</>.
Write <literal>*</> to return all columns.
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-$PostgreSQL: pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.46 2007/01/31 04:13:22 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/vacuum.sgml,v 1.47 2007/01/31 23:26:04 momjian Exp $
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<term><literal>FULL</literal></term>
<listitem>
<para>
- Selects <quote>full</quote> vacuum, which may reclaim more
+ Selects <quote>full</quote> vacuum, which can reclaim more
space, but takes much longer and exclusively locks the table.
</para>
</listitem>
We recommend that active production databases be
vacuumed frequently (at least nightly), in order to
remove dead rows. After adding or deleting a large number
- of rows, it may be a good idea to issue a <command>VACUUM
+ of rows, it might be a good idea to issue a <command>VACUUM
ANALYZE</command> command for the affected table. This will update the
system catalogs with
the results of all recent changes, and allow the
<para>
The <option>FULL</option> option is not recommended for routine use,
- but may be useful in special cases. An example is when you have deleted
+ but might be useful in special cases. An example is when you have deleted
most of the rows in a table and would like the table to physically shrink
to occupy less disk space. <command>VACUUM FULL</command> will usually
shrink the table more than a plain <command>VACUUM</command> would.
<para>
<command>VACUUM</command> causes a substantial increase in I/O traffic,
- which can cause poor performance for other active sessions. Therefore,
+ which might cause poor performance for other active sessions. Therefore,
it is sometimes advisable to use the cost-based vacuum delay feature.
See <xref linkend="runtime-config-resource-vacuum-cost"> for details.
</para>
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-$PostgreSQL: pgsql/doc/src/sgml/ref/vacuumdb.sgml,v 1.37 2006/09/16 00:30:20 momjian Exp $
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-->
<listitem>
<para>
Clean or analyze <replaceable class="parameter">table</replaceable> only.
- Column names may be specified only in conjunction with
+ Column names can be specified only in conjunction with
the <option>--analyze</option> option.
</para>
<tip>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/values.sgml,v 1.2 2006/10/23 18:10:32 petere Exp $
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-->
<listitem>
<para>
An expression or integer constant indicating how to sort the result
- rows. This expression may refer to the columns of the
+ rows. This expression can refer to the columns of the
<command>VALUES</> result as <literal>column1</>, <literal>column2</>,
etc. For more details see
<xref linkend="sql-orderby" endterm="sql-orderby-title">.
<para>
<command>VALUES</> lists with very large numbers of rows should be avoided,
- as you may encounter out-of-memory failures or poor performance.
+ as you might encounter out-of-memory failures or poor performance.
<command>VALUES</> appearing within <command>INSERT</> is a special case
(because the desired column types are known from the <command>INSERT</>'s
target table, and need not be inferred by scanning the <command>VALUES</>
<para>
When <command>VALUES</> is used in <command>INSERT</>, the values are all
automatically coerced to the data type of the corresponding destination
- column. When it's used in other contexts, it may be necessary to specify
+ column. When it's used in other contexts, it might be necessary to specify
the correct data type. If the entries are all quoted literal constants,
coercing the first is sufficient to determine the assumed type for all:
projects / postgresql / commitdiff