From: Bruce Momjian <bruce@momjian.us>
Date: Fri, 4 Jan 2002 05:44:45 +0000 (+0000)
Subject: Update FAQ.
X-Git-Tag: REL7_2_BETA5~89
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0b79ed27457bda0f2545257225923488ca72a453;p=postgresql
Update FAQ.
---
diff --git a/doc/FAQ b/doc/FAQ
index a441646996..7d821c59c4 100644
--- a/doc/FAQ
+++ b/doc/FAQ
@@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Wed Dec 5 00:41:12 EST 2001
+ Last updated: Fri Jan 4 00:44:42 EST 2002
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@@ -58,42 +58,39 @@
Operational Questions
- 4.1) Why is the system confused about commas, decimal points, and date
- formats.
- 4.2) What is the exact difference between binary cursors and normal
- cursors?
- 4.3) How do I SELECT only the first few rows of a query?
- 4.4) How do I get a list of tables or other things I can see in psql?
- 4.5) How do you remove a column from a table?
- 4.6) What is the maximum size for a row, table, database?
- 4.7) How much database disk space is required to store data from a
+ 4.1) What is the difference between binary cursors and normal cursors?
+ 4.2) How do I SELECT only the first few rows of a query?
+ 4.3) How do I get a list of tables or other things I can see in psql?
+ 4.4) How do you remove a column from a table?
+ 4.5) What is the maximum size for a row, table, database?
+ 4.6) How much database disk space is required to store data from a
typical text file?
- 4.8) How do I find out what tables or indexes are defined in the
+ 4.7) How do I find out what tables or indexes are defined in the
database?
- 4.9) My queries are slow or don't make use of the indexes. Why?
- 4.10) How do I see how the query optimizer is evaluating my query?
- 4.11) What is an R-tree index?
- 4.12) What is the Genetic Query Optimizer?
- 4.13) How do I perform regular expression searches and
+ 4.8) My queries are slow or don't make use of the indexes. Why?
+ 4.9) How do I see how the query optimizer is evaluating my query?
+ 4.10) What is an R-tree index?
+ 4.11) What is the Genetic Query Optimizer?
+ 4.12) How do I perform regular expression searches and
case-insensitive regular expression searches? How do I use an index
for case-insensitive searches?
- 4.14) In a query, how do I detect if a field is NULL?
- 4.15) What is the difference between the various character types?
- 4.16.1) How do I create a serial/auto-incrementing field?
- 4.16.2) How do I get the value of a SERIAL insert?
- 4.16.3) Don't currval() and nextval() lead to a race condition with
+ 4.13) In a query, how do I detect if a field is NULL?
+ 4.14) What is the difference between the various character types?
+ 4.15.1) How do I create a serial/auto-incrementing field?
+ 4.15.2) How do I get the value of a SERIAL insert?
+ 4.15.3) Don't currval() and nextval() lead to a race condition with
other users?
- 4.17) What is an OID? What is a TID?
- 4.18) What is the meaning of some of the terms used in PostgreSQL?
- 4.19) Why do I get the error "ERROR: Memory exhausted in
+ 4.16) What is an OID? What is a TID?
+ 4.17) What is the meaning of some of the terms used in PostgreSQL?
+ 4.18) Why do I get the error "ERROR: Memory exhausted in
AllocSetAlloc()?"
- 4.20) How do I tell what PostgreSQL version I am running?
- 4.21) My large-object operations get invalid large obj descriptor.
+ 4.19) How do I tell what PostgreSQL version I am running?
+ 4.20) My large-object operations get invalid large obj descriptor.
Why?
- 4.22) How do I create a column that will default to the current time?
- 4.23) Why are my subqueries using IN so slow?
- 4.24) How do I perform an outer join?
- 4.25) How do I perform queries using multiple databases?
+ 4.21) How do I create a column that will default to the current time?
+ 4.22) Why are my subqueries using IN so slow?
+ 4.23) How do I perform an outer join?
+ 4.24) How do I perform queries using multiple databases?
Extending PostgreSQL
@@ -611,19 +608,11 @@
Operational Questions
- 4.1) Why is system confused about commas, decimal points, and date formats.
-
- Check your locale configuration. PostgreSQL uses the locale setting of
- the user that ran the postmaster process. There are postgres and psql
- SET commands to control the date format. Set those accordingly for
- your operating environment.
-
- 4.2) What is the exact difference between binary cursors and normal
- cursors?
+ 4.1) What is the difference between binary cursors and normal cursors?
See the DECLARE manual page for a description.
- 4.3) How do I SELECT only the first few rows of a query?
+ 4.2) How do I SELECT only the first few rows of a query?
See the FETCH manual page, or use SELECT ... LIMIT....
@@ -633,7 +622,7 @@
only the first few records requested, or the entire query may have to
be evaluated until the desired rows have been generated.
- 4.4) How do I get a list of tables or other things I can see in psql?
+ 4.3) How do I get a list of tables or other things I can see in psql?
You can read the source code for psql in file
pgsql/src/bin/psql/describe.c. It contains SQL commands that generate
@@ -641,7 +630,7 @@
the -E option so it will print out the queries it uses to execute the
commands you give.
- 4.5) How do you remove a column from a table?
+ 4.4) How do you remove a column from a table?
We do not support ALTER TABLE DROP COLUMN, but do this:
SELECT ... -- select all columns but the one you want to remove
@@ -650,7 +639,7 @@
DROP TABLE old_table;
ALTER TABLE new_table RENAME TO old_table;
- 4.6) What is the maximum size for a row, table, database?
+ 4.5) What is the maximum size for a row, table, database?
These are the limits:
Maximum size for a database? unlimited (60GB databases exist)
@@ -672,7 +661,7 @@
The maximum table size and maximum number of columns can be increased
if the default block size is increased to 32k.
- 4.7) How much database disk space is required to store data from a typical
+ 4.6) How much database disk space is required to store data from a typical
text file?
A PostgreSQL database may need six-and-a-half times the disk space
@@ -702,7 +691,7 @@
Indexes do not require as much overhead, but do contain the data that
is being indexed, so they can be large also.
- 4.8) How do I find out what tables or indexes are defined in the database?
+ 4.7) How do I find out what tables or indexes are defined in the database?
psql has a variety of backslash commands to show such information. Use
\? to see them.
@@ -711,7 +700,7 @@
many of the SELECTs needed to get information from the database system
tables.
- 4.9) My queries are slow or don't make use of the indexes. Why?
+ 4.8) My queries are slow or don't make use of the indexes. Why?
PostgreSQL does not automatically maintain statistics. VACUUM must be
run to update the statistics. After statistics are updated, the
@@ -736,11 +725,11 @@
string. So, to use indices, LIKE searches should not begin with %, and
~(regular expression searches) should start with ^.
- 4.10) How do I see how the query optimizer is evaluating my query?
+ 4.9) How do I see how the query optimizer is evaluating my query?
See the EXPLAIN manual page.
- 4.11) What is an R-tree index?
+ 4.10) What is an R-tree index?
An R-tree index is used for indexing spatial data. A hash index can't
handle range searches. A B-tree index only handles range searches in a
@@ -763,13 +752,13 @@
extending R-trees requires a bit of work and we don't currently have
any documentation on how to do it.
- 4.12) What is the Genetic Query Optimizer?
+ 4.11) What is the Genetic Query Optimizer?
The GEQO module speeds query optimization when joining many tables by
means of a Genetic Algorithm (GA). It allows the handling of large
join queries through nonexhaustive search.
- 4.13) How do I perform regular expression searches and case-insensitive
+ 4.12) How do I perform regular expression searches and case-insensitive
regular expression searches? How do I use an index for case-insensitive
searches?
@@ -788,11 +777,11 @@
CREATE INDEX tabindex on tab (lower(col));
- 4.14) In a query, how do I detect if a field is NULL?
+ 4.13) In a query, how do I detect if a field is NULL?
You test the column with IS NULLIS NOT NULL.
- 4.15) What is the difference between the various character types?
+ 4.14) What is the difference between the various character types?
Type Internal Name Notes
--------------------------------------------------
@@ -817,7 +806,7 @@ BYTEA bytea variable-length byte array (null-safe)
maximum 1 gigabyte. BYTEA is for storing binary data, particularly
values that include NULL bytes.
- 4.16.1) How do I create a serial/auto-incrementing field?
+ 4.15.1) How do I create a serial/auto-incrementing field?
PostgreSQL supports a SERIAL data type. It auto-creates a sequence and
index on the column. For example, this:
@@ -841,11 +830,11 @@ BYTEA bytea variable-length byte array (null-safe)
Numbering Rows.
- 4.16.2) How do I get the value of a SERIAL insert?
+ 4.15.2) How do I get the value of a SERIAL insert?
One approach is to to retrieve the next SERIAL value from the sequence
object with the nextval() function before inserting and then insert it
- explicitly. Using the example table in 4.16.1, that might look like
+ explicitly. Using the example table in 4.15.1, that might look like
this in Perl:
new_id = output of "SELECT nextval('person_id_seq')"
INSERT INTO person (id, name) VALUES (new_id, 'Blaise Pascal');
@@ -867,13 +856,13 @@ BYTEA bytea variable-length byte array (null-safe)
oid value is made available via $sth->{pg_oid_status} after
$sth->execute().
- 4.16.3) Don't currval() and nextval() lead to a race condition with other
+ 4.15.3) Don't currval() and nextval() lead to a race condition with other
users?
No. Currval() returns the current value assigned by your backend, not
by all users.
- 4.17) What is an OID? What is a TID?
+ 4.16) What is an OID? What is a TID?
OIDs are PostgreSQL's answer to unique row ids. Every row that is
created in PostgreSQL gets a unique OID. All OIDs generated during
@@ -906,7 +895,7 @@ BYTEA bytea variable-length byte array (null-safe)
values. Tids change after rows are modified or reloaded. They are used
by index entries to point to physical rows.
- 4.18) What is the meaning of some of the terms used in PostgreSQL?
+ 4.17) What is the meaning of some of the terms used in PostgreSQL?
Some of the source code and older documentation use terms that have
more common usage. Here are some:
@@ -923,7 +912,7 @@ BYTEA bytea variable-length byte array (null-safe)
A list of general database terms can be found at:
http://www.comptechnews.com/~reaster/dbdesign.html
- 4.19) Why do I get the error "ERROR: Memory exhausted in AllocSetAlloc()?"
+ 4.18) Why do I get the error "ERROR: Memory exhausted in AllocSetAlloc()?"
If you are running a version older than 7.1, an upgrade may fix the
problem. Also it is possible you have run out of virtual memory on
@@ -939,11 +928,11 @@ BYTEA bytea variable-length byte array (null-safe)
problem with the SQL client because the backend is returning too much
data, try it before starting the client.
- 4.20) How do I tell what PostgreSQL version I am running?
+ 4.19) How do I tell what PostgreSQL version I am running?
From psql, type select version();
- 4.21) My large-object operations get invalid large obj descriptor. Why?
+ 4.20) My large-object operations get invalid large obj descriptor. Why?
You need to put BEGIN WORK and COMMIT around any use of a large object
handle, that is, surrounding lo_open ... lo_close.
@@ -957,12 +946,12 @@ BYTEA bytea variable-length byte array (null-safe)
If you are using a client interface like ODBC you may need to set
auto-commit off.
- 4.22) How do I create a column that will default to the current time?
+ 4.21) How do I create a column that will default to the current time?
Use CURRENT_TIMESTAMP:
CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP );
- 4.23) Why are my subqueries using IN so slow?
+ 4.22) Why are my subqueries using IN so slow?
Currently, we join subqueries to outer queries by sequentially
scanning the result of the subquery for each row of the outer query. A
@@ -978,7 +967,7 @@ SELECT *
We hope to fix this limitation in a future release.
- 4.24) How do I perform an outer join?
+ 4.23) How do I perform an outer join?
PostgreSQL 7.1 and later supports outer joins using the SQL standard
syntax. Here are two examples:
@@ -1008,7 +997,7 @@ SELECT *
WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
ORDER BY col1
- 4.25) How do I perform queries using multiple databases?
+ 4.24) How do I perform queries using multiple databases?
There is no way to query any database except the current one. Because
PostgreSQL loads database-specific system catalogs, it is uncertain
diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html
index dd5eb71073..1133ab77d2 100644
--- a/doc/src/FAQ/FAQ.html
+++ b/doc/src/FAQ/FAQ.html
@@ -11,7 +11,7 @@
alink="#0000FF">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Wed Dec 5 00:41:12 EST 2001</P>
+ <P>Last updated: Fri Jan 4 00:44:42 EST 2002</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
@@ -89,57 +89,55 @@
<CENTER>
<H2>Operational Questions</H2>
</CENTER>
- <A href="#4.1">4.1</A>) Why is the system confused about commas,
- decimal points, and date formats.<BR>
- <A href="#4.2">4.2</A>) What is the exact difference between
+ <A href="#4.1">4.1</A>) What is the difference between
binary cursors and normal cursors?<BR>
- <A href="#4.3">4.3</A>) How do I <SMALL>SELECT</SMALL> only the
+ <A href="#4.2">4.2</A>) How do I <SMALL>SELECT</SMALL> only the
first few rows of a query?<BR>
- <A href="#4.4">4.4</A>) How do I get a list of tables or other
+ <A href="#4.3">4.3</A>) How do I get a list of tables or other
things I can see in <I>psql?</I><BR>
- <A href="#4.5">4.5</A>) How do you remove a column from a
+ <A href="#4.4">4.4</A>) How do you remove a column from a
table?<BR>
- <A href="#4.6">4.6</A>) What is the maximum size for a row, table,
+ <A href="#4.5">4.5</A>) What is the maximum size for a row, table,
database?<BR>
- <A href="#4.7">4.7</A>) How much database disk space is required
+ <A href="#4.6">4.6</A>) How much database disk space is required
to store data from a typical text file?<BR>
- <A href="#4.8">4.8</A>) How do I find out what tables or indexes
+ <A href="#4.7">4.7</A>) How do I find out what tables or indexes
are defined in the database?<BR>
- <A href="#4.9">4.9</A>) My queries are slow or don't make use of
+ <A href="#4.8">4.8</A>) My queries are slow or don't make use of
the indexes. Why?<BR>
- <A href="#4.10">4.10</A>) How do I see how the query optimizer is
+ <A href="#4.9">4.9</A>) How do I see how the query optimizer is
evaluating my query?<BR>
- <A href="#4.11">4.11</A>) What is an R-tree index?<BR>
- <A href="#4.12">4.12</A>) What is the Genetic Query Optimizer?<BR>
- <A href="#4.13">4.13</A>) How do I perform regular expression
+ <A href="#4.10">4.10</A>) What is an R-tree index?<BR>
+ <A href="#4.11">4.11</A>) What is the Genetic Query Optimizer?<BR>
+ <A href="#4.12">4.12</A>) How do I perform regular expression
searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?<BR>
- <A href="#4.14">4.14</A>) In a query, how do I detect if a field
+ <A href="#4.13">4.13</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>?<BR>
- <A href="#4.15">4.15</A>) What is the difference between the
+ <A href="#4.14">4.14</A>) What is the difference between the
various character types?<BR>
- <A href="#4.16.1">4.16.1</A>) How do I create a
+ <A href="#4.15.1">4.15.1</A>) How do I create a
serial/auto-incrementing field?<BR>
- <A href="#4.16.2">4.16.2</A>) How do I get the value of a
+ <A href="#4.15.2">4.15.2</A>) How do I get the value of a
<SMALL>SERIAL</SMALL> insert?<BR>
- <A href="#4.16.3">4.16.3</A>) Don't <I>currval()</I> and
+ <A href="#4.15.3">4.15.3</A>) Don't <I>currval()</I> and
<I>nextval()</I> lead to a race condition with other users?<BR>
- <A href="#4.17">4.17</A>) What is an <SMALL>OID</SMALL>? What is a
+ <A href="#4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is a
<SMALL>TID</SMALL>?<BR>
- <A href="#4.18">4.18</A>) What is the meaning of some of the terms
+ <A href="#4.17">4.17</A>) What is the meaning of some of the terms
used in PostgreSQL?<BR>
- <A href="#4.19">4.19</A>) Why do I get the error <I>"ERROR:
+ <A href="#4.18">4.18</A>) Why do I get the error <I>"ERROR:
Memory exhausted in AllocSetAlloc()?"</I><BR>
- <A href="#4.20">4.20</A>) How do I tell what PostgreSQL version I
+ <A href="#4.19">4.19</A>) How do I tell what PostgreSQL version I
am running? <BR>
- <A href="#4.21">4.21</A>) My large-object operations get
+ <A href="#4.20">4.20</A>) My large-object operations get
<I>invalid large obj descriptor.</I> Why?<BR>
- <A href="#4.22">4.22</A>) How do I create a column that will
+ <A href="#4.21">4.21</A>) How do I create a column that will
default to the current time?<BR>
- <A href="#4.23">4.23</A>) Why are my subqueries using
+ <A href="#4.22">4.22</A>) Why are my subqueries using
<CODE><SMALL>IN</SMALL></CODE> so slow?<BR>
- <A href="#4.24">4.24</A>) How do I perform an outer join?<BR>
- <A href="#4.25">4.25</A>) How do I perform queries using multiple databases?<BR>
+ <A href="#4.23">4.23</A>) How do I perform an outer join?<BR>
+ <A href="#4.24">4.24</A>) How do I perform queries using multiple databases?<BR>
<CENTER>
@@ -788,22 +786,13 @@
<H2>Operational Questions</H2>
</CENTER>
- <H4><A name="4.1">4.1</A>) Why is system confused about commas,
- decimal points, and date formats.</H4>
-
- <P>Check your locale configuration. PostgreSQL uses the locale
- setting of the user that ran the <I>postmaster</I> process. There
- are postgres and psql <SMALL>SET</SMALL> commands to control the
- date format. Set those accordingly for your operating
- environment.</P>
-
- <H4><A name="4.2">4.2</A>) What is the exact difference between
+ <H4><A name="4.1">4.1</A>) What is the difference between
binary cursors and normal cursors?</H4>
<P>See the <SMALL>DECLARE</SMALL> manual page for a
description.</P>
- <H4><A name="4.3">4.3</A>) How do I <SMALL>SELECT</SMALL> only the
+ <H4><A name="4.2">4.2</A>) How do I <SMALL>SELECT</SMALL> only the
first few rows of a query?</H4>
<P>See the <SMALL>FETCH</SMALL> manual page, or use
@@ -816,7 +805,7 @@
records requested, or the entire query may have to be evaluated
until the desired rows have been generated.</P>
- <H4><A name="4.4">4.4</A>) How do I get a list of tables or other
+ <H4><A name="4.3">4.3</A>) How do I get a list of tables or other
things I can see in <I>psql?</I><BR>
</H4>
@@ -827,7 +816,7 @@
<I>-E</I> option so it will print out the queries it uses to
execute the commands you give.</P>
- <H4><A name="4.5">4.5</A>) How do you remove a column from a
+ <H4><A name="4.4">4.4</A>) How do you remove a column from a
table?</H4>
<P>We do not support <SMALL>ALTER TABLE DROP COLUMN,</SMALL> but do
@@ -840,7 +829,7 @@
ALTER TABLE new_table RENAME TO old_table;
</PRE>
- <H4><A name="4.6">4.6</A>) What is the maximum size for a row,
+ <H4><A name="4.5">4.5</A>) What is the maximum size for a row,
table, database?</H4>
<P>These are the limits:</P>
@@ -864,7 +853,7 @@
<P>The maximum table size and maximum number of columns can be
increased if the default block size is increased to 32k.</P>
- <H4><A name="4.7">4.7</A>) How much database disk space is required
+ <H4><A name="4.6">4.6</A>) How much database disk space is required
to store data from a typical text file?<BR>
</H4>
@@ -897,7 +886,7 @@
<P>Indexes do not require as much overhead, but do contain the data
that is being indexed, so they can be large also.</P>
- <H4><A name="4.8">4.8</A>) How do I find out what tables or indexes
+ <H4><A name="4.7">4.7</A>) How do I find out what tables or indexes
are defined in the database?</H4>
<P><I>psql</I> has a variety of backslash commands to show such
@@ -907,7 +896,7 @@
illustrates many of the <SMALL>SELECT</SMALL>s needed to get
information from the database system tables.</P>
- <H4><A name="4.9">4.9</A>) My queries are slow or don't make use of
+ <H4><A name="4.8">4.8</A>) My queries are slow or don't make use of
the indexes. Why?</H4>
<P>PostgreSQL does not automatically maintain statistics.
@@ -937,12 +926,12 @@
<I>~</I>(regular expression searches) should start with
<I>^.</I></P>
- <H4><A name="4.10">4.10</A>) How do I see how the query optimizer
+ <H4><A name="4.9">4.9</A>) How do I see how the query optimizer
is evaluating my query?</H4>
<P>See the <SMALL>EXPLAIN</SMALL> manual page.</P>
- <H4><A name="4.11">4.11</A>) What is an R-tree index?</H4>
+ <H4><A name="4.10">4.10</A>) What is an R-tree index?</H4>
<P>An R-tree index is used for indexing spatial data. A hash index
can't handle range searches. A B-tree index only handles range
@@ -967,7 +956,7 @@
practice, extending R-trees requires a bit of work and we don't
currently have any documentation on how to do it.</P>
- <H4><A name="4.12">4.12</A>) What is the Genetic Query
+ <H4><A name="4.11">4.11</A>) What is the Genetic Query
Optimizer?</H4>
<P>The <SMALL>GEQO</SMALL> module speeds query optimization when
@@ -975,7 +964,7 @@
the handling of large join queries through nonexhaustive
search.</P>
- <H4><A name="4.13">4.13</A>) How do I perform regular expression
+ <H4><A name="4.12">4.12</A>) How do I perform regular expression
searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?</H4>
@@ -999,12 +988,12 @@
CREATE INDEX tabindex on tab (lower(col));
</PRE>
- <H4><A name="4.14">4.14</A>) In a query, how do I detect if a field
+ <H4><A name="4.13">4.13</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>?</H4>
<P>You test the column with <SMALL>IS NULL</SMALL>IS NOT NULL.</P>
- <H4><A name="4.15">4.15</A>) What is the difference between the
+ <H4><A name="4.14">4.14</A>) What is the difference between the
various character types?</H4>
<PRE>
Type Internal Name Notes
@@ -1034,7 +1023,7 @@ BYTEA bytea variable-length byte array (null-safe)
binary data, particularly values that include <SMALL>NULL</SMALL>
bytes.</P>
- <H4><A name="4.16.1">4.16.1</A>) How do I create a
+ <H4><A name="4.15.1">4.15.1</A>) How do I create a
serial/auto-incrementing field?</H4>
<P>PostgreSQL supports a <SMALL>SERIAL</SMALL> data type. It
@@ -1064,13 +1053,13 @@ BYTEA bytea variable-length byte array (null-safe)
<P><A href="http://www.PostgreSQL.org/docs/aw_pgsql_book">Numbering
Rows.</A></P>
- <H4><A name="4.16.2">4.16.2</A>) How do I get the value of a
+ <H4><A name="4.15.2">4.15.2</A>) How do I get the value of a
<SMALL>SERIAL</SMALL> insert?</H4>
<P>One approach is to to retrieve the next <SMALL>SERIAL</SMALL>
value from the sequence object with the <I>nextval()</I> function
<I>before</I> inserting and then insert it explicitly. Using the
- example table in <A href="#4.16.1">4.16.1</A>, that might look like
+ example table in <A href="#4.15.1">4.15.1</A>, that might look like
this in Perl:</P>
<PRE>
new_id = output of "SELECT nextval('person_id_seq')"
@@ -1091,20 +1080,20 @@ BYTEA bytea variable-length byte array (null-safe)
INSERT INTO person (name) VALUES ('Blaise Pascal');
new_id = output of "SELECT currval('person_id_seq')";
</PRE>
- Finally, you could use the <A href="#4.17"><SMALL>OID</SMALL></A>
+ Finally, you could use the <A href="#4.16"><SMALL>OID</SMALL></A>
returned from the <SMALL>INSERT</SMALL> statement to look up the
default value, though this is probably the least portable approach.
In Perl, using DBI with Edmund Mergl's DBD::Pg module, the oid
value is made available via <I>$sth->{pg_oid_status} after
$sth->execute().</I>
- <H4><A name="4.16.3">4.16.3</A>) Don't <I>currval()</I> and
+ <H4><A name="4.15.3">4.15.3</A>) Don't <I>currval()</I> and
<I>nextval()</I> lead to a race condition with other users?</H4>
<P>No. Currval() returns the current value assigned by your
backend, not by all users.</P>
- <H4><A name="4.17">4.17</A>) What is an <SMALL>OID</SMALL>? What is
+ <H4><A name="4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is
a <SMALL>TID</SMALL>?</H4>
<P><SMALL>OID</SMALL>s are PostgreSQL's answer to unique row ids.
@@ -1149,7 +1138,7 @@ BYTEA bytea variable-length byte array (null-safe)
or reloaded. They are used by index entries to point to physical
rows.</P>
- <H4><A name="4.18">4.18</A>) What is the meaning of some of the
+ <H4><A name="4.17">4.17</A>) What is the meaning of some of the
terms used in PostgreSQL?</H4>
<P>Some of the source code and older documentation use terms that
@@ -1178,7 +1167,7 @@ BYTEA bytea variable-length byte array (null-safe)
<P>A list of general database terms can be found at: <A href=
"http://www.comptechnews.com/~reaster/dbdesign.html">http://www.comptechnews.com/~reaster/dbdesign.html</A></P>
- <H4><A name="4.19">4.19</A>) Why do I get the error <I>"ERROR:
+ <H4><A name="4.18">4.18</A>) Why do I get the error <I>"ERROR:
Memory exhausted in AllocSetAlloc()?"</I><BR>
</H4>
@@ -1198,13 +1187,13 @@ BYTEA bytea variable-length byte array (null-safe)
backend is returning too much data, try it before starting the
client.
- <H4><A name="4.20">4.20</A>) How do I tell what PostgreSQL version
+ <H4><A name="4.19">4.19</A>) How do I tell what PostgreSQL version
I am running?<BR>
</H4>
<P>From <I>psql,</I> type <CODE>select version();</CODE></P>
- <H4><A name="4.21">4.21</A>) My large-object operations get
+ <H4><A name="4.20">4.20</A>) My large-object operations get
<I>invalid large obj descriptor.</I> Why?<BR>
</H4>
@@ -1221,7 +1210,7 @@ BYTEA bytea variable-length byte array (null-safe)
<P>If you are using a client interface like <SMALL>ODBC</SMALL> you
may need to set <CODE>auto-commit off.</CODE></P>
- <H4><A name="4.22">4.22</A>) How do I create a column that will
+ <H4><A name="4.21">4.21</A>) How do I create a column that will
default to the current time?<BR>
</H4>
@@ -1231,7 +1220,7 @@ BYTEA bytea variable-length byte array (null-safe)
</CODE>
</PRE>
- <H4><A name="4.23">4.23</A>) Why are my subqueries using
+ <H4><A name="4.22">4.22</A>) Why are my subqueries using
<CODE><SMALL>IN</SMALL></CODE> so slow?<BR>
</H4>
@@ -1254,7 +1243,7 @@ BYTEA bytea variable-length byte array (null-safe)
</PRE>
We hope to fix this limitation in a future release.
- <H4><A name="4.24">4.24</A>) How do I perform an outer join?<BR>
+ <H4><A name="4.23">4.23</A>) How do I perform an outer join?<BR>
</H4>
<P>PostgreSQL 7.1 and later supports outer joins using the SQL
@@ -1295,7 +1284,7 @@ BYTEA bytea variable-length byte array (null-safe)
ORDER BY col1
</PRE>
- <H4><A href="#4.25">4.25</A>) How do I perform queries
+ <H4><A href="#4.24">4.24</A>) How do I perform queries
using multiple databases?</H4>
<P>There is no way to query any database except the current one.