-.\" This is -*-nroff-*-
-.\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.7 2000/07/17 03:04:40 tgl Exp $
-.TH "SYSTEM CATALOGS" INTRO 03/13/94 PostgreSQL PostgreSQL
-.SH "Section 7 - System Catalogs"
-.de LS
-.PP
-.if n .ta 5 +13 +13
-.if t .ta 0.5i +1.3i +1.3i
-.in 0
-.nf
-..
-.de LE
-.fi
-.in
-..
-.SH "DESCRIPTION"
-In this
-section we list each of the attributes of the system catalogs and
-define their meanings.
-.SH "CLASS/TYPE SYSTEM CATALOGS"
-These catalogs form the core of the extensibility system:
-.LS
- \fBname\fP \fBshared/local\fP \fBdescription\fP
- pg_aggregate local aggregate functions
- pg_am local access methods
- pg_amop local operators usable with specific access methods
- pg_amproc local procedures used with specific access methods
- pg_attribute local class attributes
- pg_class local classes
- pg_index local indices
- pg_inherits local class inheritance hierarchy
- pg_language local procedure implementation languages
- pg_opclass local operator classes
- pg_operator local query language operators
- pg_proc local procedures (functions)
- pg_type local data types
-.LE
-.SH "ENTITIES"
-These catalogs deal with identification of entities known throughout
-the site:
-.LS
- \fBname\fP \fBshared/local\fP \fBdescription\fP
- pg_database shared current databases
- pg_group shared user groups
- pg_shadow shared valid users
-.LE
-.SH "RULE SYSTEM CATALOGS"
-.LS
- \fBname\fP \fBshared/local\fP \fBdescription\fP
- pg_listener local processes waiting on alerters
- pg_prs2plans local instance system procedures
- pg_prs2rule local instance system rules
- pg_prs2stub local instance system ``stubs''
- pg_rewrite local rewrite system information
-.LE
-.SH "LARGE OBJECT CATALOGS"
-.PP
-These catalogs are specific to the Inversion file system and large
-objects in general:
-.LS
- \fBname\fP \fBshared/local\fP \fBdescription\fP
- pg_lobj local description of a large object
- pg_naming local Inversion name space mapping
- pg_platter local jukebox platter inventory
- pg_plmap local jukebox platter extent map
-.LE
-.SH "INTERNAL CATALOGS"
-.PP
-These catalogs are internal classes that are not stored as normal
-heaps and cannot be accessed through normal means (attempting to do so
-causes an error).
-.LS
- \fBname\fP \fBshared/local\fP \fBdescription\fP
- pg_log shared transaction commit/rollback log
- pg_magic shared magic constant
- pg_time shared commit/rollback times
- pg_variable shared special variable values
-.LE
-.PP
-There are several other classes defined with \*(lqpg_\*(rq names.
-Aside from those that end in \*(lqind\*(rq (secondary indices), these
-are all obsolete or otherwise deprecated.
-.SH "CLASS/TYPE SYSTEM CATALOGS"
-.PP
-The following catalogs relate to the class/type system.
-.nf M
-/*
- * aggregates
- *
- * see DEFINE AGGREGATE for an explanation of transition functions
- */
-pg_aggregate
- NameData aggname /* aggregate name (e.g., "count") */
- oid aggowner /* usesysid of creator */
- regproc aggtransfn /* transition function */
- regproc aggfinalfn /* final function */
- oid aggbasetype /* type of data on which aggregate
- operates */
- oid aggtranstype /* type of aggregate's transition
- (state) data */
- oid aggfinaltype /* type of aggregate's final result */
- text agginitval /* external format of initial state value */
-.fi
-.nf M
-pg_am
- NameData amname /* access method name */
- oid amowner /* usesysid of creator */
- int2 amstrategies /* total NUMBER of strategies by which
- we can traverse/search this AM */
- int2 amsupport /* total NUMBER of support functions
- that this AM uses */
- int2 amorderstrategy /* if this AM has a sort order, the
- * strategy number of the sort operator.
- * Zero if AM is not ordered.
- */
- regproc amgettuple /* "next valid tuple" function */
- regproc aminsert /* "insert this tuple" function */
- regproc amdelete /* "delete this tuple" function */
- regproc amgetattr /* - deprecated */
- regproc amsetlock /* - deprecated */
- regproc amsettid /* - deprecated */
- regproc amfreetuple /* - deprecated */
- regproc ambeginscan /* "start new scan" function */
- regproc amrescan /* "restart this scan" function */
- regproc amendscan /* "end this scan" function */
- regproc ammarkpos /* "mark current scan position"
- function */
- regproc amrestrpos /* "restore marked scan position"
- function */
- regproc amopen /* - deprecated */
- regproc amclose /* - deprecated */
- regproc ambuild /* "build new index" function */
- regproc amcreate /* - deprecated */
- regproc amdestroy /* - deprecated */
- regproc amcostestimate /* estimate cost of an indexscan */
-
-.fi
-.nf M
-pg_amop
- oid amopid /* access method with which this
- operator be used */
- oid amopclaid /* operator class with which this
- operator can be used */
- oid amopopr /* the operator */
- int2 amopstrategy /* traversal/search strategy number
- to which this operator applies */
-.fi
-.nf M
-pg_amproc
- oid amid /* access method with which this
- procedure is associated */
- oid amopclaid /* operator class with which this
- operator can be used */
- oid amproc /* the procedure */
- int2 amprocnum /* support function number to which
- this operator applies */
-.fi
-.nf M
-pg_class
- NameData relname /* class name */
- oid relowner /* usesysid of owner */
- oid relam /* access method */
- int4 relpages /* # of 8KB pages */
- int4 reltuples /* # of instances */
- abstime relexpires /* time after which instances are
- deleted from non-archival storage */
- reltime relpreserved /* timespan after which instances are
- deleted from non-archival storage */
- bool relhasindex /* does the class have a secondary
- index? */
- bool relisshared /* is the class shared or local? */
- char relkind /* type of relation:
- i=index
- r=relation (heap)
- s=special
- u=uncatalogued (temporary) */
- char relarch /* archive mode:
- h=heavy
- l=light
- n=none */
- int2 relnatts /* current # of non-system
- attributes */
- int2 relsmgr /* storage manager:
- 0=magnetic disk
- 1=sony WORM jukebox
- 2=main memory */
- int2vector relkey /* - unused */
- oidvector relkeyop /* - unused */
- bool relhassubclass /* does the class have a subclass?
- */
- aclitem relacl[1] /* access control lists */
-.fi
-.nf M
-pg_attribute
- oid attrelid /* class containing this attribute */
- NameData attname /* attribute name */
- oid atttypid /* attribute type */
- oid attdefrel /* - deprecated */
- int4 attnvals /* - deprecated */
- oid atttyparg /* - deprecated */
- int2 attlen /* attribute length, in bytes
- -1=variable */
- int2 attnum /* attribute number
- >0=user attribute
- <0=system attribute */
- int2 attbound /* - deprecated */
- bool attbyval /* type passed by value? */
- bool attcanindex /* - deprecated */
- oid attproc /* - deprecated */
- int4 attnelems /* # of array dimensions */
- int4 attcacheoff /* cached offset into tuple */
- bool attisset /* is attribute set-valued? */
-.fi
-.nf M
-pg_inherits
- oid inhrel /* child class */
- oid inhparent /* parent class */
- int4 inhseqno /* - deprecated */
-.fi
-.nf M
- oid indexrelid /* oid of secondary index class */
- oid indrelid /* oid of indexed heap class */
- oid indproc /* function to compute index key from
- attribute(s) in heap
- 0=not a functional index */
- int2vector indkey /* attribute numbers of key
- attribute(s) */
- oidvector indclass /* opclass of each key */
- bool indisclustered /* is the index clustered?
- - unused */
- bool indisarchived /* is the index archival?
- - unused */
- text indpred /* query plan for partial index
- predicate */
-.fi
-.nf M
-pg_type
- NameData typname /* type name */
- oid typowner /* usesysid of owner */
- int2 typlen /* length in internal form
- -1=variable-length */
- int2 typprtlen /* length in external form */
- bool typbyval /* type passed by value? */
- char typtype /* kind of type:
- c=catalog (composite)
- b=base */
- bool typisdefined /* defined or still a shell? */
- char typdelim /* delimiter for array external form */
- oid typrelid /* class (if composite) */
- oid typelem /* type of each array element */
- regproc typinput /* external-internal conversion
- function */
- regproc typoutput /* internal-external conversion
- function */
- regproc typreceive /* client-server conversion function */
- regproc typsend /* server-client conversion function */
- text typdefault /* default value */
-.fi
-.nf M
-pg_operator
- NameData oprname /* operator name */
- oid oprowner /* usesysid of owner */
- int2 oprprec /* - deprecated */
- char oprkind /* kind of operator:
- b=binary
- l=left unary
- r=right unary */
- bool oprisleft /* is operator left/right associative? */
- bool oprcanhash /* is operator usable for hashjoin? */
- oid oprleft /* left operand type */
- oid oprright /* right operand type */
- oid oprresult /* result type */
- oid oprcom /* commutator operator */
- oid oprnegate /* negator operator */
- oid oprlsortop /* sort operator for left operand */
- oid oprrsortop /* sort operator for right operand */
- regproc oprcode /* function implementing this operator */
- regproc oprrest /* function to calculate operator
- restriction selectivity */
- regproc oprjoin /* function to calculate operator
- join selectivity */
-.fi
-.nf M
-pg_opclass
- NameData opcname /* operator class name */
-.fi
-.nf M
-pg_proc
- NameData proname /* function name */
- oid proowner /* usesysid of owner */
- oid prolang /* function implementation language */
- bool proisinh /* - deprecated */
- bool proistrusted /* run in server or untrusted function
- process? */
- bool proiscachable /* can the function return values be
- cached? */
- int2 pronargs /* # of arguments */
- bool proretset /* does the function return a set?
- - unused */
- oid prorettype /* return type */
- oidvector proargtypes /* argument types */
- int4 probyte_pct /* % of argument size (in bytes) that
- needs to be examined in order to
- compute the function */
- int4 properbyte_cpu /* sensitivity of the function's
- running time to the size of its
- inputs */
- int4 propercall_cpu /* overhead of the function's
- invocation (regardless of input
- size) */
- int4 prooutin_ratio /* size of the function's output as a
- percentage of the size of the input */
- text prosrc /* function definition:
- INTERNAL function: actual C name of function
- C function: currently, this field is unused
- SQL function: text of query(s)
- PL function: text in procedural language */
- bytea probin /* path to object file (C functions only) */
-.fi
-.nf M
-pg_language
- NameData lanname /* language name */
- text lancompiler /* - deprecated */
-.fi
-.SH "ENTITIES"
-.nf M
-pg_database
- NameData datname /* database name */
- oid datdba /* usesysid of database administrator */
- text datpath /* directory of database under
- $PGDATA */
-.fi
-.nf M
-pg_group
- NameData groname /* group name */
- int2 grosysid /* group's UNIX group id */
- int2 grolist[1] /* list of usesysids of group members */
-.fi
-.nf M
-pg_shadow
- NameData usename /* user's name */
- int2 usesysid /* user's UNIX user id */
- bool usecreatedb /* can user create databases? */
- bool usetrace /* can user set trace flags? */
- bool usesuper /* can user be POSTGRES superuser? */
- bool usecatupd /* can user update catalogs? */
-.fi
-.SH "RULE SYSTEM CATALOGS"
-.nf M
-pg_listener
- NameData relname /* class for which asynchronous
- notification is desired */
- int4 listenerpid /* process id of server corresponding
- to a frontend program waiting for
- asynchronous notification */
- int4 notification /* whether an event notification for
- this process id still pending */
-
-.fi
-.nf M
-pg_prs2rule
- NameData prs2name /* rule name */
- char prs2eventtype /* rule event type:
- R=retrieve
- U=update (replace)
- A=append
- D=delete */
- oid prs2eventrel /* class to which event applies */
- int2 prs2eventattr /* attribute to which event applies */
- float8 necessary /* - deprecated */
- float8 sufficient /* - deprecated */
- text prs2text /* text of original rule definition */
-.fi
-.nf M
-pg_prs2plans
- oid prs2ruleid /* prs2rule instance for which this
- plan is used */
- int2 prs2planno /* plan number (one rule may invoke
- multiple plans) */
- text prs2code /* external representation of the plan */
-.fi
-.nf M
-pg_prs2stub
- oid prs2relid /* class to which this rule applies */
- bool prs2islast /* is this the last stub fragment? */
- int4 prs2no /* stub fragment number */
- stub prs2stub /* stub fragment */
-.fi
-.nf M
-pg_rewrite
- NameData rulename /* rule name */
- char ev_type /* event type:
- RETRIEVE, REPLACE, APPEND, DELETE
- codes are parser-dependent (!?) */
- oid ev_class /* class to which this rule applies */
- int2 ev_attr /* attribute to which this rule applies */
- bool is_instead /* is this an "instead" rule? */
- text ev_qual /* qualification with which to modify
- (rewrite) the plan that triggered this
- rule */
- text action /* parse tree of action */
-.fi
-.SH "LARGE OBJECT CATALOGS"
-.nf M
-pg_lobj
- oid ourid /* 'ourid' from pg_naming that
- identifies this object in the
- Inversion file system namespace */
- int4 objtype /* storage type code:
- 0=Inversion
- 1=Unix
- 2=External
- 3=Jaquith */
- bytea object_descripto/* opaque object-handle structure */
-.fi
-.nf M
-pg_naming
- NameData filename /* filename component */
- oid ourid /* random oid used to identify this
- instance in other instances (can't
- use the actual oid for obscure
- reasons */
- oid parentid /* pg_naming instance of parent
- Inversion file system directory */
-.fi
-.nf M
-pg_platter
- NameData plname /* platter name */
- int4 plstart /* the highest OCCUPIED extent */
-.fi
-.nf M
-pg_plmap
- oid plid /* platter (in pg_platter) on which
- this extent (of blocks) resides */
- oid pldbid /* database of the class to which this
- extent (of blocks) belongs */
- oid plrelid /* class to which this extend (of
- blocks) belongs */
- int4 plblkno /* starting block number within the
- class */
- int4 ploffset /* offset within the platter at which
- this extent begins */
- int4 plextentsz /* length of this extent */
-.fi
+<!--
+ Documentation of the system catalogs, directed toward PostgreSQL developers
+ $Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.8 2000/11/29 20:15:58 petere Exp $
+ -->
+
+<chapter id="catalogs">
+ <title>System Catalogs</title>
+
+ <section id="catalogs-overview">
+ <title>Overview</title>
+
+ <para>
+ The system catalogs are the place where a relational database
+ management system stores schema metadata, such as information about
+ tables and columns, and internal bookkeeping information.
+ <productname>PostgreSQL</productname>'s system catalogs are regular
+ tables. You can drop and recreate the tables, add columns, insert
+ and update values, and severely mess up your system that way.
+ Normally one never has to change the system catalogs by hand, there
+ are always SQL commands to do that. (For example, <command>CREATE
+ DATABASE</command> inserts a row into the
+ <structname>pg_database</structname> catalog -- and actually
+ creates the database on disk.) There are some exceptions for
+ esoteric operations, such as adding index access methods.
+ </para>
+
+ <table>
+ <title>System Catalogs</title>
+
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Catalog Name</entry>
+ <entry>Purpose</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>pg_aggregate</entry>
+ <entry>aggregate functions</entry>
+ </row>
+
+ <row>
+ <entry>pg_am</entry>
+ <entry>index access methods</entry>
+ </row>
+
+ <row>
+ <entry>pg_amop</entry>
+ <entry>access method operators</entry>
+ </row>
+
+ <row>
+ <entry>pg_amproc</entry>
+ <entry>access method support procedures</entry>
+ </row>
+
+ <row>
+ <entry>pg_attrdef</entry>
+ <entry>column default values</entry>
+ </row>
+
+ <row>
+ <entry>pg_attribute</entry>
+ <entry>table columns (attributes, fields)</entry>
+ </row>
+
+ <row>
+ <entry>pg_class</entry>
+ <entry>tables, indexes, sequences (<quote>relations</quote>)</entry>
+ </row>
+
+ <row>
+ <entry>pg_database</entry>
+ <entry>databases</entry>
+ </row>
+
+ <row>
+ <entry>pg_description</entry>
+ <entry>descriptions or comments on database objects</entry>
+ </row>
+
+ <row>
+ <entry>pg_group</entry>
+ <entry>user groups</entry>
+ </row>
+
+ <row>
+ <entry>pg_index</entry>
+ <entry>additional index information</entry>
+ </row>
+
+ <row>
+ <entry>pg_inheritproc</entry>
+ <entry>(not used)</entry>
+ </row>
+
+ <row>
+ <entry>pg_inherits</entry>
+ <entry>table inheritance hierarchy</entry>
+ </row>
+
+ <row>
+ <entry>pg_ipl</entry>
+ <entry>(not used)</entry>
+ </row>
+
+ <row>
+ <entry>pg_language</entry>
+ <entry>languages for writing functions</entry>
+ </row>
+
+ <row>
+ <entry>pg_largeobject</entry>
+ <entry>large objects</entry>
+ </row>
+
+ <row>
+ <entry>pg_listener</entry>
+ <entry>asynchronous notification</entry>
+ </row>
+
+ <row>
+ <entry>pg_opclass</entry>
+ <entry>index access method operator classes</entry>
+ </row>
+
+ <row>
+ <entry>pg_operator</entry>
+ <entry>operators</entry>
+ </row>
+
+ <row>
+ <entry>pg_proc</entry>
+ <entry>functions and procedures</entry>
+ </row>
+
+ <row>
+ <entry>pg_relcheck</entry>
+ <entry>check constraints</entry>
+ </row>
+
+ <row>
+ <entry>pg_rewrite</entry>
+ <entry>query rewriter rules</entry>
+ </row>
+
+ <row>
+ <entry>pg_shadow</entry>
+ <entry>database users</entry>
+ </row>
+
+ <row>
+ <entry>pg_statistic</entry>
+ <entry>optimizer statistics</entry>
+ </row>
+
+ <row>
+ <entry>pg_trigger</entry>
+ <entry>triggers</entry>
+ </row>
+
+ <row>
+ <entry>pg_type</entry>
+ <entry>data types</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
+ More detailed documentation of most catalogs follow below. The
+ catalogs that relate to index access methods are explained in the
+ <citetitle>Programmer's Guide</citetitle>. Some catalogs don't
+ have any documentation, yet.
+ </para>
+
+ </section>
+
+
+ <section id="catalog-pg-aggregate">
+ <title>pg_aggregate</title>
+
+ <para>
+ <structname>pg_aggregate</structname> stores information about
+ aggregate functions. An aggregate function is a function that
+ operates on a set of values (typically one column from each the row
+ that matches a query condition) and returns a single value computed
+ from all these values. Typical aggregate functions are
+ <function>sum</function>, <function>count</function>, and
+ <function>max</function>.
+ </para>
+
+ <table>
+ <title>pg_aggregate Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>aggname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the aggregate function</entry>
+ </row>
+ <row>
+ <entry>aggowner</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner (creator) of the aggregate function</entry>
+ </row>
+ <row>
+ <entry>aggtransfn</entry>
+ <entry><type>regproc</type> (function)</entry>
+ <entry></entry>
+ <entry>Transition function</entry>
+ </row>
+ <row>
+ <entry>aggfinalfn</entry>
+ <entry><type>regproc</type> (function)</entry>
+ <entry></entry>
+ <entry>Final function</entry>
+ </row>
+ <row>
+ <entry>aggbasetype</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>The type on which this function operates when invoked from SQL</entry>
+ </row>
+ <row>
+ <entry>aggtranstype</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>The type of the aggregate function's internal transition (state) data</entry>
+ </row>
+ <row>
+ <entry>aggfinaltype</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>The type of the result</entry>
+ </row>
+ <row>
+ <entry>agginitval</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>
+ The initial value of the transition state. This is a text
+ field which will be cast to the type of aggtranstype.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
+ New aggregate functions are registered with the <command>CREATE
+ AGGREGATE</command> command. See the <citetitle>Programmer's
+ Guide</citetitle> for more information about writing aggregate
+ functions and the meaning of the transition functions, etc.
+ </para>
+
+ <para>
+ An aggregate function is identified through name
+ <emphasis>and</emphasis> argument type. Hence aggname and aggname
+ are the composite primary key.
+ </para>
+
+ </section>
+
+
+ <section id="catalog-pg-attrdef">
+ <title>pg_attrdef</title>
+
+ <para>
+ This catalog stores column default values. The main information
+ about columns is stored in <structname>pg_attribute</structname>
+ (see below). Only columns that explicitly specify a default value
+ (when the table is created or the column is added) will have an
+ entry here.
+ </para>
+
+ <table>
+ <title>pg_attrdef Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>adrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>The table this column belongs to</entry>
+ </row>
+
+ <row>
+ <entry>adnum</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ The number of the column; see
+ <structname>pg_attribute</structname>.<structfield>pg_attnum</structfield>
+ </entry>
+ </row>
+
+ <row>
+ <entry>adbin</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>An internal representation of the column default value</entry>
+ </row>
+
+ <row>
+ <entry>adsrc</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>A human-readable representation of the default value</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-attribute">
+ <title>pg_attribute</title>
+
+ <para>
+ <structname>pg_attribute</structname> stores information about
+ table columns. There will be exactly one
+ <structname>pg_attribute</structname> row for every column in every
+ table in the database. (There will also be attribute entries for
+ indexes and other objects. See <structname>pg_class</structname>.)
+ </para>
+
+ <para>
+ The term attribute is equivalent to column and is used for
+ historical reasons.
+ </para>
+
+ <table>
+ <title>pg_attribute Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>attrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>The table this column belongs to</entry>
+ </row>
+
+ <row>
+ <entry>attname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Column name</entry>
+ </row>
+
+ <row>
+ <entry>atttypid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>The data type of this column</entry>
+ </row>
+
+ <row>
+ <entry>attdispersion</entry>
+ <entry><type>float4</type></entry>
+ <entry></entry>
+ <entry>
+ <structfield>attdispersion</structfield> is the dispersion
+ statistic of the column (0.0 to 1.0), or zero if the statistic
+ has not been calculated, or -1.0 if <command>VACUUM</command>
+ found that the column contains no duplicate entries (in which
+ case the dispersion should be taken as
+ 1.0/<symbol>numberOfRows</symbol> for the current table size).
+ The -1.0 hack is useful because the number of rows may be
+ updated more often than
+ <structfield>attdispersion</structfield> is. We assume that the
+ column will retain its no-duplicate-entry property.
+ </entry>
+ </row>
+
+ <row>
+ <entry>attlen</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ This is a copy of the
+ <structname>pg_type</structname>.<structfield>typlen</structfield>
+ for this column's type.
+ </entry>
+ </row>
+
+ <row>
+ <entry>attnum</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ The number of the column. Ordinary columns are numbered from 1
+ up. System columns, such as <structfield>oid</structfield>,
+ have (arbitrary) negative numbers.
+ </entry>
+ </row>
+
+ <row>
+ <entry>attnelems</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>Number of dimensions, if the column is an array</entry>
+ </row>
+
+ <row>
+ <entry>attcacheoff</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>
+ Always -1 in storage, but when loaded into a tuple descriptor
+ in memory this may be updated cache the offset of the attribute
+ within the tuple.
+ </entry>
+ </row>
+
+ <row>
+ <entry>atttypmod</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>
+ <structfield>atttypmod</structfield> records type-specific data
+ supplied at table creation time (for example, the maximum
+ length of a <type>varchar</type> column). It is passed to
+ type-specific input and output functions as the third
+ argument. The value will generally be -1 for types that do not
+ need typmod.
+ </entry>
+ </row>
+
+ <row>
+ <entry>attbyval</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ A copy of
+ <structname>pg_type</structname>.<structfield>typbyval</structfield>
+ of this column's type
+ </entry>
+ </row>
+
+ <row>
+ <entry>attstorage</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>
+ A copy of
+ <structname>pg_type</structname>.<structfield>typstorage</structfield>
+ of this column's type
+ </entry>
+ </row>
+
+ <row>
+ <entry>attisset</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ If true, this attribute is a set. In that case, what is really
+ stored in the attribute is the OID of a tuple in the
+ <structname>pg_proc</structname> catalog. The
+ <structname>pg_proc</structname> tuple contains the query
+ string which defines this set - i.e., the query to run to get
+ the set. So the <structfield>atttypid</structfield> (see
+ above) refers to the type returned by this query, but the
+ actual length of this attribute is the length (size) of an
+ <type>oid</type>. --- At least this is the theory. All this
+ is probably quite broken these days.
+ </entry>
+ </row>
+
+ <row>
+ <entry>attalign</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>
+ A copy of
+ <structname>pg_type</structname>.<structfield>typalign</structfield>
+ of this column's type
+ </entry>
+ </row>
+
+ <row>
+ <entry>attnotnull</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ This represents a NOT NULL constraint. It is possible to
+ change this field to enable or disable the constraint.
+ </entry>
+ </row>
+
+ <row>
+ <entry>atthasdef</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ This column has a default value, in which case there will be a
+ corresponding entry in the <structname>pg_attrdef</structname>
+ catalog that actually defines the value.
+ </entry>
+ </row>
+
+ </tbody>
+ </tgroup>
+ </table>
+ </section>
+
+
+ <section id="catalog-pg-class">
+ <title>pg_class</title>
+
+ <para>
+ <structname>pg_class</structname> catalogues tables and mostly
+ everything else that has columns or is otherwise similar to a
+ table. This includes indexes (but see
+ <structname>pg_index</structname>), sequences, views, and some
+ kinds of special relation kinds. Below, when we mean all of these
+ kinds of objects we speak of <quote>relations</quote>. Not all
+ fields are meaningful for all relation types.
+ </para>
+
+ <table>
+ <title>pg_class Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>relname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the table, index, view, etc.</entry>
+ </row>
+
+ <row>
+ <entry>reltype</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>
+ The data type that corresponds to this table (not functional,
+ only set for system tables)
+ </entry>
+ </row>
+
+ <row>
+ <entry>relowner</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner of the relation</entry>
+ </row>
+
+ <row>
+ <entry>relam</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_am.oid</entry>
+ <entry>If this is an index, the access method used (btree, hash, etc.)</entry>
+ </row>
+
+ <row>
+ <entry>relfilenode</entry>
+ <entry><type>oid</type></entry>
+ <entry></entry>
+ <entry>Name of the on-disk file of this relation</entry>
+ </row>
+
+ <row>
+ <entry>relpages</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>
+ Size of the on-disk representation of this table in pages (size
+ <symbol>BLCKSZ</symbol>). This is only an approximate value
+ which is calculated during vacuum.
+ </entry>
+ </row>
+
+ <row>
+ <entry>reltuples</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>
+ Number of tuples in the table. This is only an estimate used
+ by the planner, updated by <command>VACUUM</command>.
+ </entry>
+ </row>
+
+ <row>
+ <entry>reltoastrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>
+ Oid of the TOAST table associated with this table, 0 if none.
+ The TOAST table stores large attributes <quote>out of
+ line</quote> in a secondary table.
+ </entry>
+ </row>
+
+ <row>
+ <entry>reltoastidxid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>Oid of the index on the TOAST table for this table, 0 if none</entry>
+ </row>
+
+ <row>
+ <entry>relhasindex</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>True if this is a table and it has at least one index</entry>
+ </row>
+
+ <row>
+ <entry>relisshared</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>XXX (This is not what it seems to be.)</entry>
+ </row>
+
+ <row>
+ <entry>relkind</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>
+ 'r' = ordinary table, 'i' = index, 'S' = sequence, 'v' = view,
+ 's' = special, 't' = secondary TOAST table
+ </entry>
+ </row>
+
+ <row>
+ <entry>relnatts</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ Number of columns in the relation, besides system columns.
+ There must be this many corresponding entries in
+ <structname>pg_attribute</structname>. See also
+ <structname>pg_attribute</structname>.<structfield>attnum</structfield>.
+ </entry>
+ </row>
+
+ <row>
+ <entry>relchecks</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ Number of check constraints on the table; see
+ <structname>pg_relcheck</structname> catalog
+ </entry>
+ </row>
+
+ <row>
+ <entry>reltriggers</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>
+ Number of triggers on the table; see
+ <structname>pg_trigger</structname> catalog
+ </entry>
+ </row>
+
+ <row>
+ <entry>relukeys</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>unused (<emphasis>Not</emphasis> the number of unique keys or something.)</entry>
+ </row>
+
+ <row>
+ <entry>relfkeys</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>Number foreign keys on the table</entry>
+ </row>
+
+ <row>
+ <entry>relhaspkey</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ unused (No, this does not say whether the table has a primary
+ key. It's really unused.)
+ </entry>
+ </row>
+
+ <row>
+ <entry>relhasrules</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>Table has rules</entry>
+ </row>
+
+ <row>
+ <entry>relhassubclass</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>At least one table inherits this one</entry>
+ </row>
+
+ <row>
+ <entry>relacl</entry>
+ <entry><type>aclitem[]</type></entry>
+ <entry></entry>
+ <entry>
+ Access permissions. See the descriptions of
+ <command>GRANT</command> and <command>REVOKE</command> for
+ details.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </section>
+
+
+ <section id="catalog-pg-database">
+ <title>pg_database</title>
+
+ <para>
+ The <structname>pg_database</structname> catalog stores information
+ about the available databases. The
+ <structname>pg_database</structname> table is shared between all
+ databases of a cluster. Databases are created with the
+ <command>CREATE DATABASE</command>. Consult the
+ <citetitle>Administrator's Guide</citetitle> for details about the
+ meaning of some of the parameters.
+ </para>
+
+ <table>
+ <title>pg_database Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>datname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Database name</entry>
+ </row>
+
+ <row>
+ <entry>datdba</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner of the database, initially who created it</entry>
+ </row>
+
+ <row>
+ <entry>encoding</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>Character/multibyte encoding for this database</entry>
+ </row>
+
+ <row>
+ <entry>datistemplate</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ If true then this database can be used in the
+ <quote>TEMPLATE</quote> clause of <command>CREATE
+ DATABASE</command> to create the new database as a clone of
+ this one.
+ </entry>
+ </row>
+
+ <row>
+ <entry>datallowconn</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ If false then no one can connect to this database. This is
+ used to protect the template0 database from being altered.
+ </entry>
+ </row>
+
+ <row>
+ <entry>datlastsysoid</entry>
+ <entry><type>oid</type></entry>
+ <entry></entry>
+ <entry>
+ Last oid in existence after the database was created; useful
+ particularly to <application>pg_dump</application>
+ </entry>
+ </row>
+
+ <row>
+ <entry>datpath</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>
+ If the database is stored at an alternative location then this
+ records the location. It's either an environment variable name
+ or an absolute path, depending how it was entered.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </section>
+
+
+ <section id="catalog-pg-description">
+ <title>pg_description</title>
+
+ <para>
+ The pg_description table can store an optional description or
+ comment for each database object. Descriptions can be manipulated
+ with the <command>COMMENT</command> command. Client applications
+ can view the descriptions by joining with this table. Many builtin
+ system objects have comments associated with them that are shown by
+ <application>psql</application>'s <literal>\d</literal> commands.
+ </para>
+
+ <table>
+ <title>pg_description Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>objoid</entry>
+ <entry><type>oid</type></entry>
+ <entry>any oid attribute</entry>
+ <entry>The oid of the object this description pertains to</entry>
+ </row>
+
+ <row>
+ <entry>description</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>Arbitrary text that serves as the description of this object.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-group">
+ <title>pg_group</title>
+
+ <para>
+ This catalog defines groups and stores what users belong to what
+ groups. Groups are created with the <command>CREATE
+ GROUP</command> command. Consult the <citetitle>Administrator's
+ Guide</citetitle> for information about user permission management.
+ </para>
+
+ <table>
+ <title>pg_group Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>groname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the group</entry>
+ </row>
+
+ <row>
+ <entry>grosysid</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>An arbitrary number to identify this group</entry>
+ </row>
+
+ <row>
+ <entry>grolist</entry>
+ <entry><type>int4[]</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>An array containing the ids of the users in this group</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-index">
+ <title>pg_index</title>
+
+ <para>
+ <structname>pg_index</structname> contains part of the information
+ about indexes. The rest is mostly in
+ <structname>pg_class</structname>.
+ </para>
+
+ <table>
+ <title>pg_index Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>indexrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>The oid of the pg_class entry for this index</entry>
+ </row>
+
+ <row>
+ <entry>indrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>The oid of the pg_class entry for the table this index is for</entry>
+ </row>
+
+ <row>
+ <entry>indproc</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_proc.oid</entry>
+ <entry>The registered procedure if this is a functional index</entry>
+ </row>
+
+ <row>
+ <entry>indkey</entry>
+ <entry><type>int2vector</type></entry>
+ <entry>pg_attribute.attnum</entry>
+ <entry>
+ This is an vector (array) of up to
+ <symbol>INDEX_MAX_KEYS</symbol> values that indicate which
+ table columns this index pertains to. For example a value of
+ <literal>1 3</literal> would mean that the first and the third
+ column make up the index key.
+ </entry>
+ </row>
+
+ <row>
+ <entry>indclass</entry>
+ <entry><type>oidvector</type></entry>
+ <entry>pg_opclass.oid</entry>
+ <entry>
+ For each column in the index key this contains a reference to
+ the <quote>operator class</quote> to use. See
+ <structname>pg_opclass</structname> for details.
+ </entry>
+ </row>
+
+ <row>
+ <entry>indisclustered</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>indislossy</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>???</entry>
+ </row>
+
+ <row>
+ <entry>indisunique</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>If true, this is a unique index.</entry>
+ </row>
+
+ <row>
+ <entry>indisprimary</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>If true, this index is a unique index that represents the primary key of the table.</entry>
+ </row>
+
+ <row>
+ <entry>indreference</entry>
+ <entry><type>oid</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>indpred</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>Query plan for partial index predicate (not functional)</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-inherits">
+ <title>pg_inherits</title>
+
+ <para>
+ This catalog records information about table inheritance hierarchies.
+ </para>
+
+ <table>
+ <title>pg_inherits Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>inhrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>
+ This is the reference to the subtable, that is, it records the
+ fact that the identified table is inherited from some other
+ table.
+ </entry>
+ </row>
+
+ <row>
+ <entry>inhparent</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>
+ This is the reference to the parent table, from which the table
+ referenced by <structfield>inhrelid</structfield> inherited
+ from.
+ </entry>
+ </row>
+
+ <row>
+ <entry>inhseqno</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>
+ If there is more than one subtable/parent pair (multiple
+ inheritance), this number tells the order in which the
+ inherited columns are to be arranged. The count starts at 1.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-language">
+ <title>pg_language</title>
+
+ <para>
+ <structname>pg_language</structname> registers call interfaces or
+ languages in which you can write functions or stored procedures.
+ See under <command>CREATE LANGUAGE</command> and in the
+ <citetitle>Programmer's Guide</citetitle> for more information
+ about language handlers.
+ </para>
+
+ <table>
+ <title>pg_language Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>lanname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the language (to be specified when creating a function)</entry>
+ </row>
+
+ <row>
+ <entry>lanispl</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ This is false for internal languages (such as SQL) and true for
+ dynamically loaded language handler modules. It essentially
+ means that, if it is true, the language may be dropped.
+ </entry>
+ </row>
+
+ <row>
+ <entry>lanpltrusted</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ This is a trusted language. See under <command>CREATE
+ LANGUAGE</command> what this means. If this is an internal
+ language (<structfield>lanispl</structfield> is false) then
+ this field is meaningless.
+ </entry>
+ </row>
+
+ <row>
+ <entry>lanplcallfoid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_proc.oid</entry>
+ <entry>
+ For non-internal languages this references the language
+ handler, which is a special function that is responsible for
+ executing all functions that are written in the particular
+ language.
+ </entry>
+ </row>
+
+ <row>
+ <entry>lancompiler</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>not useful</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-operator">
+ <title>pg_operator</title>
+
+ <para>
+ See <command>CREATE OPERATOR</command> and the
+ <citetitle>Programmer's Guide</citetitle> for details on these
+ operator parameters.
+ </para>
+
+ <table>
+ <title>pg_operator Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>oprname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the operator</entry>
+ </row>
+
+ <row>
+ <entry>oprowner</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner (creator) of the operator</entry>
+ </row>
+
+ <row>
+ <entry>oprprec</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>oprkind</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>
+ 'b' = infix (<quote>both</quote>), 'l' = prefix
+ (<quote>left</quote>), 'r' = postfix (<quote>right</quote>)
+ </entry>
+ </row>
+
+ <row>
+ <entry>oprisleft</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>oprcanhash</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>This operator supports hash joins.</entry>
+ </row>
+
+ <row>
+ <entry>oprleft</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>Type of the left operand</entry>
+ </row>
+
+ <row>
+ <entry>oprright</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>Type of the right operand</entry>
+ </row>
+
+ <row>
+ <entry>oprresult</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>Type of the result</entry>
+ </row>
+
+ <row>
+ <entry>oprcom</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_operator.oid</entry>
+ <entry>Commutator of this operator, if any</entry>
+ </row>
+
+ <row>
+ <entry>oprnegate</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_operator.oid</entry>
+ <entry>Inverse of this operator, if any</entry>
+ </row>
+
+ <row>
+ <entry>oprlsortop</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_operator.oid</entry>
+ <entry>
+ If this operator supports merge joins, the operator that sorts
+ the type of the left-hand operand
+ </entry>
+ </row>
+
+ <row>
+ <entry>oprrsortop</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_operator.oid</entry>
+ <entry>
+ If this operator supports merge joins, the operator that sorts
+ the type of the left-hand operand
+ </entry>
+ </row>
+
+ <row>
+ <entry>oprcode</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>Function that implements this operator</entry>
+ </row>
+
+ <row>
+ <entry>oprrest</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>Restriction selectivity estimation function for this operator</entry>
+ </row>
+
+ <row>
+ <entry>oprjoin</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>Join selectivity estimation function for this operator</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-proc">
+ <title>pg_proc</title>
+
+ <para>
+ This catalog stores information about functions (or procedures).
+ The description of <command>CREATE FUNCTION</command> and the
+ <citetitle>Programmer's Guide</citetitle> contain more information
+ about the meaning of some fields.
+ </para>
+
+ <table>
+ <title>pg_proc Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>proname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Name of the function</entry>
+ </row>
+
+ <row>
+ <entry>proowner</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner (creator) of the function</entry>
+ </row>
+
+ <row>
+ <entry>prolang</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_language.oid</entry>
+ <entry>Implementation language or call interface of this function</entry>
+ </row>
+
+ <row>
+ <entry>proisinh</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>proistrusted</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>not functional</entry>
+ </row>
+
+ <row>
+ <entry>proiscachable</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>Function returns same result for same input values</entry>
+ </row>
+
+ <row>
+ <entry>proisstrict</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ Function returns null if any call argument is null. In that
+ case the function won't actually be called at all. Functions
+ that are not <quote>strict</quote> must be prepared to handle
+ null inputs.
+ </entry>
+ </row>
+
+ <row>
+ <entry>pronargs</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>Number of arguments</entry>
+ </row>
+
+ <row>
+ <entry>proretset</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>Function returns a set (probably not functional)</entry>
+ </row>
+
+ <row>
+ <entry>prorettype</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>Data type of the return value (0 if the function does not return a value)</entry>
+ </row>
+
+ <row>
+ <entry>proargtypes</entry>
+ <entry><type>oidvector</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>A vector with the data types of the function arguments</entry>
+ </row>
+
+ <row>
+ <entry>probyte_pct</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>dead code</entry>
+ </row>
+
+ <row>
+ <entry>properbyte_pct</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>dead code</entry>
+ </row>
+
+ <row>
+ <entry>propercall_pct</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>dead code</entry>
+ </row>
+
+ <row>
+ <entry>prooutin_ratio</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>dead code</entry>
+ </row>
+
+ <row>
+ <entry>prosrc</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>
+ This tells the function handler how to invoke the function. It
+ might be the actual source code of the function for interpreted
+ languages, a link symbol, a file name, or just about anything
+ else, depending the implementation language/call convention.
+ </entry>
+ </row>
+
+ <row>
+ <entry>probin</entry>
+ <entry><type>bytea</type></entry>
+ <entry></entry>
+ <entry>?</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-relcheck">
+ <title>pg_relcheck</title>
+
+ <para>
+ This system catalog stores CHECK constraints on tables. (Column
+ constraints are not treated specially. Every column constraint is
+ equivalent to some table constraint.) See under <command>CREATE
+ TABLE</command> for more information.
+ </para>
+
+ <table>
+ <title>pg_relcheck Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>rcrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>The table this check constraint is on</entry>
+ </row>
+
+ <row>
+ <entry>rcname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Constraint name</entry>
+ </row>
+
+ <row>
+ <entry>rcbin</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>An internal representation of the constraint expression</entry>
+ </row>
+
+ <row>
+ <entry>rcsrc</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>A human-readable representation of the consraint expression</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <note>
+ <para>
+ <structname>pg_class</structname>.<structfield>relchecks</structfield>
+ needs to match up with the entries in this table.
+ </para>
+ </note>
+
+ </section>
+
+
+ <section id="catalog-pg-shadow">
+ <title>pg_shadow</title>
+
+ <para>
+ <structname>pg_shadow</structname> contains information about
+ database users. The name stems from the fact that this table
+ should not be readable by the public since it contains passwords.
+ <structname>pg_user</structname> is a view on
+ <structname>pg_shadow</structname> that blanks out the password field.
+ </para>
+
+ <para>
+ The <citetitle>Administrator's Guide</citetitle> contains detailed
+ information about user and permission management.
+ </para>
+
+ <table>
+ <title>pg_shadow Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>usename</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>User name</entry>
+ </row>
+
+ <row>
+ <entry>usesysid</entry>
+ <entry><type>int4</type></entry>
+ <entry></entry>
+ <entry>User id (arbitrary number used to reference this user)</entry>
+ </row>
+
+ <row>
+ <entry>usecreatedb</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>User may create databases</entry>
+ </row>
+
+ <row>
+ <entry>usetrace</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>not used</entry>
+ </row>
+
+ <row>
+ <entry>usesuper</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>User is a superuser</entry>
+ </row>
+
+ <row>
+ <entry>usecatupd</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ User may update system catalogs. (Even a superuser may not do
+ this unless this attribute is true.)
+ </entry>
+ </row>
+
+ <row>
+ <entry>passwd</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>Password</entry>
+ </row>
+
+ <row>
+ <entry>valuntil</entry>
+ <entry><type>abstime</type></entry>
+ <entry></entry>
+ <entry>Account expiry time (only used for password authentication)</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+ <section id="catalog-pg-type">
+ <title>pg_type</title>
+
+ <table>
+ <title>pg_type Columns</title>
+
+ <tgroup cols=4>
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Type</entry>
+ <entry>References</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry>typname</entry>
+ <entry><type>name</type></entry>
+ <entry></entry>
+ <entry>Data type name</entry>
+ </row>
+
+ <row>
+ <entry>typowner</entry>
+ <entry><type>int4</type></entry>
+ <entry>pg_shadow.usesysid</entry>
+ <entry>Owner (creator) of the type</entry>
+ </row>
+
+ <row>
+ <entry>typlen</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>Length of the storage representation of the type, -1 if variable length</entry>
+ </row>
+
+ <row>
+ <entry>typprtlen</entry>
+ <entry><type>int2</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>typbyval</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>
+ <structfield>typbyval</structfield> determines whether internal
+ routines pass a value of this type by value or by reference.
+ Only <type>char</type>, <type>short</type>, and
+ <type>int</type> equivalent items can be passed by value, so if
+ the type is not 1, 2, or 4 bytes long, Postgres does not have
+ the option of passing by value and so
+ <structfield>typbyval</structfield> had better be false.
+ Variable-length types are always passed by reference. Note that
+ <structfield>typbyval</structfield> can be false even if the
+ length would allow pass-by-value; this is currently true for
+ type <type>float4</type>, for example.
+ </entry>
+ </row>
+
+ <row>
+ <entry>typtype</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>
+ <structfield>typtype</structfield> is <literal>b</literal> for
+ a basic type and <literal>c</literal> for a catalog type (i.e.,
+ a table). If <structfield>typtype</structfield> is
+ <literal>c</literal>, <structfield>typrelid</structfield> is
+ the OID of the type's entry in
+ <structname>pg_class</structname>.
+ </entry>
+ </row>
+
+ <row>
+ <entry>typisdefined</entry>
+ <entry><type>bool</type></entry>
+ <entry></entry>
+ <entry>???</entry>
+ </row>
+
+ <row>
+ <entry>typdelim</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry>Character that separates two values of this type when parsing array input</entry>
+ </row>
+
+ <row>
+ <entry>typrelid</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_class.oid</entry>
+ <entry>
+ If this is a catalog type (see
+ <structfield>typtype</structfield>), then this field points to
+ the <structfield>pg_class</structfield> entry that defines the
+ corresponding table. A table could theoretically be used as a
+ composite data type, but this is not fully functional.
+ </entry>
+ </row>
+
+ <row>
+ <entry>typelem</entry>
+ <entry><type>oid</type></entry>
+ <entry>pg_type.oid</entry>
+ <entry>
+ If <structfield>typelem</structfield> is not 0 then it
+ identifies another row in <structname>pg_type</structname>.
+ The current type can then be subscripted like an array yielding
+ values of type <structfield>typelem</structfield>. A non-zero
+ <structfield>typelem</structfield> does not guarantee this type
+ to be a <quote>real</quote> array type; some ordinary
+ fixed-length types can also be subscripted (e.g.,
+ <type>oidvector</type>). Variable-length types can
+ <emphasis>not</emphasis> be turned into pseudo-arrays like
+ that. Hence, the way to determine whether a type is a
+ <quote>true</quote> array type is typelem != 0 and typlen < 0.
+ </entry>
+ </row>
+
+ <row>
+ <entry>typinput</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>Input function</entry>
+ </row>
+
+ <row>
+ <entry>typoutput</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>Output function</entry>
+ </row>
+
+ <row>
+ <entry>typreceive</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>typsend</entry>
+ <entry><type>regproc</type></entry>
+ <entry></entry>
+ <entry>unused</entry>
+ </row>
+
+ <row>
+ <entry>typalign</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry><para>
+
+ <structfield>typalign</structfield> is the alignment required
+ when storing a value of this type. It applies to storage on
+ disk as well as most representations of the value inside
+ Postgres. When multiple values are stored consecutively, such
+ as in the representation of a complete row on disk, padding is
+ inserted before a datum of this type so that it begins on the
+ specified boundary. The alignment reference is the beginning
+ of the first datum in the sequence.
+ </para><para>
+ Possible values are:
+ <itemizedlist>
+ <listitem>
+ <para>'c' = CHAR alignment, ie no alignment needed.</para>
+ </listitem>
+ <listitem>
+ <para>'s' = SHORT alignment (2 bytes on most machines).</para>
+ </listitem>
+ <listitem>
+ <para>'i' = INT alignment (4 bytes on most machines).</para>
+ </listitem>
+ <listitem>
+ <para>'d' = DOUBLE alignment (8 bytes on many machines, but by no means all).</para>
+ </listitem>
+ </itemizedlist>
+ </para><note>
+ <para>
+ For types used in system tables, it is critical that the size
+ and alignment defined in <structname>pg_type</structname>
+ agree with the way that the compiler will lay out the field in
+ a struct representing a table row.
+ </para>
+ </note></entry>
+ </row>
+
+ <row>
+ <entry>typstorage</entry>
+ <entry><type>char</type></entry>
+ <entry></entry>
+ <entry><para>
+ <structfield>typstorage</structfield> tells for variable-length
+ types (those with <structfield>typlen</structfield> = -1) if
+ the type is prepared for toasting and what the default strategy
+ for attributes of this type should be.
+ Possible values are
+ <itemizedlist>
+ <listitem>
+ <para>'p': Value must always be stored plain.</para>
+ </listitem>
+ <listitem>
+ <para>
+ 'e': Value can be stored in a <quote>secondary</quote>
+ relation (if relation has one, see
+ <structname>pg_class</structname>.<structfield>reltoastrelid</structfield>).
+ </para>
+ </listitem>
+ <listitem>
+ <para>'m': Value can be stored compressed inline.</para>
+ </listitem>
+ <listitem>
+ <para>'x': Value can be stored compressed inline or in <quote>secondary</quote>.</para>
+ </listitem>
+ </itemizedlist>
+ Note that 'm' fields can also be moved out to secondary
+ storage, but only as a last resort ('e' and 'x' fields are
+ moved first).
+ </para></entry>
+ </row>
+
+ <row>
+ <entry>typdefault</entry>
+ <entry><type>text</type></entry>
+ <entry></entry>
+ <entry>???</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+</chapter>
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