<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >pg_constraint</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.5 Documentation" HREF="index.html"><LINK REL="UP" TITLE="System Catalogs" HREF="catalogs.html"><LINK REL="PREVIOUS" TITLE="pg_class" HREF="catalog-pg-class.html"><LINK REL="NEXT" TITLE="pg_collation" HREF="catalog-pg-collation.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2013-10-08T03:47:12"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.5 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="pg_class" HREF="catalog-pg-class.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="catalogs.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 45. System Catalogs</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="pg_collation" HREF="catalog-pg-collation.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="CATALOG-PG-CONSTRAINT" >45.12. <TT CLASS="STRUCTNAME" >pg_constraint</TT ></A ></H1 ><P > The catalog <TT CLASS="STRUCTNAME" >pg_constraint</TT > stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the <TT CLASS="STRUCTNAME" >pg_attribute</TT > catalog, not here. </P ><P > User-defined constraint triggers (created with <TT CLASS="COMMAND" >CREATE CONSTRAINT TRIGGER</TT >) also give rise to an entry in this table. </P ><P > Check constraints on domains are stored here, too. </P ><DIV CLASS="TABLE" ><A NAME="AEN89311" ></A ><P ><B >Table 45-12. <TT CLASS="STRUCTNAME" >pg_constraint</TT > Columns</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >References</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="STRUCTFIELD" >conname</TT ></TD ><TD ><TT CLASS="TYPE" >name</TT ></TD ><TD > </TD ><TD >Constraint name (not necessarily unique!)</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >connamespace</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-namespace.html" ><TT CLASS="STRUCTNAME" >pg_namespace</TT ></A >.oid</TT ></TD ><TD > The OID of the namespace that contains this constraint </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >contype</TT ></TD ><TD ><TT CLASS="TYPE" >char</TT ></TD ><TD > </TD ><TD > <TT CLASS="LITERAL" >c</TT > = check constraint, <TT CLASS="LITERAL" >f</TT > = foreign key constraint, <TT CLASS="LITERAL" >p</TT > = primary key constraint, <TT CLASS="LITERAL" >u</TT > = unique constraint, <TT CLASS="LITERAL" >t</TT > = constraint trigger, <TT CLASS="LITERAL" >x</TT > = exclusion constraint </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >condeferrable</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > </TD ><TD >Is the constraint deferrable?</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >condeferred</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > </TD ><TD >Is the constraint deferred by default?</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >convalidated</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > </TD ><TD >Has the constraint been validated? Currently, can only be false for foreign keys and CHECK constraints</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conrelid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-class.html" ><TT CLASS="STRUCTNAME" >pg_class</TT ></A >.oid</TT ></TD ><TD >The table this constraint is on; 0 if not a table constraint</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >contypid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-type.html" ><TT CLASS="STRUCTNAME" >pg_type</TT ></A >.oid</TT ></TD ><TD >The domain this constraint is on; 0 if not a domain constraint</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conindid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-class.html" ><TT CLASS="STRUCTNAME" >pg_class</TT ></A >.oid</TT ></TD ><TD >The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else 0</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >confrelid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-class.html" ><TT CLASS="STRUCTNAME" >pg_class</TT ></A >.oid</TT ></TD ><TD >If a foreign key, the referenced table; else 0</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >confupdtype</TT ></TD ><TD ><TT CLASS="TYPE" >char</TT ></TD ><TD > </TD ><TD >Foreign key update action code: <TT CLASS="LITERAL" >a</TT > = no action, <TT CLASS="LITERAL" >r</TT > = restrict, <TT CLASS="LITERAL" >c</TT > = cascade, <TT CLASS="LITERAL" >n</TT > = set null, <TT CLASS="LITERAL" >d</TT > = set default </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >confdeltype</TT ></TD ><TD ><TT CLASS="TYPE" >char</TT ></TD ><TD > </TD ><TD >Foreign key deletion action code: <TT CLASS="LITERAL" >a</TT > = no action, <TT CLASS="LITERAL" >r</TT > = restrict, <TT CLASS="LITERAL" >c</TT > = cascade, <TT CLASS="LITERAL" >n</TT > = set null, <TT CLASS="LITERAL" >d</TT > = set default </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >confmatchtype</TT ></TD ><TD ><TT CLASS="TYPE" >char</TT ></TD ><TD > </TD ><TD >Foreign key match type: <TT CLASS="LITERAL" >f</TT > = full, <TT CLASS="LITERAL" >p</TT > = partial, <TT CLASS="LITERAL" >u</TT > = simple (unspecified) </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conislocal</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > </TD ><TD > This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously. </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >coninhcount</TT ></TD ><TD ><TT CLASS="TYPE" >int4</TT ></TD ><TD > </TD ><TD > The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed. </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >connoinherit</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > </TD ><TD > This constraint is defined locally for the relation. It is a non-inheritable constraint. </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conkey</TT ></TD ><TD ><TT CLASS="TYPE" >int2[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-attribute.html" ><TT CLASS="STRUCTNAME" >pg_attribute</TT ></A >.attnum</TT ></TD ><TD >If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >confkey</TT ></TD ><TD ><TT CLASS="TYPE" >int2[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-attribute.html" ><TT CLASS="STRUCTNAME" >pg_attribute</TT ></A >.attnum</TT ></TD ><TD >If a foreign key, list of the referenced columns</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conpfeqop</TT ></TD ><TD ><TT CLASS="TYPE" >oid[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-operator.html" ><TT CLASS="STRUCTNAME" >pg_operator</TT ></A >.oid</TT ></TD ><TD >If a foreign key, list of the equality operators for PK = FK comparisons</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conppeqop</TT ></TD ><TD ><TT CLASS="TYPE" >oid[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-operator.html" ><TT CLASS="STRUCTNAME" >pg_operator</TT ></A >.oid</TT ></TD ><TD >If a foreign key, list of the equality operators for PK = PK comparisons</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conffeqop</TT ></TD ><TD ><TT CLASS="TYPE" >oid[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-operator.html" ><TT CLASS="STRUCTNAME" >pg_operator</TT ></A >.oid</TT ></TD ><TD >If a foreign key, list of the equality operators for FK = FK comparisons</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conexclop</TT ></TD ><TD ><TT CLASS="TYPE" >oid[]</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-operator.html" ><TT CLASS="STRUCTNAME" >pg_operator</TT ></A >.oid</TT ></TD ><TD >If an exclusion constraint, list of the per-column exclusion operators</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >conbin</TT ></TD ><TD ><TT CLASS="TYPE" >pg_node_tree</TT ></TD ><TD > </TD ><TD >If a check constraint, an internal representation of the expression</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >consrc</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > </TD ><TD >If a check constraint, a human-readable representation of the expression</TD ></TR ></TBODY ></TABLE ></DIV ><P > In the case of an exclusion constraint, <TT CLASS="STRUCTFIELD" >conkey</TT > is only useful for constraint elements that are simple column references. For other cases, a zero appears in <TT CLASS="STRUCTFIELD" >conkey</TT > and the associated index must be consulted to discover the expression that is constrained. (<TT CLASS="STRUCTFIELD" >conkey</TT > thus has the same contents as <TT CLASS="STRUCTNAME" >pg_index</TT >.<TT CLASS="STRUCTFIELD" >indkey</TT > for the index.) </P ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B > <TT CLASS="STRUCTFIELD" >consrc</TT > is not updated when referenced objects change; for example, it won't track renaming of columns. Rather than relying on this field, it's best to use <CODE CLASS="FUNCTION" >pg_get_constraintdef()</CODE > to extract the definition of a check constraint. </P ></BLOCKQUOTE ></DIV ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B > <TT CLASS="LITERAL" >pg_class.relchecks</TT > needs to agree with the number of check-constraint entries found in this table for each relation. </P ></BLOCKQUOTE ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="catalog-pg-class.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="catalog-pg-collation.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><TT CLASS="STRUCTNAME" >pg_class</TT ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="catalogs.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><TT CLASS="STRUCTNAME" >pg_collation</TT ></TD ></TR ></TABLE ></DIV ></BODY ></HTML >