Add pg_get_serial_sequence() function, and cause pg_dump to use it.

This eliminates the assumption that a serial column's sequence will
have the same name on reload that it was given in the original database.

Christopher Kings-Lynne

doc/src/sgml/func.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.210 2004/06/24 19:57:14 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.211 2004/06/25 17:20:21 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -7228,29 +7228,13 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
     <primary>pg_get_userbyid</primary>
    </indexterm>
 
+   <indexterm zone="functions-misc">
+    <primary>pg_get_serial_sequence</primary>
+   </indexterm>
+
   <para>
    <xref linkend="functions-misc-catalog-table"> lists functions that
    extract information from the system catalogs.
-   <function>pg_get_viewdef</function>,
-   <function>pg_get_ruledef</function>,
-   <function>pg_get_indexdef</function>,
-   <function>pg_get_triggerdef</function>, and
-   <function>pg_get_constraintdef</function> respectively
-   reconstruct the creating command for a view, rule, index, trigger, or
-   constraint.  (Note that this is a decompiled reconstruction, not
-   the original text of the command.)  Most of these come in two
-   variants, one of which can optionally <quote>pretty-print</> the result.
-   The pretty-printed format is more readable, but the default format is more
-   likely to be
-   interpreted the same way by future versions of <productname>PostgreSQL</>;
-   avoid using pretty-printed output for dump purposes.
-   Passing <literal>false</> for the pretty-print parameter yields the
-   same result as the variant that does not have the parameter at all.
-   <function>pg_get_expr</function> decompiles the internal form of an
-   individual expression, such as the default value for a column.  It
-   may be useful when examining the contents of system catalogs.
-   <function>pg_get_userbyid</function>
-   extracts a user's name given a user ID number.
   </para>
 
    <table id="functions-misc-catalog-table">
@@ -7335,10 +7319,49 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        <entry><type>name</type></entry>
        <entry>get user name with given ID</entry>
       </row>
+      <row>
+       <entry><literal><function>pg_get_serial_sequence</function>(<parameter>table_name</parameter>, <parameter>column_name</parameter>)</literal></entry>
+       <entry><type>text</type></entry>
+       <entry>get name of the sequence that a serial or bigserial column
+       uses</entry>
+      </row>
      </tbody>
     </tgroup>
    </table>
 
+  <para>
+   <function>pg_get_viewdef</function>,
+   <function>pg_get_ruledef</function>,
+   <function>pg_get_indexdef</function>,
+   <function>pg_get_triggerdef</function>, and
+   <function>pg_get_constraintdef</function> respectively
+   reconstruct the creating command for a view, rule, index, trigger, or
+   constraint.  (Note that this is a decompiled reconstruction, not
+   the original text of the command.)
+   <function>pg_get_expr</function> decompiles the internal form of an
+   individual expression, such as the default value for a column.  It
+   may be useful when examining the contents of system catalogs.
+   Most of these functions come in two
+   variants, one of which can optionally <quote>pretty-print</> the result.
+   The pretty-printed format is more readable, but the default format is more
+   likely to be
+   interpreted the same way by future versions of <productname>PostgreSQL</>;
+   avoid using pretty-printed output for dump purposes.
+   Passing <literal>false</> for the pretty-print parameter yields the
+   same result as the variant that does not have the parameter at all.
+  </para>
+
+  <para>
+   <function>pg_get_userbyid</function>
+   extracts a user's name given a user ID number.
+   <function>pg_get_serial_sequence</function>
+   fetches the name of the sequence associated with a serial or
+   bigserial column.  The name is suitably formatted
+   for passing to the sequence functions (see <xref
+   linkend="functions-sequence">).
+   NULL is returned if the column does not have a sequence attached.
+  </para>
+
    <indexterm zone="functions-misc">
     <primary>obj_description</primary>
    </indexterm>

src/backend/utils/adt/ruleutils.c

@@ -3,7 +3,7 @@
  *				back to source text
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.173 2004/06/18 06:13:49 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.174 2004/06/25 17:20:24 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -42,12 +42,14 @@
 
 #include "access/genam.h"
 #include "catalog/catname.h"
+#include "catalog/dependency.h"
 #include "catalog/heap.h"
 #include "catalog/index.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_cast.h"
 #include "catalog/pg_constraint.h"
+#include "catalog/pg_depend.h"
 #include "catalog/pg_index.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
@@ -1232,6 +1234,116 @@ pg_get_userbyid(PG_FUNCTION_ARGS)
 	PG_RETURN_NAME(result);
 }
 
+
+/*
+ * pg_get_serial_sequence
+ *		Get the name of the sequence used by a serial column,
+ *		formatted suitably for passing to setval, nextval or currval.
+ */
+Datum
+pg_get_serial_sequence(PG_FUNCTION_ARGS)
+{
+	text	*tablename = PG_GETARG_TEXT_P(0);
+	text	*columnname = PG_GETARG_TEXT_P(1);
+	RangeVar   *tablerv;
+	Oid			tableOid;
+	char	*column;
+	AttrNumber	attnum;
+	Oid		sequenceId = InvalidOid;
+	Relation	depRel;
+	ScanKeyData key[3];
+	SysScanDesc scan;
+	HeapTuple	tup;
+
+	/* Get the OID of the table */
+	tablerv = makeRangeVarFromNameList(textToQualifiedNameList(tablename,
+													"pg_get_serial_sequence"));
+	tableOid = RangeVarGetRelid(tablerv, false);
+
+	/* Get the number of the column */
+	column = DatumGetCString(DirectFunctionCall1(textout,
+												 PointerGetDatum(columnname)));
+
+	attnum = get_attnum(tableOid, column);
+	if (attnum == InvalidAttrNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_COLUMN),
+				 errmsg("column \"%s\" of relation \"%s\" does not exist",
+						column, tablerv->relname)));
+
+	/* Search the dependency table for the dependent sequence */
+	depRel = heap_openr(DependRelationName, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_depend_refclassid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(RelOid_pg_class));
+	ScanKeyInit(&key[1],
+				Anum_pg_depend_refobjid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(tableOid));
+	ScanKeyInit(&key[2],
+				Anum_pg_depend_refobjsubid,
+				BTEqualStrategyNumber, F_INT4EQ,
+				Int32GetDatum(attnum));
+
+	scan = systable_beginscan(depRel, DependReferenceIndex, true,
+							  SnapshotNow, 3, key);
+
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_depend	deprec = (Form_pg_depend) GETSTRUCT(tup);
+
+		/*
+		 * We assume any internal dependency of a relation on a column
+		 * must be what we are looking for.
+		 */
+		if (deprec->classid == RelOid_pg_class &&
+			deprec->objsubid == 0 &&
+			deprec->deptype == DEPENDENCY_INTERNAL)
+		{
+			sequenceId = deprec->objid;
+			break;
+		}
+	}
+
+	systable_endscan(scan);
+	heap_close(depRel, AccessShareLock);
+
+	if (OidIsValid(sequenceId))
+	{
+		HeapTuple	classtup;
+		Form_pg_class	classtuple;
+		char *nspname;
+		char *result;
+
+		/* Get the sequence's pg_class entry */
+		classtup = SearchSysCache(RELOID,
+								  ObjectIdGetDatum(sequenceId),
+								  0, 0, 0);
+		if (!HeapTupleIsValid(classtup))
+			elog(ERROR, "cache lookup failed for relation %u", sequenceId);
+		classtuple = (Form_pg_class) GETSTRUCT(classtup);
+
+		/* Get the namespace */
+		nspname = get_namespace_name(classtuple->relnamespace);
+		if (!nspname)
+			elog(ERROR, "cache lookup failed for namespace %u",
+				 classtuple->relnamespace);
+
+		/* And construct the result string */
+		result = quote_qualified_identifier(nspname,
+											NameStr(classtuple->relname));
+
+		ReleaseSysCache(classtup);
+
+		PG_RETURN_TEXT_P(string_to_text(result));
+	}
+
+	PG_RETURN_NULL();
+}
+
+
 /* ----------
  * deparse_expression			- General utility for deparsing expressions
  *

src/bin/pg_dump/pg_dump.c

@@ -12,7 +12,7 @@
  *	by PostgreSQL
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.376 2004/06/21 13:36:41 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.377 2004/06/25 17:20:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -7319,9 +7319,27 @@ dumpSequence(Archive *fout, TableInfo *tbinfo)
 
 	if (!schemaOnly)
 	{
+		TableInfo	*owning_tab;
+
 		resetPQExpBuffer(query);
 		appendPQExpBuffer(query, "SELECT pg_catalog.setval(");
-		appendStringLiteral(query, fmtId(tbinfo->dobj.name), true);
+		/*
+		 * If this is a SERIAL sequence, then use the pg_get_serial_sequence
+		 * function to avoid hard-coding the sequence name.  Note that this
+		 * implicitly assumes that the sequence and its owning table are in
+		 * the same schema, because we don't schema-qualify the reference.
+		 */
+		if (OidIsValid(tbinfo->owning_tab) &&
+			(owning_tab = findTableByOid(tbinfo->owning_tab)) != NULL)
+		{
+			appendPQExpBuffer(query, "pg_catalog.pg_get_serial_sequence(");
+			appendStringLiteral(query, fmtId(owning_tab->dobj.name), true);
+			appendPQExpBuffer(query, ", ");
+			appendStringLiteral(query, owning_tab->attnames[tbinfo->owning_col-1], true);
+			appendPQExpBuffer(query, ")");
+		}
+		else
+			appendStringLiteral(query, fmtId(tbinfo->dobj.name), true);
 		appendPQExpBuffer(query, ", %s, %s);\n",
 						  last, (called ? "true" : "false"));
 

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.239 2004/06/21 04:06:07 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.240 2004/06/25 17:20:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200406202
+#define CATALOG_VERSION_NO	200406251
 
 #endif

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.338 2004/06/16 01:26:49 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.339 2004/06/25 17:20:28 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -2238,6 +2238,8 @@ DATA(insert OID = 1387 (  pg_get_constraintdef PGNSP PGUID 12 f f t f s 1 25 "26
 DESCR("constraint description");
 DATA(insert OID = 1716 (  pg_get_expr		   PGNSP PGUID 12 f f t f s 2 25 "25 26" _null_	pg_get_expr - _null_ ));
 DESCR("deparse an encoded expression");
+DATA(insert OID = 1665 (  pg_get_serial_sequence	PGNSP PGUID 12 f f t f s 2 25 "25 25" _null_  pg_get_serial_sequence - _null_ ));
+DESCR("name of sequence for a serial column");
 
 
 /* Generic referential integrity constraint triggers */

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.243 2004/06/13 21:57:26 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.244 2004/06/25 17:20:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -472,9 +472,10 @@ extern Datum pg_get_triggerdef(PG_FUNCTION_ARGS);
 extern Datum pg_get_constraintdef(PG_FUNCTION_ARGS);
 extern Datum pg_get_constraintdef_ext(PG_FUNCTION_ARGS);
 extern char *pg_get_constraintdef_string(Oid constraintId);
-extern Datum pg_get_userbyid(PG_FUNCTION_ARGS);
 extern Datum pg_get_expr(PG_FUNCTION_ARGS);
 extern Datum pg_get_expr_ext(PG_FUNCTION_ARGS);
+extern Datum pg_get_userbyid(PG_FUNCTION_ARGS);
+extern Datum pg_get_serial_sequence(PG_FUNCTION_ARGS);
 extern char *deparse_expression(Node *expr, List *dpcontext,
 				   bool forceprefix, bool showimplicit);
 extern List *deparse_context_for(const char *aliasname, Oid relid);