$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.211 2004/06/25 17:20:21 tgl Exp $

<indexterm zone="functions-misc">

<primary>pg_get_serial_sequence</primary>

</indexterm>

<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>

<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>

#include "catalog/dependency.h"

#include "catalog/pg_depend.h"

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);

/*

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();

}

TableInfo *owning_tab;

/*

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);

#define CATALOG_VERSION_NO 200406251

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");

extern Datum pg_get_userbyid(PG_FUNCTION_ARGS);

extern Datum pg_get_serial_sequence(PG_FUNCTION_ARGS);