<!--

$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

-->

<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">

<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>

PG_RETURN_NAME(result);

}

pg_get_serial_sequence(PG_FUNCTION_ARGS)

{

text*tablename=PG_GETARG_TEXT_P(0);

text*columnname=PG_GETARG_TEXT_P(1);

RangeVar*tablerv;

OidtableOid;

char*column;

AttrNumberattnum;

OidsequenceId=InvalidOid;

RelationdepRel;

ScanKeyDatakey[3];

SysScanDescscan;

HeapTupletup;

tablerv=makeRangeVarFromNameList(textToQualifiedNameList(tablename,

"pg_get_serial_sequence"));

tableOid=RangeVarGetRelid(tablerv, false);

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)));

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_dependdeprec= (Form_pg_depend)GETSTRUCT(tup);

if (deprec->classid==RelOid_pg_class&&

deprec->deptype==DEPENDENCY_INTERNAL)

{

sequenceId=deprec->objid;

break;

}

}

systable_endscan(scan);

heap_close(depRel,AccessShareLock);

if (OidIsValid(sequenceId))

{

HeapTupleclasstup;

Form_pg_classclasstuple;

char*nspname;

char*result;

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);

nspname=get_namespace_name(classtuple->relnamespace);

if (!nspname)

elog(ERROR,"cache lookup failed for namespace %u",

classtuple->relnamespace);

result=quote_qualified_identifier(nspname,

NameStr(classtuple->relname));

ReleaseSysCache(classtup);

PG_RETURN_TEXT_P(string_to_text(result));

}

PG_RETURN_NULL();

}

if (!schemaOnly)

{

TableInfo*owning_tab;

resetPQExpBuffer(query);

appendPQExpBuffer(query,"SELECT pg_catalog.setval(");

appendStringLiteral(query,fmtId(tbinfo->dobj.name), true);

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,")");

}

appendStringLiteral(query,fmtId(tbinfo->dobj.name), true);

appendPQExpBuffer(query,", %s, %s);\n",

last, (called ?"true" :"false"));

DESCR("constraint description");

DATA(insertOID=1716 (pg_get_exprPGNSPPGUID12fftfs225"25 26"_null_pg_get_expr-_null_ ));

DESCR("deparse an encoded expression");

DATA(insertOID=1665 (pg_get_serial_sequencePGNSPPGUID12fftfs225"25 25"_null_pg_get_serial_sequence-_null_ ));

DESCR("name of sequence for a serial column");

externDatumpg_get_constraintdef(PG_FUNCTION_ARGS);

externDatumpg_get_constraintdef_ext(PG_FUNCTION_ARGS);

externchar*pg_get_constraintdef_string(OidconstraintId);

externDatumpg_get_userbyid(PG_FUNCTION_ARGS);

externDatumpg_get_expr(PG_FUNCTION_ARGS);

externDatumpg_get_expr_ext(PG_FUNCTION_ARGS);

externDatumpg_get_userbyid(PG_FUNCTION_ARGS);

externDatumpg_get_serial_sequence(PG_FUNCTION_ARGS);

externchar*deparse_expression(Node*expr,List*dpcontext,

boolforceprefix,boolshowimplicit);

externList*deparse_context_for(constchar*aliasname,Oidrelid);