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Add COLLATION FOR expression

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reviewed by Jaime Casanova
This commit is contained in:
Peter Eisentraut
2012-03-02 21:12:16 +02:00
parent d41f510c80
commit 6688d2878e
9 changed files with 103 additions and 3 deletions
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27
src/backend/utils/adt/misc.c
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@ -32,6 +32,7 @@
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/lsyscache.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/timestamp.h"
@ -492,3 +493,29 @@ pg_typeof(PG_FUNCTION_ARGS)
{
PG_RETURN_OID(get_fn_expr_argtype(fcinfo->flinfo, 0));
}
/*
* Implementation of the COLLATE FOR expression; returns the collation
* of the argument.
*/
Datum
pg_collation_for(PG_FUNCTION_ARGS)
{
Oid typeid;
Oid collid;
typeid = get_fn_expr_argtype(fcinfo->flinfo, 0);
if (!typeid)
PG_RETURN_NULL();
if (!type_is_collatable(typeid) && typeid != UNKNOWNOID)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("collations are not supported by type %s",
format_type_be(typeid))));
collid = PG_GET_COLLATION();
if (!collid)
PG_RETURN_NULL();
PG_RETURN_TEXT_P(cstring_to_text(generate_collation_name(collid)));
}