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Add pg_column_size() to return storage size of a column, including

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possible compression.

Mark Kirkwood
This commit is contained in:
Bruce Momjian
2005-07-06 19:02:54 +00:00
parent b9cb132648
commit a923602855
6 changed files with 114 additions and 6 deletions
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47
src/backend/utils/adt/varlena.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.124 2005/07/04 18:56:44 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.125 2005/07/06 19:02:52 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -28,6 +28,7 @@
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
#include "utils/syscache.h"
typedef struct varlena unknown;
@ -2348,3 +2349,47 @@ md5_bytea(PG_FUNCTION_ARGS)
result_text = PG_STR_GET_TEXT(hexsum);
PG_RETURN_TEXT_P(result_text);
}
/*
* Return the length of a datum, possibly compressed
*/
Datum
pg_column_size(PG_FUNCTION_ARGS)
{
Datum value = PG_GETARG_DATUM(0);
int result;
/* fn_extra stores the fixed column length, or -1 for varlena. */
if (fcinfo->flinfo->fn_extra == NULL) /* first call? */
{
/* On the first call lookup the datatype of the supplied argument */
Oid argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0);
HeapTuple tp;
int typlen;
tp = SearchSysCache(TYPEOID,
ObjectIdGetDatum(argtypeid),
0, 0, 0);
if (!HeapTupleIsValid(tp))
{
/* Oid not in pg_type, should never happen. */
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("invalid typid: %u", argtypeid)));
}
typlen = ((Form_pg_type)GETSTRUCT(tp))->typlen;
ReleaseSysCache(tp);
fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
sizeof(int));
*(int *)fcinfo->flinfo->fn_extra = typlen;
}
if (*(int *)fcinfo->flinfo->fn_extra != -1)
PG_RETURN_INT32(*(int *)fcinfo->flinfo->fn_extra);
else
{
result = toast_datum_size(value) - VARHDRSZ;
PG_RETURN_INT32(result);
}
}