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Implement information_schema.parameters.parameter_default column

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Reviewed-by: Ali Dar <ali.munir.dar@gmail.com>
Reviewed-by: Amit Khandekar <amit.khandekar@enterprisedb.com>
Reviewed-by: Rodolfo Campero <rodolfo.campero@anachronics.com>
This commit is contained in:
Peter Eisentraut
2013-11-26 23:18:58 -05:00
parent 3803ff985c
commit 85ed91ee7d
8 changed files with 160 additions and 4 deletions
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84
src/backend/utils/adt/ruleutils.c
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@ -2266,6 +2266,90 @@ print_function_arguments(StringInfo buf, HeapTuple proctup,
return argsprinted;
}
static bool
is_input_argument(int nth, const char *argmodes)
{
return (!argmodes
|| argmodes[nth] == PROARGMODE_IN
|| argmodes[nth] == PROARGMODE_INOUT
|| argmodes[nth] == PROARGMODE_VARIADIC);
}
/*
* Get textual representation of a function argument's default value. The
* second argument of this function is the argument number among all arguments
* (i.e. proallargtypes, *not* proargtypes), starting with 1, because that's
* how information_schema.sql uses it.
*/
Datum
pg_get_function_arg_default(PG_FUNCTION_ARGS)
{
Oid funcid = PG_GETARG_OID(0);
int32 nth_arg = PG_GETARG_INT32(1);
HeapTuple proctup;
Form_pg_proc proc;
int numargs;
Oid *argtypes;
char **argnames;
char *argmodes;
int i;
List *argdefaults;
Node *node;
char *str;
int nth_inputarg;
Datum proargdefaults;
bool isnull;
int nth_default;
proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
if (!HeapTupleIsValid(proctup))
elog(ERROR, "cache lookup failed for function %u", funcid);
numargs = get_func_arg_info(proctup, &argtypes, &argnames, &argmodes);
if (nth_arg < 1 || nth_arg > numargs || !is_input_argument(nth_arg - 1, argmodes))
{
ReleaseSysCache(proctup);
PG_RETURN_NULL();
}
nth_inputarg = 0;
for (i = 0; i < nth_arg; i++)
if (is_input_argument(i, argmodes))
nth_inputarg++;
proargdefaults = SysCacheGetAttr(PROCOID, proctup,
Anum_pg_proc_proargdefaults,
&isnull);
if (isnull)
{
ReleaseSysCache(proctup);
PG_RETURN_NULL();
}
str = TextDatumGetCString(proargdefaults);
argdefaults = (List *) stringToNode(str);
Assert(IsA(argdefaults, List));
pfree(str);
proc = (Form_pg_proc) GETSTRUCT(proctup);
/* Calculate index into proargdefaults: proargdefaults corresponds to the
* last N input arguments, where N = pronargdefaults. */
nth_default = nth_inputarg - 1 - (proc->pronargs - proc->pronargdefaults);
if (nth_default < 0 || nth_default >= list_length(argdefaults))
{
ReleaseSysCache(proctup);
PG_RETURN_NULL();
}
node = list_nth(argdefaults, nth_default);
str = deparse_expression(node, NIL, false, false);
ReleaseSysCache(proctup);
PG_RETURN_TEXT_P(string_to_text(str));
}
/*
* deparse_expression - General utility for deparsing expressions