Re: TODO Item - Return compressed length of TOAST datatypes

Bruce Momjian wrote:
> + /*
> + * 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 */

[...]

Is this optimization worth the code complexity?

> + 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)));
> + }

elog(ERROR) is usually used for "can't happen" errors; also, the usual
error message in this scenario is "cache lookup failed [...]". Perhaps
better to use get_typlen() here, anyway.

-Neil