Function exec_eval_using_params

src/pl/plpgsql/src/pl_exec.c:8496–8568

* exec_eval_using_params --- evaluate params of USING clause * * The result data structure is created in the stmt_mcontext, and should * be freed by resetting that context. */

 * be freed by resetting that context.
 */
static ParamListInfo
exec_eval_using_params(PLpgSQL_execstate *estate, List *params)
{
	ParamListInfo paramLI;
	int			nargs;
	MemoryContext stmt_mcontext;
	MemoryContext oldcontext;
	int			i;
	ListCell   *lc;

	/* Fast path for no parameters: we can just return NULL */
	if (params == NIL)
		return NULL;

	nargs = list_length(params);
	stmt_mcontext = get_stmt_mcontext(estate);
	oldcontext = MemoryContextSwitchTo(stmt_mcontext);
	paramLI = makeParamList(nargs);
	MemoryContextSwitchTo(oldcontext);

	i = 0;
	foreach(lc, params)
	{
		PLpgSQL_expr *param = (PLpgSQL_expr *) lfirst(lc);
		ParamExternData *prm = &paramLI->params[i];
		int32		ppdtypmod;

		/*
		 * Always mark params as const, since we only use the result with
		 * one-shot plans.
		 */
		prm->pflags = PARAM_FLAG_CONST;

		prm->value = exec_eval_expr(estate, param,
									&prm->isnull,
									&prm->ptype,
									&ppdtypmod);

		oldcontext = MemoryContextSwitchTo(stmt_mcontext);

		if (prm->ptype == UNKNOWNOID)
		{
			/*
			 * Treat 'unknown' parameters as text, since that's what most
			 * people would expect.  The SPI functions can coerce unknown
			 * constants in a more intelligent way, but not unknown Params.
			 * This code also takes care of copying into the right context.
			 * Note we assume 'unknown' has the representation of C-string.
			 */
			prm->ptype = TEXTOID;
			if (!prm->isnull)
				prm->value = CStringGetTextDatum(DatumGetCString(prm->value));
		}
		/* pass-by-ref non null values must be copied into stmt_mcontext */
		else if (!prm->isnull)
		{
			int16		typLen;
			bool		typByVal;