Function exec_assign_value

src/pl/plpgsql/src/pl_exec.c:5010–5218

---------- * exec_assign_value Put a value into a target datum * * Note: in some code paths, this will leak memory in the eval_mcontext; * we assume that will be cleaned up later by exec_eval_cleanup. We cannot * call exec_eval_cleanup here for fear of destroying the input Datum value. * ---------- */

 * ----------
 */
static void
exec_assign_value(PLpgSQL_execstate *estate,
				  PLpgSQL_datum *target,
				  Datum value, bool isNull,
				  Oid valtype, int32 valtypmod)
{
	switch (target->dtype)
	{
		case PLPGSQL_DTYPE_VAR:
		case PLPGSQL_DTYPE_PROMISE:
			{
				/*
				 * Target is a variable
				 */
				PLpgSQL_var *var = (PLpgSQL_var *) target;
				Datum		newvalue;

				newvalue = exec_cast_value(estate,
										   value,
										   &isNull,
										   valtype,
										   valtypmod,
										   var->datatype->typoid,
										   var->datatype->atttypmod);

				if (isNull && var->notnull)
					ereport(ERROR,
							(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
							 errmsg("null value cannot be assigned to variable \"%s\" declared NOT NULL",
									var->refname)));

				/*
				 * If type is by-reference, copy the new value (which is
				 * probably in the eval_mcontext) into the procedure's main
				 * memory context.  But if it's a read/write reference to an
				 * expanded object, no physical copy needs to happen; at most
				 * we need to reparent the object's memory context.
				 *
				 * If it's an array, we force the value to be stored in R/W
				 * expanded form.  This wins if the function later does, say,
				 * a lot of array subscripting operations on the variable, and
				 * otherwise might lose.  We might need to use a different
				 * heuristic, but it's too soon to tell.  Also, are there
				 * cases where it'd be useful to force non-array values into
				 * expanded form?
				 */
				if (!var->datatype->typbyval && !isNull)
				{
					if (var->datatype->typisarray &&
						!VARATT_IS_EXTERNAL_EXPANDED_RW(DatumGetPointer(newvalue)))
					{
						/* array and not already R/W, so apply expand_array */
						newvalue = expand_array(newvalue,
												estate->datum_context,
												NULL);
					}
					else
					{