Function exprCollation

src/backend/nodes/nodeFuncs.c:781–1003

* exprCollation - * returns the Oid of the collation of the expression's result. * * Note: expression nodes that can invoke functions generally have an * "inputcollid" field, which is what the function should use as collation. * That is the resolved common collation of the node's inputs. It is often * but not always the same as the result collation; in particular, if the * function produ

 * or vice versa, the two are different.
 */
Oid
exprCollation(const Node *expr)
{
	Oid			coll;

	if (!expr)
		return InvalidOid;

	switch (nodeTag(expr))
	{
		case T_Var:
			coll = ((const Var *) expr)->varcollid;
			break;
		case T_Const:
			coll = ((const Const *) expr)->constcollid;
			break;
		case T_Param:
			coll = ((const Param *) expr)->paramcollid;
			break;
		case T_Aggref:
			coll = ((const Aggref *) expr)->aggcollid;
			break;
		case T_GroupingFunc:
			coll = InvalidOid;
			break;
		case T_GroupId:
			coll = InvalidOid;
			break;
		case T_GroupingSetId:
			coll = InvalidOid;
			break;
		case T_WindowFunc:
			coll = ((const WindowFunc *) expr)->wincollid;
			break;
		case T_SubscriptingRef:
			coll = ((const SubscriptingRef *) expr)->refcollid;
			break;
		case T_FuncExpr:
			coll = ((const FuncExpr *) expr)->funccollid;
			break;
		case T_NamedArgExpr:
			coll = exprCollation((Node *) ((const NamedArgExpr *) expr)->arg);
			break;
		case T_OpExpr:
			coll = ((const OpExpr *) expr)->opcollid;
			break;
		case T_DistinctExpr:
			coll = ((const DistinctExpr *) expr)->opcollid;
			break;
		case T_NullIfExpr:
			coll = ((const NullIfExpr *) expr)->opcollid;
			break;
		case T_ScalarArrayOpExpr:
			/* ScalarArrayOpExpr's result is boolean ... */
			coll = InvalidOid;	/* ... so it has no collation */
			break;
		case T_BoolExpr:
			/* BoolExpr's result is boolean ... */