Function splitJoinQualExpr

src/backend/executor/nodeNestloop.c:673–718

---------------------------------------------------------------- * splitJoinQualExpr * * Deconstruct the join clauses into outer and inner argument values, so * that we can evaluate those subexpressions separately. Note: for constant * expression we don't need to split (MPP-21294). However, if constant expressions * have peer splittable expressions we *do* split those. * * This is used for

 * ----------------------------------------------------------------
 */
static void
splitJoinQualExpr(List *joinqual, List **inner_join_keys_p, List **outer_join_keys_p)
{
	List *lclauses = NIL;
	List *rclauses = NIL;
	ListCell   *lc;

	foreach(lc, joinqual)
	{
		Expr	   *expr = (Expr *) lfirst(lc);

		switch (expr->type)
		{
			case T_FuncExpr:
			case T_OpExpr:
				extractFuncExprArgs(expr, &lclauses, &rclauses);
				break;

			case T_BoolExpr:
				{
					BoolExpr   *bexpr = (BoolExpr *) expr;
					ListCell   *argslc;

					foreach(argslc, bexpr->args)
					{
						extractFuncExprArgs(lfirst(argslc), &lclauses, &rclauses);
					}
				}
				break;

			case T_Const:
				/*
				 * Constant expressions do not need to be splitted into left and
				 * right as they don't need to be considered for NULL value special
				 * cases
				 */
				break;

			default:
				elog(ERROR, "unexpected expression type in NestLoopJoin qual");
		}
	}

	*inner_join_keys_p = rclauses;
	*outer_join_keys_p = lclauses;
}


/* ----------------------------------------------------------------