diff --git a/src/sql/rewrite/ob_transform_simplify_set.cpp b/src/sql/rewrite/ob_transform_simplify_set.cpp index d59796cc82c9ee2364b0f85890afdd7372854aed..9c369a7e62817dfdea740e5d5737f1b0dc99764a 100644 --- a/src/sql/rewrite/ob_transform_simplify_set.cpp +++ b/src/sql/rewrite/ob_transform_simplify_set.cpp @@ -190,46 +190,57 @@ int ObTransformSimplifySet::add_order_by(ObSelectStmt *stmt, ObSelectStmt *upper return ret; } -// -// 判断upper_stmt能否下推distinct/order by/limit操作到stmt // 当上层有不带offset的limit且下层没有limit时可以下推limit，distinct(如果上层有的话)， -// 如果上层还有order by， -// 下推order by(下层order by肯定被消除了remove_order_by_for_set) -// 如果上层有order by 且 order by 跟的一个子查询，则不能下压:select * from t1 union select * from t2 order by (select min(c1) from t3) limit 1; -// -int ObTransformSimplifySet::check_can_push(ObSelectStmt *stmt, ObSelectStmt *upper_stmt, bool &can_push) +// 判断 upper_stmt 能否下推 distinct/order by/limit 操作到 stmt +// 如果 upper stmt 有 limit percent 或者仅有 offset，都不下推 +// 如果下层 stmt 有 limit，都不下推 +// 1. 下推 order by +// 如果下层 stmt 有 order by, 不能下推 order by +// 如果 upper stmt 的 order by 跟的一个子查询，不能下推 order by +// e.g. select * from t1 union select * from t2 order by (select min(c1) from t3) limit 1; +// 2. 下推 distinct/limit +// 如果 upper stmt 有 order by 且不能下推，不能下推 disdinct/limit +int ObTransformSimplifySet::check_can_push(ObSelectStmt *stmt, ObSelectStmt *upper_stmt, + bool &need_push_distinct, bool &need_push_orderby, + bool &can_push) { int ret = OB_SUCCESS; can_push = true; + need_push_distinct = false; + need_push_orderby = false; if (OB_ISNULL(stmt) || OB_ISNULL(upper_stmt)) { ret = OB_INVALID_ARGUMENT; LOG_WARN("null pointer passed to add_distinct", K(ret), K(stmt), K(upper_stmt)); } else if (!upper_stmt->has_limit()) { ret = OB_INVALID_ARGUMENT; LOG_WARN("upper_stmt should have limit ", K(ret), K(upper_stmt->has_limit())); - } else if (stmt->has_limit() || stmt->is_contains_assignment()) { - // 下层有limit + } else if (NULL == upper_stmt->get_limit_expr() || + NULL != upper_stmt->get_limit_percent_expr() || + upper_stmt->is_fetch_with_ties()) { can_push = false; - } else if ((0 < upper_stmt->get_order_item_size() && 0 < stmt->get_order_item_size()) - || NULL == upper_stmt->get_limit_expr() - || NULL != upper_stmt->get_limit_percent_expr() - || upper_stmt->is_fetch_with_ties()) { - // 上层有order by且下层有也不能下推 - // 仅有 offset 不进行下推 - // limit percent不能下推, 因为可能生成topn导致结果错误 + } else if (stmt->has_limit() || stmt->is_contains_assignment()) { can_push = false; - } else { - //上层有order by subquery 不能下推 - for (int64_t i = 0; OB_SUCC(ret) && can_push && i < upper_stmt->get_order_item_size(); ++i) { - ObRawExpr *order_expr = upper_stmt->get_order_item(i).expr_; - if (OB_ISNULL(order_expr)) { - ret = OB_ERR_UNEXPECTED; - LOG_WARN("get unexpected null", K(order_expr)); - } else if (order_expr->has_flag(CNT_SUB_QUERY)) { - can_push = false; - } else if (!order_expr->has_flag(CNT_SET_OP)) { - can_push = false; - } else {/*do nothing*/} + } else if (upper_stmt->has_order_by()) { + if (stmt->has_order_by()) { + // 下层有 order by 不能下推 + can_push = false; + } else { + // 上层有 order by subquery 不能下推 + for (int64_t i = 0; OB_SUCC(ret) && can_push && i < upper_stmt->get_order_item_size(); ++i) { + ObRawExpr *order_expr = upper_stmt->get_order_item(i).expr_; + if (OB_ISNULL(order_expr)) { + ret = OB_ERR_UNEXPECTED; + LOG_WARN("get unexpected null", K(order_expr)); + } else if (order_expr->has_flag(CNT_SUB_QUERY)) { + can_push = false; + } else if (!order_expr->has_flag(CNT_SET_OP)) { + can_push = false; + } else {/*do nothing*/} + } + need_push_orderby = can_push; + need_push_distinct = upper_stmt->is_set_distinct() && can_push; } + } else { + need_push_distinct = upper_stmt->is_set_distinct(); } return ret; } @@ -258,22 +269,25 @@ int ObTransformSimplifySet::add_limit_order_distinct_for_union(const common::ObI /*do nothing*/ } else if(select_stmt->has_limit()){ bool can_push = false; + bool need_push_distinct = false; + bool need_push_orderby = false; ObSelectStmt* child_stmt = NULL; ObIArray &child_stmts = select_stmt->get_set_query(); for (int64_t i = 0; OB_SUCC(ret) && i < child_stmts.count(); ++i) { if (OB_ISNULL(child_stmt = child_stmts.at(i))) { ret = OB_ERR_UNEXPECTED; LOG_WARN("unexpected null", K(ret)); - } else if (OB_FAIL(check_can_push(child_stmt, select_stmt, can_push))) { + } else if (OB_FAIL(check_can_push(child_stmt, select_stmt, need_push_distinct, + need_push_orderby, can_push))) { LOG_WARN("Failed to check left stmt", K(ret)); } else if (!can_push) { /*do nothing*/ - } else if (OB_FAIL(add_distinct(child_stmt, select_stmt))) { + } else if (need_push_distinct && OB_FAIL(add_distinct(child_stmt, select_stmt))) { LOG_WARN("Failed to add distinct to left stmt", K(ret)); + } else if (need_push_orderby && OB_FAIL(add_order_by(child_stmt, select_stmt))) { + LOG_WARN("Failed to add order by to left stmt", K(ret)); } else if (OB_FAIL(add_limit(child_stmt, select_stmt))) { LOG_WARN("Failed to add limit to left stmt", K(ret)); - } else if (OB_FAIL(add_order_by(child_stmt, select_stmt))) { - LOG_WARN("Failed to add order by to left stmt", K(ret)); } else { trans_happened = true; } diff --git a/src/sql/rewrite/ob_transform_simplify_set.h b/src/sql/rewrite/ob_transform_simplify_set.h index ce138cf68603785e1938a0914a2a2ef0e8af21cb..0a4f60e512e1996f3bfde869f50bf942a5fa6d76 100644 --- a/src/sql/rewrite/ob_transform_simplify_set.h +++ b/src/sql/rewrite/ob_transform_simplify_set.h @@ -62,7 +62,8 @@ private: int add_distinct(ObSelectStmt *stmt, ObSelectStmt *select_stmt); int add_limit(ObSelectStmt *stmt, ObSelectStmt *select_stmt); int add_order_by(ObSelectStmt *stmt, ObSelectStmt *select_stmt); - int check_can_push(ObSelectStmt *stmt, ObSelectStmt *upper_stmt, bool &can_push); + int check_can_push(ObSelectStmt *stmt, ObSelectStmt *upper_stmt, bool &need_push_distinct, + bool &need_push_orderby, bool &can_push); int pruning_set_query(common::ObIArray &parent_stmts, ObSelectStmt *&stmt,