From 60ecd1297355a11df3cddea21eaab5ef6b18de1d Mon Sep 17 00:00:00 2001 From: Chengpeng Yan <41809508+Reminiscent@users.noreply.github.com> Date: Fri, 16 Sep 2022 10:45:24 +0800 Subject: [PATCH] doc: update the doc for hash_join_build and hash_join_probe hints (#11276) * doc: update the doc for hash_join_build and hash_join_probe hints * Update optimizer-hints.md Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com> * Update optimizer-hints.md Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com> * Update optimizer-hints.md Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com> Co-authored-by: Yuanjia Zhang Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com> --- optimizer-hints.md | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/optimizer-hints.md b/optimizer-hints.md index 8c0683e07962..ff709917b105 100644 --- a/optimizer-hints.md +++ b/optimizer-hints.md @@ -125,6 +125,22 @@ SELECT /*+ HASH_JOIN(t1, t2) */ * FROM t1, t2 WHERE t1.id = t2.id; > > `HASH_JOIN` 的别名是 `TIDB_HJ`，在 3.0.x 及之前版本仅支持使用该别名；之后的版本同时支持使用这两种名称，推荐使用 `HASH_JOIN`。 +### HASH_JOIN_BUILD(t1_name [, tl_name ...]) + +`HASH_JOIN_BUILD(t1_name [, tl_name ...])` 提示优化器对指定表使用 Hash Join 算法，同时将指定表作为 Hash Join 算法的 Build 端，即用指定表来构建哈希表。例如： + +```sql +SELECT /*+ HASH_JOIN_BUILD(t1) */ * FROM t1, t2 WHERE t1.id = t2.id; +``` + +### HASH_JOIN_PROBE(t1_name [, tl_name ...]) + +`HASH_JOIN_PROBE(t1_name [, tl_name ...])` 提示优化器对指定表使用 Hash Join 算法，同时将指定表作为 Hash Join 算法的探测（Probe）端，即用指定表作为探测端来执行 Hash Join 算法。例如： + +```sql +SELECT /*+ HASH_JOIN_PROBE(t2) */ * FROM t1, t2 WHERE t1.id = t2.id; +``` + ### SEMI_JOIN_REWRITE() `SEMI_JOIN_REWRITE()` 提示优化器将查询语句中的半连接 (Semi Join) 改写为普通的内连接。目前该 Hint 只作用于 `EXISTS` 子查询。