{"id":3737,"date":"2021-01-25T14:20:49","date_gmt":"2021-01-25T06:20:49","guid":{"rendered":"https:\/\/www.gbase8.cn\/?p=3737"},"modified":"2021-01-25T15:48:19","modified_gmt":"2021-01-25T07:48:19","slug":"gbase-8a%e5%81%9adistinct%e6%93%8d%e4%bd%9c%e5%8f%91%e7%94%9f%e5%8a%a8%e6%80%81hash%e9%87%8d%e5%88%86%e5%b8%83%e6%97%b6%e6%8c%87%e5%ae%9a%e5%a4%9a%e4%b8%aa%e5%88%97%e9%81%bf%e5%85%8d%e4%b8%a5%e9%87%8d","status":"publish","type":"post","link":"https:\/\/www.gbase8.cn\/en\/3737","title":{"rendered":"\u5357\u5927\u901a\u7528GBase 8a\u505adistinct\u3001group\u548cjoin\u65f6\u907f\u514d\u4e25\u91cd\u6570\u636e\u503e\u659c\u5bfc\u81f4\u7684\u6027\u80fd\u95ee\u9898"},"content":{"rendered":"<p>\u5728\u6267\u884cdistinct\u3001group\u3001join\u662f\u7531\u591a\u4e2a\u5217\u53c2\u6570\u65f6\uff0c\u5982\u679c\u6295\u5f71\u5217\u91cc\u6ca1\u6709Hash\u5206\u5e03\u5217\uff0c\u5219\u4f1a\u9009\u62e9\u4e00\u4e2a\u5217\u505ahash\u52a8\u6001\u91cd\u5206\u5e03\u3002GBase 8a\u6570\u636e\u5e93\u96c6\u7fa4\u901a\u8fc7_t_gcluster_distinct_multi_redist\u548c_t_gcluster_hash_redistribute_groupby_on_multiple_expression\u53c2\u6570\uff0c\u53ef\u4ee5\u6307\u5b9a\u591a\u4e2a\u5217\u53c2\u4e0ehash\u8ba1\u7b97\uff0c\u907f\u514dGBase 8a\u505adistinct\u3001group\u3001join\u65f6\u901a\u8fc7\u6307\u5b9a\u591a\u5217\u52a8\u6001Hash\u91cd\u5206\u5e03\u907f\u514d\u4e25\u91cd\u6570\u636e\u503e\u659c\u5bfc\u81f4\u7684\u6027\u80fd\u95ee\u9898\u3002<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_84 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Directory Navigation<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-6a2b004ef36ad\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" 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href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%B8%B8%E8%A7%81%E4%B8%9A%E5%8A%A1%E5%9C%BA%E6%99%AF%E5%A6%82%E4%B8%8B\" >\u5e38\u89c1\u4e1a\u52a1\u573a\u666f\u5982\u4e0b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E6%8F%90%E9%86%92\" >\u63d0\u9192<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#distinct_%E6%93%8D%E4%BD%9C\" >distinct \u64cd\u4f5c<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0\" >\u53c2\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%AF%B4%E6%98%8E\" >\u8bf4\u660e<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E6%A0%B7%E4%BE%8B\" >\u6837\u4f8b<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%A1%A8%E7%BB%93%E6%9E%84\" >\u8868\u7ed3\u6784<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92\" >\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92\" >\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><\/ul><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#group%E6%93%8D%E4%BD%9C\" >group\u64cd\u4f5c<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0-2\" >\u53c2\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%AF%B4%E6%98%8E-2\" >\u8bf4\u660e<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E6%A0%B7%E4%BE%8B-2\" >\u6837\u4f8b<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%A1%A8%E7%BB%93%E6%9E%84-2\" >\u8868\u7ed3\u6784<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-2\" >\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-2\" >\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><\/ul><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#join_%E6%93%8D%E4%BD%9C\" >join \u64cd\u4f5c<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0-3\" >\u53c2\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%AF%B4%E6%98%8E-3\" >\u8bf4\u660e<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E6%A0%B7%E4%BE%8B-3\" >\u6837\u4f8b<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E8%A1%A8%E7%BB%93%E6%9E%84-3\" >\u8868\u7ed3\u6784<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-3\" >\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-3\" >\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E6%B3%A8%E6%84%8F\" >\u6ce8\u610f<\/a><\/li><\/ul><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-25\" href=\"https:\/\/www.gbase8.cn\/en\/3737\/#%E5%8F%82%E8%80%83\" >\u53c2\u8003<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%B8%B8%E8%A7%81%E4%B8%9A%E5%8A%A1%E5%9C%BA%E6%99%AF%E5%A6%82%E4%B8%8B\"><\/span>\u5e38\u89c1\u4e1a\u52a1\u573a\u666f\u5982\u4e0b<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>select distinct id1,id2,id3... from table\uff0c\nselect id1,id2,count(*) from table group by id1,id2\nselect a.* from a left join b on a.id=b.id and a.id2=b.id2<\/code><\/pre>\n\n\n\n<p>\u5f53\u7136\uff0c\u5982\u679c\u6709hash\u5217\u53c2\u4e0e\uff0c\u6216\u8005\u7b2c\u4e00\u4e2a\u5217\u6ca1\u6709\u6bd4\u8f83\u4e25\u91cd\u7684\u503e\u659c\uff0c\u90a3\u4e48\u8fd9\u4e2a\u53c2\u6570\u5c31\u4e0d\u8981\u7528\u4e86\u3002\u6ce8\u610f\u503e\u659c\u7684\u5b9a\u4e49\uff0c\u53ef\u4ee5\u53c2\u8003\u6267\u884c\u65f6\u95f4\uff0c\u5982\u679c\u6bcf\u6b21\u90fd\u662f\u5176\u5b83\u8282\u70b9\u5f88\u5feb\u7ed3\u675f\uff0c\u67d0\u4e00\u4e2a\u6216\u51e0\u4e2a\u8282\u70b9\u8017\u65f6\u957f\uff0c\u6bd4\u5982\u8d85\u8fc730%\u3002 \u67e5\u770bgnode\u8ba1\u7b97\u8282\u70b9\u4e0asql\u7684\u65b9\u6cd5\uff0c\u8bf7\u53c2\u8003 <a href=\"https:\/\/www.gbase8.cn\/en\/657\/\">GBase 8a\u6570\u636e\u5e93\u96c6\u7fa4\u8fd0\u7ef4\u5de1\u68c0\u7ef4\u62a4\u5e38\u7528\u547d\u4ee4\u7b80\u5316\u7248<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%8F%90%E9%86%92\"><\/span>\u63d0\u9192<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u672c\u6587\u4ecb\u7ecd\u76842\u4e2a\u53c2\u6570\uff0c\u90fd\u662f\u4e0b\u5212\u7ebf\u5f00\u5934\u7684\uff0c\u4ee3\u8868\u53c2\u6570\u5e76\u6ca1\u6709\u6b63\u5f0f\u5bf9\u5916\u5f00\u653e\u4f7f\u7528\uff0c\u4e5f\u4e0d\u4fdd\u8bc1\u65b0\u7248\u672c\u8fd8\u4f1a\u4fdd\u7559\uff0c\u5c31\u7b97\u4fdd\u7559\u4e5f\u4e0d\u786e\u4fdd\u662f\u76f8\u540c\u7684\u540d\u5b57\u3002\u6240\u4ee5\u5982\u679c\u5728\u67d0\u4e2a\u7248\u672c\u53ef\u7528\uff0c\u540e\u7eed\u5347\u7ea7\u65f6\u8bf7\u54a8\u8be2\u5382\u5bb6\u83b7\u5f97\u53d8\u52a8\u5217\u8868\u5e76\u8fdb\u884c\u6d4b\u8bd5\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"distinct_%E6%93%8D%E4%BD%9C\"><\/span>distinct \u64cd\u4f5c<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0\"><\/span>\u53c2\u6570<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u9ed8\u8ba4\u503c\u4e3a1\uff0c\u53ef\u9009\u503c\u4e3a1\u548c2\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>_t_gcluster_distinct_multi_redist<\/code><\/pre>\n\n\n\n<p>\u53c2\u6570\u4e3a1\uff0c\u6309\u7167\u5355\u5217\u8ba1\u7b97\u8fdb\u884c\u91cd\u5206\u5e03\u53bb\u91cd<br>\u53c2\u6570\u4e3a2\uff0c\u6309\u7167\u591a\u5217\u8ba1\u7b97\u8fdb\u884c\u91cd\u5206\u5e03\u53bb\u91cd<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%AF%B4%E6%98%8E\"><\/span>\u8bf4\u660e<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u5e38\u91cf\u3001\u6807\u91cf\u5b50\u67e5\u8be2\u4e0d\u4f1a\u4f5c\u4e3a\u91cd\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<p>\u8bbe\u7f6e\u8be5\u53c2\u6570\u4e3a2\uff0c\u7531\u4e8e\u5728hash\u9636\u6bb5\u8ba1\u7b97\u4e86\u591a\u4e2a\u5217\uff0c\u968f\u7740distinct\u5217\u7684\u589e\u591a\uff0c\u8ba1\u7b97\u6210\u672c\u589e\u52a0\uff0c\u65f6\u95f4\u589e\u957f\uff0c\u6240\u4ee5\u8981\u4ee5\u6d4b\u8bd5\u7ed3\u679c\u4e3a\u51c6\uff0c\u5728\u6570\u636e\u503e\u659c\u548c\u6027\u80fd\u4e4b\u95f4\u5e73\u8861\u3002<\/p>\n\n\n\n<p>\u53e6\u5916\uff0cdistinct\uff0cgroup\u7b49\u6709\u591a\u4e2a\u5217\u7684\u573a\u666f\uff0c\u65e0\u8bba\u4ec0\u4e48\u60c5\u51b5\uff0c\u90fd\u5efa\u8bae\u5c06\u552f\u4e00\u503c\u591a\u7684\u653e\u7b2c\u4e00\u4e2a\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%A0%B7%E4%BE%8B\"><\/span>\u6837\u4f8b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A1%A8%E7%BB%93%E6%9E%84\"><\/span>\u8868\u7ed3\u6784<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u5982\u4e0b\u662f\u4e00\u4e2a2\u4e2a\u5217\u7684\u968f\u673a\u5206\u5e03\u8868\uff0c\u6ca1\u6709hash\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; desc t1;\n+-------+--------------+------+-----+---------+-------+\n| Field | Type         | Null | Key | Default | Extra |\n+-------+--------------+------+-----+---------+-------+\n| id    | int(11)      | YES  |     | NULL    |       |\n| name  | varchar(100) | YES  |     | NULL    |       |\n+-------+--------------+------+-----+---------+-------+\n2 rows in set (Elapsed: 00:00:00.00)\n\ngbase&gt; show create table t1;\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| Table | Create Table                                                                                                                                          |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| t1    | CREATE TABLE \"t1\" (\n  \"id\" int(11) DEFAULT NULL,\n  \"name\" varchar(100) DEFAULT NULL\n) ENGINE=EXPRESS DEFAULT CHARSET=utf8 TABLESPACE='sys_tablespace' |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n1 row in set (Elapsed: 00:00:00.00)\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92\"><\/span>\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230REDIST\u91cd\u5206\u5e03\u65f6\uff0c\u7528ID\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; explain select distinct id,name from t1;\n+----+--------------+-----------+---------+-----------+\n| ID | MOTION       | OPERATION | TABLE   | CONDITION |\n+----+--------------+-----------+---------+-----------+\n| 01 | &#91;RESULT]     |  Step     | &lt;00&gt;    |           |\n|    |              |  AGG      |         |           |\n| 00 | &#91;REDIST(id)] |  Table    | t1&#91;DIS] |           |\n|    |              |  AGG      |         |           |\n+----+--------------+-----------+---------+-----------+\n4 rows in set (Elapsed: 00:00:00.00)\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92\"><\/span>\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u4fee\u6539\u53c2\u6570\u7b49\u4e8e2\u540e\uff0c\u91cd\u5206\u5e03REDIST\u91c7\u7528\u4e86id,name\u4e24\u4e2a\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; set _t_gcluster_distinct_multi_redist=2;\nQuery OK, 0 rows affected (Elapsed: 00:00:00.00)\n\ngbase&gt; explain select distinct id,name from t1;\n+----+-------------------+-----------+---------+-----------+\n| ID | MOTION            | OPERATION | TABLE   | CONDITION |\n+----+-------------------+-----------+---------+-----------+\n| 01 | &#91;RESULT]          |  Step     | &lt;00&gt;    |           |\n|    |                   |  AGG      |         |           |\n| 00 | &#91;REDIST(id,name)] |  Table    | t1&#91;DIS] |           |\n|    |                   |  AGG      |         |           |\n+----+-------------------+-----------+---------+-----------+\n4 rows in set (Elapsed: 00:00:00.00)\n<\/code><\/pre>\n\n\n\n<p><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"group%E6%93%8D%E4%BD%9C\"><\/span>group\u64cd\u4f5c<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0-2\"><\/span>\u53c2\u6570<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u9ed8\u8ba4\u503c\u662f0\uff0c\u4f7f\u75281\u4e2a\u5217\u505a\u91cd\u5206\u5e03\u30021\u662f\u7528\u591a\u4e2a\u5217\u505a\u91cd\u5206\u5e03\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>t_gcluster_hash_redistribute_groupby_on_multiple_expression<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%AF%B4%E6%98%8E-2\"><\/span>\u8bf4\u660e<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u5e38\u91cf\u3001\u6807\u91cf\u5b50\u67e5\u8be2\u4e0d\u4f1a\u4f5c\u4e3a\u91cd\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<p>\u8bbe\u7f6e\u8be5\u53c2\u6570\u4e3a1\uff0c\u7531\u4e8e\u5728hash\u9636\u6bb5\u8ba1\u7b97\u4e86\u591a\u4e2a\u5217\uff0c\u968f\u7740group\u5217\u7684\u589e\u591a\uff0c\u8ba1\u7b97\u6210\u672c\u589e\u52a0\uff0c\u65f6\u95f4\u589e\u957f\uff0c\u6240\u4ee5\u8981\u4ee5\u6d4b\u8bd5\u7ed3\u679c\u4e3a\u51c6\uff0c\u5728\u6570\u636e\u503e\u659c\u548c\u6027\u80fd\u4e4b\u95f4\u5e73\u8861\u3002<\/p>\n\n\n\n<p>\u53e6\u5916\uff0cdistinct\uff0cgroup\u7b49\u6709\u591a\u4e2a\u5217\u7684\u573a\u666f\uff0c\u65e0\u8bba\u4ec0\u4e48\u60c5\u51b5\uff0c\u90fd\u5efa\u8bae\u5c06\u552f\u4e00\u503c\u591a\u7684\u653e\u7b2c\u4e00\u4e2a\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%A0%B7%E4%BE%8B-2\"><\/span>\u6837\u4f8b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A1%A8%E7%BB%93%E6%9E%84-2\"><\/span>\u8868\u7ed3\u6784<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u5982\u4e0b\u662f\u4e00\u4e2a2\u4e2a\u5217\u7684\u968f\u673a\u5206\u5e03\u8868\uff0c\u6ca1\u6709hash\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; desc t1;\n+-------+--------------+------+-----+---------+-------+\n| Field | Type         | Null | Key | Default | Extra |\n+-------+--------------+------+-----+---------+-------+\n| id    | int(11)      | YES  |     | NULL    |       |\n| name  | varchar(100) | YES  |     | NULL    |       |\n+-------+--------------+------+-----+---------+-------+\n2 rows in set (Elapsed: 00:00:00.00)\n\ngbase&gt; show create table t1;\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| Table | Create Table                                                                                                                                          |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| t1    | CREATE TABLE \"t1\" (\n  \"id\" int(11) DEFAULT NULL,\n  \"name\" varchar(100) DEFAULT NULL\n) ENGINE=EXPRESS DEFAULT CHARSET=utf8 TABLESPACE='sys_tablespace' |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n1 row in set (Elapsed: 00:00:00.00)\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-2\"><\/span>\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230REDIST\u91cd\u5206\u5e03\u65f6\uff0c\u7528ID\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; explain select id,name,count(*) from t1 group by id,name;\n+----+--------------+-----------+---------+-------------------+\n| ID | MOTION       | OPERATION | TABLE   | CONDITION         |\n+----+--------------+-----------+---------+-------------------+\n| 01 | &#91;RESULT]     |  Step     | &lt;00&gt;    |                   |\n|    |              |  GROUP    |         | GROUP BY id, name |\n| 00 | &#91;REDIST(id)] |  Table    | t1&#91;DIS] |                   |\n|    |              |  GROUP    |         | GROUP BY id, name |\n+----+--------------+-----------+---------+-------------------+\n4 rows in set (Elapsed: 00:00:00.01)\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-2\"><\/span>\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u4fee\u6539\u53c2\u6570\u7b49\u4e8e1\u540e\uff0c\u91cd\u5206\u5e03REDIST\u91c7\u7528\u4e86id,name\u4e24\u4e2a\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase&gt; set _t_gcluster_hash_redistribute_groupby_on_multiple_expression=1;\nQuery OK, 0 rows affected (Elapsed: 00:00:00.00)\n\ngbase&gt; explain select id,name,count(*) from t1 group by id,name;\n+----+-------------------+-----------+---------+-------------------+\n| ID | MOTION            | OPERATION | TABLE   | CONDITION         |\n+----+-------------------+-----------+---------+-------------------+\n| 01 | &#91;RESULT]          |  Step     | &lt;00&gt;    |                   |\n|    |                   |  GROUP    |         | GROUP BY id, name |\n| 00 | &#91;REDIST(id,name)] |  Table    | t1&#91;DIS] |                   |\n|    |                   |  GROUP    |         | GROUP BY id, name |\n+----+-------------------+-----------+---------+-------------------+\n4 rows in set (Elapsed: 00:00:00.00)\n<\/code><\/pre>\n\n\n\n<p><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"join_%E6%93%8D%E4%BD%9C\"><\/span>join \u64cd\u4f5c<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0-3\"><\/span>\u53c2\u6570<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u9ed8\u8ba4\u503c\u4e3a1\uff0c\u53ef\u9009\u503c\u4e3a1\u548c2\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>_t_gcluster_join_multi_hash_optimize_level=<\/code><\/pre>\n\n\n\n<p>\u53c2\u6570\u4e3a1\uff0c\u6309\u7167\u5355\u5217\u8ba1\u7b97\u8fdb\u884chash\u91cd\u5206\u5e03<br>\u53c2\u6570\u4e3a2\uff0c\u6309\u7167\u591a\u5217\u8ba1\u7b97\u8fdb\u884c\u91cd\u5206\u5e03<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%AF%B4%E6%98%8E-3\"><\/span>\u8bf4\u660e<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u5e38\u91cf\u3001\u6807\u91cf\u5b50\u67e5\u8be2\u4e0d\u4f1a\u4f5c\u4e3a\u91cd\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<p>\u8bbe\u7f6e\u8be5\u53c2\u6570\u4e3a2\uff0c\u7531\u4e8e\u5728hash\u9636\u6bb5\u8ba1\u7b97\u4e86\u591a\u4e2a\u5217\uff0c\u968f\u7740hash\u6761\u4ef6\u5217\u7684\u589e\u591a\uff0c\u8ba1\u7b97\u6210\u672c\u589e\u52a0\uff0c\u65f6\u95f4\u589e\u957f\uff0c\u6240\u4ee5\u8981\u4ee5\u6d4b\u8bd5\u7ed3\u679c\u4e3a\u51c6\uff0c\u5728\u6570\u636e\u503e\u659c\u548c\u6027\u80fd\u4e4b\u95f4\u5e73\u8861\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%A0%B7%E4%BE%8B-3\"><\/span>\u6837\u4f8b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A1%A8%E7%BB%93%E6%9E%84-3\"><\/span>\u8868\u7ed3\u6784<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u5982\u4e0b\u662f2\u4e2a\u968f\u673a\u5206\u5e03\u8868\uff0c\u6ca1\u6709hash\u5206\u5e03\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase> desc t1;\n+-------+--------------+------+-----+---------+-------+\n| Field | Type         | Null | Key | Default | Extra |\n+-------+--------------+------+-----+---------+-------+\n| id    | int(11)      | YES  |     | NULL    |       |\n| name  | varchar(100) | YES  |     | NULL    |       |\n+-------+--------------+------+-----+---------+-------+\n2 rows in set (Elapsed: 00:00:00.00)\n\ngbase> show create table t1;\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| Table | Create Table                                                                                                                                          |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n| t1    | CREATE TABLE \"t1\" (\n  \"id\" int(11) DEFAULT NULL,\n  \"name\" varchar(100) DEFAULT NULL\n) ENGINE=EXPRESS DEFAULT CHARSET=utf8 TABLESPACE='sys_tablespace' |\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\n1 row in set (Elapsed: 00:00:00.00)\n\ngbase> show create table t3;\r\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\r\n| Table | Create Table                                                                                                                                          |\r\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\r\n| t3    | CREATE TABLE \"t3\" (\r\n  \"id\" int(11) DEFAULT NULL,\r\n  \"name\" varchar(100) DEFAULT NULL\r\n) ENGINE=EXPRESS DEFAULT CHARSET=utf8 TABLESPACE='sys_tablespace' |\r\n+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------+\r\n1 row in set (Elapsed: 00:00:00.00)\r\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%BB%98%E8%AE%A4%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-3\"><\/span>\u9ed8\u8ba4\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u53ef\u4ee5\u770b\u5230REDIST\u91cd\u5206\u5e03\u65f6\uff0c\u7528\u4e86name\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase> explain select t1.id,t1.name from t1 left join t3 on t1.id=t3.id and t1.name=t3.name;\r\n+----+----------------+------------+---------+-----------------------------+\r\n| ID | MOTION         | OPERATION  | TABLE   | CONDITION                   |\r\n+----+----------------+------------+---------+-----------------------------+\r\n| 02 | &#91;RESULT]       |  LEFT JOIN |         | (id = id) AND (name = name) |\r\n|    |                |   Step     | &lt;00>    |                             |\r\n|    |                |   Step     | &lt;01>    |                             |\r\n| 01 | &#91;REDIST(name)] |  Table     | t3&#91;DIS] |                             |\r\n| 00 | &#91;REDIST(name)] |  Table     | t1&#91;DIS] |                             |\r\n+----+----------------+------------+---------+-----------------------------+\r\n5 rows in set (Elapsed: 00:00:00.00)\r\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E6%95%B0%E5%90%8E%E7%9A%84%E6%89%A7%E8%A1%8C%E8%AE%A1%E5%88%92-3\"><\/span>\u53c2\u6570\u540e\u7684\u6267\u884c\u8ba1\u5212<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u4fee\u6539\u53c2\u6570\u7b49\u4e8e2\u540e\uff0c\u91cd\u5206\u5e03REDIST\u91c7\u7528\u4e86id,name\u4e24\u4e2a\u5217\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase> set _t_gcluster_join_multi_hash_optimize_level=2;\r\nQuery OK, 0 rows affected (Elapsed: 00:00:00.00)\n\ngbase> explain select t1.id,t1.name from t1 left join t3 on t1.id=t3.id and t1.name=t3.name;\r\n+----+-------------------+------------+---------+-----------------------------+\r\n| ID | MOTION            | OPERATION  | TABLE   | CONDITION                   |\r\n+----+-------------------+------------+---------+-----------------------------+\r\n| 02 | &#91;RESULT]          |  LEFT JOIN |         | (id = id) AND (name = name) |\r\n|    |                   |   Step     | &lt;00>    |                             |\r\n|    |                   |   Step     | &lt;01>    |                             |\r\n| 01 | &#91;REDIST(id,name)] |  Table     | t3&#91;DIS] |                             |\r\n| 00 | &#91;REDIST(id,name)] |  Table     | t1&#91;DIS] |                             |\r\n+----+-------------------+------------+---------+-----------------------------+\r\n5 rows in set (Elapsed: 00:00:00.01)\r\n<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%B3%A8%E6%84%8F\"><\/span>\u6ce8\u610f<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>\u6709\u65f6\u4e00\u4e2a\u8868\u4f1a\u62c9\u6210\u590d\u5236\u8868\uff0c\u4e0d\u4f1a\u53c2\u4e0e\u91cd\u5206\u5e03\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gbase> explain select t1.id,t1.name from t1 left join t3 on t1.id=t3.id and t1.name=t3.name;\r\n+----+-------------+------------+---------+-----------------------------+\r\n| ID | MOTION      | OPERATION  | TABLE   | CONDITION                   |\r\n+----+-------------+------------+---------+-----------------------------+\r\n| 01 | &#91;RESULT]    |  LEFT JOIN |         | (id = id) AND (name = name) |\r\n|    |             |   Table    | t1&#91;DIS] |                             |\r\n|    |             |   Step     | &lt;00>    |                             |\r\n| 00 | &#91;BROADCAST] |  Table     | t3&#91;DIS] |                             |\r\n+----+-------------+------------+---------+-----------------------------+\r\n4 rows in set (Elapsed: 00:00:00.00)\r\n<\/code><\/pre>\n\n\n\n<p>\u9700\u8981\u901a\u8fc7\u5982\u4e0b\u53c2\u6570\u8fdb\u884c\u8c03\u4f18\uff0c\u4f46\u4e5f\u8bb8\u62c9\u590d\u5236\u8868\u6027\u80fd\u66f4\u597d\u5462\uff1f\u8fd8\u662f\u4ee5\u6d4b\u8bd5\u7ed3\u679c\u4e3a\u51c6\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>gcluster_hash_redistribute_join_optimize=1<\/code><\/pre>\n\n\n\n<p>\u8be5\u53c2\u6570\u8be6\u60c5\u53c2\u8003 <a href=\"https:\/\/www.gbase8.cn\/en\/3560\/\">GBase 8a\u6027\u80fd\u4f18\u5316\u6848\u4f8b\uff0c\u5927\u91cf\u5c0f\u8868join\u65f6\u62c9\u4e86\u590d\u5236\u8868\u5bfc\u81f4\u53ea\u67091\u4e2a\u8282\u70b9\u8fd0\u884c\uff0cgcluster_hash_redistribute_join_optimize \u53c2\u6570\u8c03\u6574<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%8F%82%E8%80%83\"><\/span><br>\u53c2\u8003<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><a href=\"https:\/\/www.gbase8.cn\/en\/3600\/\">GBase 8a \u6267\u884c\u8ba1\u5212Explain\u4ecb\u7ecd<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>\u5728\u6267\u884cdistinct\u3001group\u3001join\u662f\u7531\u591a\u4e2a\u5217\u53c2\u6570\u65f6\uff0c\u5982\u679c\u6295\u5f71\u5217\u91cc\u6ca1\u6709Hash\u5206\u5e03\u5217\uff0c\u5219\u4f1a\u9009\u62e9\u4e00\u4e2a\u5217\u505ahash\u52a8\u6001\u91cd\u5206\u5e03\u3002GBase 8a\u6570\u636e\u5e93\u96c6\u7fa4\u901a\u8fc7_t_gcluster_distinct_multi_redist\u548c_t_gcluster_hash_redistribute_groupby_on_multiple_expression\u53c2\u6570\uff0c\u53ef\u4ee5\u6307\u5b9a\u591a\u4e2a\u5217\u53c2\u4e0ehash\u8ba1\u7b97\uff0c\u907f\u514dGBase 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