SELECT INTO · k8s原理与实践

# SELECT INTO SELECT INTO 算子用于将查询结果赋值给变量列表，查询仅返回一行数据。如下示例查询中，`SELECT`输出列为`COUNT(*)`和`MAX(c1)`，其查询结果分别赋值给变量 @a 和 @b。 ~~~ obclient>CREATE TABLE t1(c1 INT, c2 INT); Query OK, 0 rows affected (0.12 sec) obclient>INSERT INTO t1 VALUES(1,1); Query OK, 1 rows affected (0.12 sec) obclient>INSERT INTO t1 VALUES(2,2); Query OK, 1 rows affected (0.12 sec) obclient>EXPLAIN SELECT COUNT(*), MAX(c1) INTO @a, @b FROM t1\G; *************************** 1. row *************************** Query Plan: ========================================= |ID|OPERATOR |NAME|EST. ROWS|COST| ----------------------------------------- |0 |SELECT INTO | |0 |37 | |1 | SCALAR GROUP BY| |1 |37 | |2 | TABLE SCAN |t1 |2 |37 | ========================================= Outputs & filters: ------------------------------------- 0 - output([T_FUN_COUNT(*)], [T_FUN_MAX(t1.c1)]), filter(nil) 1 - output([T_FUN_COUNT(*)], [T_FUN_MAX(t1.c1)]), filter(nil), group(nil), agg_func([T_FUN_COUNT(*)], [T_FUN_MAX(t1.c1)]) 2 - output([t1.c1]), filter(nil), access([t1.c1]), partitions(p0) ~~~ 上述示例中，执行计划展示中的 outputs & filters 详细列出了 SELECT INTO 算子的输出信息如下： <div data-card-value="data:%7B%22rows%22%3A3%2C%22cols%22%3A2%2C%22html%22%3A%22%3Ctable%20class%3D%5C%22lake-table%5C%22%20style%3D%5C%22width%3A%20748px%3B%5C%22%3E%3Ccolgroup%3E%3Ccol%20span%3D%5C%221%5C%22%20width%3D%5C%22139%5C%22%20%2F%3E%3Ccol%20span%3D%5C%221%5C%22%20width%3D%5C%22609%5C%22%20%2F%3E%3C%2Fcolgroup%3E%3Ctbody%3E%3Ctr%20style%3D%5C%22height%3A%2033px%3B%5C%22%3E%3Ctd%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cp%20data-lake-id%3D%5C%22b92b778e0b6d42b6559f0dbdfd18725c%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%20style%3D%5C%22color%3A%20%23262626%3B%5C%22%3E%3Cstrong%3E%E4%BF%A1%E6%81%AF%E5%90%8D%E7%A7%B0%3C%2Fstrong%3E%3C%2Fspan%3E%3C%2Fp%3E%3C%2Ftd%3E%3Ctd%20rowspan%3D%5C%221%5C%22%20colspan%3D%5C%221%5C%22%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%20style%3D%5C%22color%3A%20%23262626%3B%5C%22%3E%3Cstrong%3E%3Cspan%3E%E5%90%AB%E4%B9%89%3C%2Fspan%3E%3C%2Fstrong%3E%3C%2Fspan%3E%3C%2Ftd%3E%3C%2Ftr%3E%3Ctr%20style%3D%5C%22height%3A%2033px%3B%5C%22%3E%3Ctd%20rowspan%3D%5C%221%5C%22%20colspan%3D%5C%221%5C%22%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%3Eoutput%3C%2Fspan%3E%3C%2Ftd%3E%3Ctd%20rowspan%3D%5C%221%5C%22%20colspan%3D%5C%221%5C%22%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%3E%E8%AF%A5%E7%AE%97%3Cspan%3E%E5%AD%90%E8%B5%8B%E5%80%BC%E7%BB%99%E5%8F%98%E9%87%8F%E5%88%97%E8%A1%A8%E7%9A%84%E8%A1%A8%E8%BE%BE%E5%BC%8F%3C%2Fspan%3E%E3%80%82%3C%2Fspan%3E%3C%2Ftd%3E%3C%2Ftr%3E%3Ctr%20style%3D%5C%22height%3A%2033px%3B%5C%22%3E%3Ctd%20rowspan%3D%5C%221%5C%22%20colspan%3D%5C%221%5C%22%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%3Efilter%3C%2Fspan%3E%3C%2Ftd%3E%3Ctd%20rowspan%3D%5C%221%5C%22%20colspan%3D%5C%221%5C%22%20style%3D%5C%22vertical-align%3A%20top%3B%5C%22%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%3E%3Cspan%3E%3Cspan%3E%E8%AF%A5%E7%AE%97%E5%AD%90%E4%B8%8A%E7%9A%84%E8%BF%87%E6%BB%A4%E6%9D%A1%E4%BB%B6%E3%80%82%3C%2Fspan%3E%3C%2Fspan%3E%3Cspan%3E%E7%94%B1%E4%BA%8E%C2%A0%3C%2Fspan%3E%3Cspan%20class%3D%5C%22lake-fontsize-11%5C%22%3E%3Cspan%3Eselect%20into%3C%2Fspan%3E%3C%2Fspan%3E%3Cspan%3E%3Cspan%3E%C2%A0%E7%AE%97%E5%AD%90%E6%B2%A1%E6%9C%89%20filter%3C%2Fspan%3E%3C%2Fspan%3E%3Cspan%3E%EF%BC%8C%E6%89%80%E4%BB%A5%E4%B8%BA%20nil%3C%2Fspan%3E%E3%80%82%3C%2Fspan%3E%3C%2Ftd%3E%3C%2Ftr%3E%3C%2Ftbody%3E%3C%2Ftable%3E%22%2C%22margin%22%3Afalse%2C%22hideBorder%22%3Afalse%2C%22id%22%3A%22lMx1D%22%7D" id="lMx1D" data-tag="div" class="div"><table data-tag="table" id="table-tv5-ot1-6ce" class="table"><colgroup span="1" width="139" data-tag="col" id="col-ij8-d3m-rjw" colwidth="1*" colnum="1" colname="col1" style="width:50%" class="col"></colgroup><colgroup span="1" width="609" data-tag="col" id="col-c3k-ijk-6jx" colwidth="1*" colnum="2" colname="col2" style="width:50%" class="col"></colgroup><thead id="thead-sw2-y9p-7qr" class="thead"><tr id="tr-obu-hf0-69k"><th id="td-est-jht-40j"><p id="p-6zk-wzn-wg8"><b>信息名称</b></p></th><th id="td-xlq-cwo-3eo"><p id="p-2q6-k8a-ity"><b>含义</b></p></th></tr></thead><tbody data-tag="tbody" id="tbody-22j-6nf-6mr" class="tbody"><tr data-tag="tr" id="tr-2f1-6wb-xbt" class="tr"><td data-tag="td" id="td-twb-05y-j5s" class="td"><p id="p-dqv-arz-q8w">output</p></td><td data-tag="td" id="td-oig-5ts-9zp" class="td"><p id="p-u42-fqd-yip">该算子赋值给变量列表的表达式。</p></td></tr><tr data-tag="tr" id="tr-o7q-v9u-rub" class="tr"><td data-tag="td" id="td-j84-b5i-lti" class="td"><p id="p-04a-fgo-6k0">filter</p></td><td data-tag="td" id="td-ei6-b7z-mkx" class="td"><p id="p-71n-19j-6be">该算子上的过滤条件。</p><p id="p-kv3-i48-90r">由于示例中 SELECT INTO 算子没有设置 filter，所以为 nil。</p></td></tr></tbody></table></div>