add a new blog #50
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add a new blog #50
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zimulala
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May 4, 2018
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| TiDB 一个查询语句的简单流程：一个语句经过 parser 后会得到一个抽象语法树（AST），首先用经过合法性检查后的 AST 生成一个逻辑计划，接着会进行去关联化、谓词下推、聚合下推等规则化优化，然后通过统计数据计算代价选择最优的物理计划，最后执行。流程如下图 1。 | ||
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tidb-source-code-reading-8.md
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| select sum(s.a),count(t.b) from s join t on s.a = t.a and s.c < 100 and t.c > 10 group bys.a | ||
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| （其中 a 是索引，b 也是索引） |
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这句话跟前面的语句有点不好对应？或者居中显示，或者放到 sql 语句下面？
其他带括号的注释也是
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@zimulala @UNHNQ @xuechunL PTAL