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reference/performance: specify index name of primary key for USE_INDEX_MERGE (#2350) #2640

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sre-bot merged 1 commit into from
Apr 7, 2020
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reference/performance: specify index name of primary key for USE_INDEX_MERGE (#2350) #2640

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4 changes: 4 additions & 0 deletions reference/performance/optimizer-hints.md
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,10 @@ select /*+ READ_FROM_STORAGE(TIFLASH[t1], TIKV[t2]) */ t1.a from t t1, t t2 wher
select /*+ USE_INDEX_MERGE(t1, idx_a, idx_b, idx_c) */ * from t t1 where t1.a > 10 or t1.b > 10;
```

> **注意：**
>
> `USE_INDEX_MERGE` 的参数是索引名，而不是列名。对于主键索引，索引名为 `primary`。

### NO_INDEX_MERGE()

`NO_INDEX_MERGE()` 会关闭优化器的 index merge 功能。
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