*: update the row count display of probe side of IndexJoin and Apply by time-and-fate · Pull Request #11624 · pingcap/docs-cn

time-and-fate · 2022-10-13T10:54:46Z

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ti-chi-bot · 2022-10-13T10:54:47Z

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TomShawn · 2022-10-17T03:32:09Z

+> **注意：**
+>
+> 在 v6.4.0 之前的版本中，对于 `IndexJoin` 和 `Apply` 算子的 Probe 端所有子节点的 `estRows`，显示的行数的意义与之后的版本有所不同。
+> 在之前的版本中，这些行数代表对于 Build 端子节点的每一行，Probe 端预计会处理的行数，而不是 Probe 端预计会处理的总行数。由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，因此会有含义上的不一致。


在 v6.4 起的版本中，estRows 的数字代表“Probe 端预计会处理的总行数” 吗？

不太理解由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，因此会有含义上的不一致。这一句。

下面示例没有 EXPLAIN ANALYZE 的返回结果，对 actRows 没有解释；

是什么的总行数呢？与什么的含义上有什么不同呢？

Suggested change

> 在之前的版本中，这些行数代表对于 Build 端子节点的每一行，Probe 端预计会处理的行数，而不是 Probe 端预计会处理的总行数。由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，因此会有含义上的不一致。

> 在 v6.4.0 之前，`estRows` 表示对于 Build 端子节点的每一行，Probe 端预计会处理的行数。自 v6.4.0 起，`estRows` 表示 Probe 端预计会处理的**总行数**。由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，v6.4.0 起这些算子 `estRows` 的含义与 `actRows` 列的含义保持一致。

对这两种算子的 probe 子树，行数有两种可能的表达方式，一种是单次 probe 的行数，一种是总行数。
EXPLAIN ANALYZE 在 actRows 列显示的实际行数总是总行数，而所有估算行数总是单次 probe 的行数，因此这次把估算行数也改成总行数，让他们保持一致。

因为其它情况都总是表示的总行数，不太需要额外解释；只有这两个算子的这种情况，在展示估算行数的时候，以前显示的不是总行数，所以额外解释了一下。

这里我稍微改了下，其它地方除了下面加了个空格，都直接 apply suggestion 了。
PTAL~

time-and-fate · 2022-10-26T06:11:16Z

已更新，PTAL~ @TomShawn

TomShawn · 2022-10-31T03:35:23Z

已更新，PTAL~ @TomShawn

comment 都更新了，请再看下吧。

Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

time-and-fate · 2022-11-07T07:23:43Z

已更新，请再看下吧~ @TomShawn

TomShawn · 2022-11-15T07:23:23Z

/remove-status LGT1
/status LGT2

TomShawn · 2022-11-15T07:23:33Z

/merge

ti-chi-bot · 2022-11-15T07:23:36Z

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*: update the row count display of probe side of IndexJoin and Apply pingcap/docs#10864

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time-and-fate mentioned this pull request Jan 31, 2023

correlated-subquery-optimization, explain-subqueries: update operator IDs in examples #12864

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This was referenced Sep 27, 2023

explain joins: fix the TableReader operator #15103

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explain joins: fix the TableReader operator pingcap/docs#14929

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This was referenced Nov 8, 2023

fix the operator info pingcap/docs#15291

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fix the operator info #15393

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	> 在之前的版本中，这些行数代表对于 Build 端子节点的每一行，Probe 端预计会处理的行数，而不是 Probe 端预计会处理的总行数。由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，因此会有含义上的不一致。
	> 在 v6.4.0 之前，`estRows` 表示对于 Build 端子节点的每一行，Probe 端预计会处理的行数。自 v6.4.0 起，`estRows` 表示 Probe 端预计会处理的总行数。由于 `EXPLAIN ANALYZE` 中展示的实际行数（`actRows` 列）表示的是总行数，v6.4.0 起这些算子 `estRows` 的含义与 `actRows` 列的含义保持一致。

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time-and-fate commented Oct 13, 2022

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