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*: update the row count display of probe side of IndexJoin and Apply (pingcap#10864)
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‎correlated-subquery-optimization.md‎

Lines changed: 28 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -57,20 +57,20 @@ explain select * from t1 where t1.a < (select /*+ NO_DECORRELATE() */ sum(t2.a)
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```
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```sql
60-
+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| id | estRows | task | access object | operator info |
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+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| Projection_10 | 10000.00 | root | | test.t1.a, test.t1.b |
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| └─Apply_12 | 10000.00 | root | | CARTESIAN inner join, other cond:lt(cast(test.t1.a, decimal(10,0) BINARY), Column#7) |
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| ├─TableReader_14(Build) | 10000.00 | root | | data:TableFullScan_13 |
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| │ └─TableFullScan_13 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo |
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| └─MaxOneRow_15(Probe) | 1.00 | root | | |
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| └─HashAgg_27 | 1.00 | root | | funcs:sum(Column#10)->Column#7 |
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| └─IndexLookUp_28 | 1.00 | root | | |
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| ├─IndexRangeScan_25(Build) | 10.00 | cop[tikv] | table:t2, index:idx(b) | range: decided by [eq(test.t2.b, test.t1.b)], keep order:false, stats:pseudo |
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| └─HashAgg_17(Probe) | 1.00 | cop[tikv] | | funcs:sum(test.t2.a)->Column#10 |
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| └─TableRowIDScan_26 | 10.00 | cop[tikv] | table:t2 | keep order:false, stats:pseudo |
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+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| id | estRows | task | access object | operator info |
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| Projection_10 | 10000.00 | root | | test.t1.a, test.t1.b |
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| └─Apply_12 | 10000.00 | root | | CARTESIAN inner join, other cond:lt(cast(test.t1.a, decimal(10,0) BINARY), Column#7) |
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| ├─TableReader_14(Build) | 10000.00 | root | | data:TableFullScan_13 |
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| │ └─TableFullScan_13 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo |
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| └─MaxOneRow_15(Probe) | 10000.00 | root | | |
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| └─StreamAgg_20 | 10000.00 | root | | funcs:sum(Column#14)->Column#7 |
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| └─Projection_45 | 100000.00 | root | | cast(test.t2.a, decimal(10,0) BINARY)->Column#14 |
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| └─IndexLookUp_44 | 100000.00 | root | | |
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| ├─IndexRangeScan_42(Build) | 100000.00 | cop[tikv] | table:t2, index:idx(b) | range: decided by [eq(test.t2.b, test.t1.b)], keep order:false, stats:pseudo |
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| └─TableRowIDScan_43(Probe) | 100000.00 | cop[tikv] | table:t2 | keep order:false, stats:pseudo |
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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```
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Disabling the decorrelation rule can also achieve the same effect:
@@ -84,20 +84,20 @@ explain select * from t1 where t1.a < (select sum(t2.a) from t2 where t2.b = t1.
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```
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```sql
87-
+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| id | estRows | task | access object | operator info |
89-
+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| Projection_10 | 10000.00 | root | | test.t1.a, test.t1.b |
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| └─Apply_12 | 10000.00 | root | | CARTESIAN inner join, other cond:lt(cast(test.t1.a, decimal(10,0) BINARY), Column#7) |
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| ├─TableReader_14(Build) | 10000.00 | root | | data:TableFullScan_13 |
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| │ └─TableFullScan_13 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo |
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| └─MaxOneRow_15(Probe) | 1.00 | root | | |
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| └─HashAgg_27 | 1.00 | root | | funcs:sum(Column#10)->Column#7 |
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| └─IndexLookUp_28 | 1.00 | root | | |
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| ├─IndexRangeScan_25(Build) | 10.00 | cop[tikv] | table:t2, index:idx(b) | range: decided by [eq(test.t2.b, test.t1.b)], keep order:false, stats:pseudo |
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| └─HashAgg_17(Probe) | 1.00 | cop[tikv] | | funcs:sum(test.t2.a)->Column#10 |
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| └─TableRowIDScan_26 | 10.00 | cop[tikv] | table:t2 | keep order:false, stats:pseudo |
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+----------------------------------------+----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| id | estRows | task | access object | operator info |
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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| Projection_10 | 10000.00 | root | | test.t1.a, test.t1.b |
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| └─Apply_12 | 10000.00 | root | | CARTESIAN inner join, other cond:lt(cast(test.t1.a, decimal(10,0) BINARY), Column#7) |
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| ├─TableReader_14(Build) | 10000.00 | root | | data:TableFullScan_13 |
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| │ └─TableFullScan_13 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo |
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| └─MaxOneRow_15(Probe) | 10000.00 | root | | |
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| └─StreamAgg_20 | 10000.00 | root | | funcs:sum(Column#14)->Column#7 |
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| └─Projection_45 | 100000.00 | root | | cast(test.t2.a, decimal(10,0) BINARY)->Column#14 |
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| └─IndexLookUp_44 | 100000.00 | root | | |
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| ├─IndexRangeScan_42(Build) | 100000.00 | cop[tikv] | table:t2, index:idx(b) | range: decided by [eq(test.t2.b, test.t1.b)], keep order:false, stats:pseudo |
99+
| └─TableRowIDScan_43(Probe) | 100000.00 | cop[tikv] | table:t2 | keep order:false, stats:pseudo |
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+------------------------------------------+-----------+-----------+------------------------+--------------------------------------------------------------------------------------+
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```
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After disabling the subquery decorrelation rule, you can see `range: decided by [eq(test.t2.b, test.t1.b)]` in `operator info` of `IndexRangeScan_25(Build)`. It means that the decorrelation of correlated subquery is not performed and TiDB uses the index range query.

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