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Posted to commits@doris.apache.org by GitBox <gi...@apache.org> on 2019/11/29 08:06:37 UTC
[GitHub] [incubator-doris] EmmyMiao87 commented on issue #2270: Where stmt中支持结果为非 Scalar 类型的子查询
EmmyMiao87 commented on issue #2270: Where stmt中支持结果为非 Scalar 类型的子查询
URL: https://github.com/apache/incubator-doris/issues/2270#issuecomment-559698155
# 改进设计
经讨论，由于之后查询层会重构，所以本次支持 TPC-DS 的语句原则为简单快速，而非通用。
所以将 assert node 功能改为 assert row count node。此节点仅支持判断下层节点返回行数是否为指定行数。如果超过指定函数，则查询失败
比如对于查询：
```
select k2 from nullable_table where k1=(select k2 from nullable_table);
```
查询规划：assert row count node 是 1，也就是下层最多有一行结果，否则查询失败。
```
+---------------------------------------------------+
| Explain String |
+---------------------------------------------------+
| PLAN FRAGMENT 0 |
| OUTPUT EXPRS:`k2` | |
| PARTITION: UNPARTITIONED |
| |
| RESULT SINK |
| |
| 6:EXCHANGE |
| tuple ids: 0 1 |
| |
| PLAN FRAGMENT 1 |
| OUTPUT EXPRS: |
| PARTITION: RANDOM |
| |
| STREAM DATA SINK |
| EXCHANGE ID: 06 |
| UNPARTITIONED |
| |
| 3:HASH JOIN |
| | join op: LEFT SEMI JOIN (BROADCAST) |
| | hash predicates: |
| | colocate: false, reason: Node type not match |
| `k1` = `k2` |
| | tuple ids: 0 1 |
| | |
| |----5:EXCHANGE |
| | tuple ids: 1 |
| | |
| 0:OlapScanNode |
| TABLE: nullable_table |
| PREAGGREGATION: ON |
| partitions=1/1 |
| rollup: nullable_table |
| buckets=10/10 |
| cardinality=3 |
| avgRowSize=1977.6666 |
| numNodes=1 |
| tuple ids: 0 |
| |
| PLAN FRAGMENT 2 |
| OUTPUT EXPRS: |
| PARTITION: UNPARTITIONED |
| |
| STREAM DATA SINK |
| EXCHANGE ID: 05 |
| UNPARTITIONED |
| |
| 2:ASSERT ROW COUNT |
| | assert row count: 1 |
| | tuple ids: 1 |
| | |
| 4:EXCHANGE |
| tuple ids: 1 |
| |
| PLAN FRAGMENT 3 |
| OUTPUT EXPRS: |
| PARTITION: RANDOM |
| |
| STREAM DATA SINK |
| EXCHANGE ID: 04 |
| UNPARTITIONED |
| |
| 1:OlapScanNode |
| TABLE: nullable_table |
| PREAGGREGATION: ON |
| partitions=1/1 |
| rollup: nullable_table |
| buckets=10/10 |
| cardinality=3 |
| avgRowSize=1977.6666 |
| numNodes=1 |
| tuple ids: 1 |
+---------------------------------------------------+
```
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