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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/12/27 14:08:04 UTC
[GitHub] [arrow-datafusion] Dandandan commented on a change in pull request #1492: subquery rfc
Dandandan commented on a change in pull request #1492:
URL: https://github.com/apache/arrow-datafusion/pull/1492#discussion_r775513155
##########
File path: docs/rfcs/subquery_design.md
##########
@@ -0,0 +1,106 @@
+<!---
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+ http://www.apache.org/licenses/LICENSE-2.0
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied. See the License for the
+ specific language governing permissions and limitations
+ under the License.
+-->
+
+Feature Name: subquery
+
+Status: in-progress
+
+Start Date: 2021-12-27
+
+Authors: xudong.w
+
+RFC PR: #1373
+
+Datafusion Issue: #1209
+
+---
+
+### BackGround
+Datafusion currently only supports subquery in `from`.
+Almost all of the tpch queries that datafusion currently fails are due to unsupported subqueries, such as `exist subquery`, `scalar subquery`.
+To improve the integrity of Datafusion SQL support, and through all TPCH cases, more complete subquery support is needed.
+
+---
+
+### Goals
+1. Support the `Scalar subquery`.
+2. Support the `Exist/Not Exist subquery`.
+3. Support the `In/Not In subquery`.
+4. Support the `Any/Some/All subquery`, currently sqlparser doesn't support Any/AllSubquery expr, I opened an issue to trace. [support Any/AllSubquery exprs](https://github.com/sqlparser-rs/sqlparser-rs/issues/394)
+5. Support the non-correlation subquery and correlation subquery
+
+---
+
+### Non-Goals
+1. Correlation subquery doesn't use a more complex solution to do decorrelation, for this design, I'll use nest-loop to do decorrelation.
+I'll provide some materials about more advanced decorrelation, and we can research them and optimize in subsequent iterations.
+2. Some unusual subqueries won't be supported, such as list subqueries.
+---
+
+### Survey
+
+#### postgresql
+In postgresql, subqueries are classified into sublink and subquery based on where they appear. Sublink occurs in constraints such as WHERE/ON.
+Postgres will try to pull up sublink if possible, the relevant code is in `pull_up_sublinks_jointree_recurse` function. If pull up succeeds, sublink will be converted to join.
+- [NOT IN] -> [Anti] Semi Join
+- [ANY/SOME] -> Semi Join
+- [NOT EXISTS] -> [Anti] Semi Join
+
+**Note that not all sublinks can be pulled up**. Only some simple sublink queries can be pulled up. If contains aggregate functions, sublink won't be pulled up, then there will be a `SubPlan` in `Query Plan` and the upper execution plan and the subquery plan do nested loops to get the final result.
+
+Subqueries and sublinks have similar processing logic, except they are in different locations of queries
+
+
+#### cockroach
+The cockroach's subquery design draws on the ideas in this [paper](https://dl.acm.org/doi/10.1145/1247480.1247598), you can see it to learn more details.
+That's the [decorrelation rules](https://github.com/cockroachdb/cockroach/blob/master/pkg/sql/opt/norm/rules/decorrelate.opt) of the cockroach.
+
+#### materialize
Review comment:
```suggestion
#### Materialize
```
##########
File path: docs/rfcs/subquery_design.md
##########
@@ -0,0 +1,106 @@
+<!---
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+ http://www.apache.org/licenses/LICENSE-2.0
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied. See the License for the
+ specific language governing permissions and limitations
+ under the License.
+-->
+
+Feature Name: subquery
+
+Status: in-progress
+
+Start Date: 2021-12-27
+
+Authors: xudong.w
+
+RFC PR: #1373
+
+Datafusion Issue: #1209
+
+---
+
+### BackGround
+Datafusion currently only supports subquery in `from`.
+Almost all of the tpch queries that datafusion currently fails are due to unsupported subqueries, such as `exist subquery`, `scalar subquery`.
+To improve the integrity of Datafusion SQL support, and through all TPCH cases, more complete subquery support is needed.
+
+---
+
+### Goals
+1. Support the `Scalar subquery`.
+2. Support the `Exist/Not Exist subquery`.
+3. Support the `In/Not In subquery`.
+4. Support the `Any/Some/All subquery`, currently sqlparser doesn't support Any/AllSubquery expr, I opened an issue to trace. [support Any/AllSubquery exprs](https://github.com/sqlparser-rs/sqlparser-rs/issues/394)
+5. Support the non-correlation subquery and correlation subquery
+
+---
+
+### Non-Goals
+1. Correlation subquery doesn't use a more complex solution to do decorrelation, for this design, I'll use nest-loop to do decorrelation.
+I'll provide some materials about more advanced decorrelation, and we can research them and optimize in subsequent iterations.
+2. Some unusual subqueries won't be supported, such as list subqueries.
+---
+
+### Survey
+
+#### postgresql
+In postgresql, subqueries are classified into sublink and subquery based on where they appear. Sublink occurs in constraints such as WHERE/ON.
+Postgres will try to pull up sublink if possible, the relevant code is in `pull_up_sublinks_jointree_recurse` function. If pull up succeeds, sublink will be converted to join.
+- [NOT IN] -> [Anti] Semi Join
+- [ANY/SOME] -> Semi Join
+- [NOT EXISTS] -> [Anti] Semi Join
+
+**Note that not all sublinks can be pulled up**. Only some simple sublink queries can be pulled up. If contains aggregate functions, sublink won't be pulled up, then there will be a `SubPlan` in `Query Plan` and the upper execution plan and the subquery plan do nested loops to get the final result.
+
+Subqueries and sublinks have similar processing logic, except they are in different locations of queries
+
+
+#### cockroach
Review comment:
```suggestion
#### CockroachDB
```
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