Commits
alamb authored and Andy Grove committed 2dcc9a1031a
ARROW-9654: [Rust][DataFusion] Add `EXPLAIN <SQL>` statement
In order to help users and developers understand what DataFusion's planner is doing, this PR adds an `"EXPLAIN PLAN"` feature. All other database systems I have worked with have such a feature (e.g. see [MySql](https://dev.mysql.com/doc/refman/8.0/en/explain-output.html)).
Example printout (the plans printed are simply the `std::fmt::Debug` representation of the plan structures:)
```
> explain SELECT status, COUNT(1) FROM http_api_requests_total WHERE path = '/api/v2/write' GROUP BY status;
+--------------+----------------------------------------------------------------------+
| plan_type | plan |
+--------------+----------------------------------------------------------------------+
| logical_plan | Aggregate: groupBy=[[#status]], aggr=[[COUNT(UInt8(1))]] |
| | Selection: #path Eq Utf8("/api/v2/write") And #path Eq Utf8("foo") |
| | TableScan: http_api_requests_total projection=None |
+--------------+----------------------------------------------------------------------+
1 rows in set. Query took 0 seconds.
```
and
```
> explain VERBOSE SELECT status, COUNT(1) FROM http_api_requests_total WHERE path = '/api/v2/write' GROUP BY status;
+-----------------------------------------+----------------------------------------------------------------------+
| plan_type | plan |
+-----------------------------------------+----------------------------------------------------------------------+
| logical_plan | Aggregate: groupBy=[[#status]], aggr=[[COUNT(UInt8(1))]] |
| | Selection: #path Eq Utf8("/api/v2/write") And #path Eq Utf8("foo") |
| | TableScan: http_api_requests_total projection=None |
| logical_plan after projection_push_down | Aggregate: groupBy=[[#status]], aggr=[[COUNT(UInt8(1))]] |
| | Selection: #path Eq Utf8("/api/v2/write") And #path Eq Utf8("foo") |
| | TableScan: http_api_requests_total projection=Some([6, 8]) |
| logical_plan after type_coercion | Aggregate: groupBy=[[#status]], aggr=[[COUNT(UInt8(1))]] |
| | Selection: #path Eq Utf8("/api/v2/write") And #path Eq Utf8("foo") |
| | TableScan: http_api_requests_total projection=Some([6, 8]) |
| physical_plan | HashAggregateExec { |
| | group_expr: [ |
| | Column { |
| | name: "status", |
| | }, |
| | ], |
| | aggr_expr: [ |
| | Count { |
| | expr: Literal { |
| | value: UInt8( |
| | 1, |
| | ), |
| | }, |
| | }, |
| | ], |
| | input: SelectionExec { |
| | expr: BinaryExpr { |
| | left: BinaryExpr { |
| | left: Column { |
| | name: "path", |
| | }, |
| | op: Eq, |
| | right: Literal { |
| | value: Utf8( |
| | "/api/v2/write", |
| | ), |
| | }, |
| | }, |
| | op: And, |
| | right: BinaryExpr { |
| | left: Column { |
| | name: "path", |
| | }, |
| | op: Eq, |
| | right: Literal { |
| | value: Utf8( |
| | "foo", |
| | ), |
| | }, |
| | }, |
| | }, |
| | input: DataSourceExec { |
| | schema: Schema { |
| | fields: [ |
| | Field { |
| | name: "path", |
| | data_type: Utf8, |
| | nullable: true, |
| | dict_id: 0, |
| | dict_is_ordered: false, |
| | }, |
| | Field { |
| | name: "status", |
| | data_type: Utf8, |
| | nullable: true, |
| | dict_id: 0, |
| | dict_is_ordered: false, |
| | }, |
| | ], |
| | metadata: {}, |
| | }, |
| | partitions.len: 1, |
| | }, |
| | }, |
| | schema: Schema { |
| | fields: [ |
| | Field { |
| | name: "status", |
| | data_type: Utf8, |
| | nullable: true, |
| | dict_id: 0, |
| | dict_is_ordered: false, |
| | }, |
| | Field { |
| | name: "COUNT(UInt8(1))", |
| | data_type: UInt64, |
| | nullable: true, |
| | dict_id: 0, |
| | dict_is_ordered: false, |
| | }, |
| | ], |
| | metadata: {}, |
| | }, |
| | } |
+-----------------------------------------+----------------------------------------------------------------------+
4 row in set. Query took 0 seconds.
```
Closes #7959 from alamb/alamb/ARROW-9654-explain
Authored-by: alamb <andrew@nerdnetworks.org>
Signed-off-by: Andy Grove <andygrove73@gmail.com>