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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2020/04/27 03:10:37 UTC
[GitHub] [flink] godfreyhe commented on a change in pull request #11892: [FLINK-17112][table] Support DESCRIBE statement in Flink SQL
godfreyhe commented on a change in pull request #11892:
URL: https://github.com/apache/flink/pull/11892#discussion_r415473253
##########
File path: flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/api/internal/TableEnvImpl.scala
##########
@@ -721,6 +721,15 @@ abstract class TableEnvImpl(
dropViewOperation.isIfExists)
}
TableResultImpl.TABLE_RESULT_OK
+ case descOperation: DescribeTableOperation =>
+ val result = catalogManager.getTable(descOperation.getSqlIdentifier)
+ if (result.isPresent) {
+ buildShowResult(Array(result.get().getTable.getSchema.toString))
Review comment:
I find the print (through `TableResult#print`) result of `describe xx` looks a little strange:
```
+--------------------------------+
| result |
+--------------------------------+
| root
|-- a: INT
|-- b: S... |
+--------------------------------+
1 row in set
```
Users have to parse the unstructured result if he/she want to use the result to do sth through TableResult#collect method.
How about we return a structured tableau result, e.g.
```
+-------------+---------+-------------+
| name | type | comment |
+-------------+---------+-------------+
| a | INT | |
| b | STRING | |
+-------------+---------+-------------+
2 rows in set
```
This is different from the describe result in SQL client.
Anther thing we should consider is how to print `watermarkSpecs` and compute column.
How about we add a column named `expr` to represent `watermarkSpecs` and compute column.
```
+-------------+-------------+-------------+-------------+
| name | type | comment | expr |
+-------------+-------------+-------------+-------------+
| a | INT | | (NULL) |
| b | INT | | a + 1 |
| c |TIMESTAMP(3) | | (NULL) |
| WATERMARK | (NULL) | | c AS now() |
+-------------+-------------+-------------+-------------+
```
##########
File path: flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/api/internal/TableEnvImpl.scala
##########
@@ -721,6 +721,15 @@ abstract class TableEnvImpl(
dropViewOperation.isIfExists)
}
TableResultImpl.TABLE_RESULT_OK
+ case descOperation: DescribeTableOperation =>
+ val result = catalogManager.getTable(descOperation.getSqlIdentifier)
+ if (result.isPresent) {
+ buildShowResult(Array(result.get().getTable.getSchema.toString))
Review comment:
cc @twalthr
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