RocMarshal commented on a change in pull request #16962:
URL: https://github.com/apache/flink/pull/16962#discussion_r737454112
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File path: docs/content/docs/connectors/table/jdbc.md
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@@ -458,6 +463,38 @@ SELECT * FROM mydb.`custom_schema.test_table2`;
SELECT * FROM `custom_schema.test_table2`;
```
+### JDBC Catalog for MySQL
+
+#### MySQL Metaspace Mapping
+
+The databases in a MySQL instance are at the same mapping level as the
databases under the catalog registered with `MySQLCatalog`. A MySQL instance
can have multiple databases, each database can have multiple tables.
+In Flink, when querying tables registered by MySQL catalog, users can use
either `database.table_name` or just `table_name`. The default value is the
default database specified when `MySQLCatalog` was created.
+
+Therefore, the metaspace mapping between Flink Catalog and MySQLCatalog is as
following:
+
+| Flink Catalog Metaspace Structure | MySQL Metaspace Structure |
+| :------------------------------------| :-----------------------------------|
+| catalog name (defined in Flink only) | N/A |
+| database name | database name |
+| table name | table_name |
+
+The full path of MySQL table in Flink should be
``"`<catalog>`.`<db>`.`<table>`"``.
+
+Here are some examples to access MySQL tables:
+
+```sql
+-- scan table 'test_table', the default database is 'mydb'.
+SELECT * FROM mysql_catalog.mydb.test_table;
+SELECT * FROM mydb.test_table;
+SELECT * FROM test_table;
+
+-- scan table 'test_table' with the given database.
+SELECT * FROM mysql_catalog.given_database.test_table2;
+SELECT * FROM given_database.test_table2;
+```
+
+<span class="label label-danger">Attention</span> At present, when reading
data from a table, the `YEAR` type is read as the `DATE` type by default, but
writing data in `YEAR` type is not supported by `MySQLCatalog` yet. The same
restrictions apply to the reading and writing of the `GEOMETRY` type. The
`GEOMETRY` type fields will be read as the `BYTES` type by default in reading
data from a table, but the writing of the `GEOMETRY` data type is not supported
by `MySQLCatalog` when writing data into a table.
Review comment:
Thanks a lot for the review. @Airblader .
I kept all existing supported type mappings in flink now. Actually, these
types are readed as bytes .
And GEOMETRY type is not supported in Flink build-in types .
What do you think of making it available after completing GEOMETRY type in
Flink ?
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