This patch uses the "external data source" mechanism in Impala to
implement data source for querying JDBC.
It has some limitations due to the restrictions of "external data
source":
- It is not distributed, e.g, fragment is unpartitioned. The queries
are executed on coordinator.
- Queries which read following data types from external JDBC tables
are not supported:
BINARY, CHAR, DATETIME, and COMPLEX.
- Only support binary predicates with operators =, !=, <=, >=,
<, > to be pushed to RDBMS.
- Following data types are not supported for predicates:
DECIMAL, TIMESTAMP, DATE, and BINARY.
- External tables with complex types of columns are not supported.
- Support is limited to the following databases:
MySQL, Postgres, Oracle, MSSQL, H2, DB2, and JETHRO_DATA.
- Catalog V2 is not supported (IMPALA-7131).
- DataSource objects are not persistent (IMPALA-12375).
Additional fixes are planned on top of this patch.
Source files under jdbc/conf, jdbc/dao and jdbc/exception are
replicated from Hive JDBC Storage Handler.
In order to query the RDBMS tables, the following steps should be
followed (note that existing data source table will be rebuilt):
1. Make sure the Impala cluster has been started.
2. Copy the jar files of JDBC drivers and the data source library into
HDFS.
${IMPALA_HOME}/testdata/bin/copy-ext-data-sources.sh
3. Create an `alltypes` table in the Postgres database.
${IMPALA_HOME}/testdata/bin/load-ext-data-sources.sh
4. Create data source tables (alltypes_jdbc_datasource and
alltypes_jdbc_datasource_2).
${IMPALA_HOME}/bin/impala-shell.sh -f\
${IMPALA_HOME}/testdata/bin/create-ext-data-source-table.sql
5. It's ready to run query to access data source tables created
in last step. Don't need to restart Impala cluster.
Testing:
- Added unit-test for Postgres and ran unit-test with JDBC driver
postgresql-42.5.1.jar.
- Ran manual unit-test for MySql with JDBC driver
mysql-connector-j-8.1.0.jar.
- Ran core tests successfully.
Change-Id: I8244e978c7717c6f1452f66f1630b6441392e7d2
Reviewed-on: http://gerrit.cloudera.org:8080/17842
Reviewed-by: Wenzhe Zhou <wzhou@cloudera.com>
Reviewed-by: Kurt Deschler <kdeschle@cloudera.com>
Reviewed-by: Riza Suminto <riza.suminto@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
