In the post " Timeout problem of using Connector/J to connect to MySQL in Tomcat ", I want to increase the test/verification of the connection in the connection pool to prevent the database from thinking that the connection is dead and the Web application server thinks that the connection is still valid. The example in the Tomcat documentation uses validationQuery, but there are still many posts on the Internet that write testQuery. Which one should I use?
It turns out that this is related to the implementation of the connection pool: The connection pool implements the function attribute name
| The Tomcat JDBC Connection Pool | validationQuery |
| The Apache Commons DBCP Connection Pool | validationQuery |
| c3p0 - JDBC3 Connection and Statement Pooling | preferredTestQuery |
| Atomikos: Tomcat Spring ActiveMQ MySQL JMX Integration analyzes the source code of Atomikos data connection pool and finds out testQuery |
testQuery |
In addition, the SQL statements for testing/validating connection pool connections also vary by database:
Efficient SQL test query or validation query that will work across all (or most) databases
DBCP - validationQuery for different Databases
Combining the above two posts, the summary results are as follows:
Database test/validation queries
| MySQL | SELECT 1 |
| PostgreSQL | SELECT 1 |
| Microsoft SQL Server | SELECT 1 |
| SQLite | SELECT 1 |
| H2 | SELECT 1 |
| Ingres | SELECT 1 |
| Oracle | select 1 from dual |
| DB2 | select 1 from sysibm.sysdummy1 或 SELECT current date FROM sysibm.sysdummy1 |
| Apache Derby | VALUES 1 FROM SYSIBM.SYSDUMMY1 或 SELECT 1 FROM SYSIBM.SYSDUMMY1 |
| HSQLDB | SELECT 1 FROM any_existing_table WHERE 1=0 或 SELECT 1 FROM INFORMATION_SCHEMA.SYSTEM_USERS |
| Informix | select count(*) from systables |