Query termination

Canceling queries

When a query is canceled, processing will be stopped in the query engine and in all connectors involved in the query. The semantics of what a connector does in response to a cancellation command depends on the connector implementation. For example, JDBC connectors will asynchronously call cancel on the underlying JDBC driver, which might or might not be compatible with this method.

User query timeouts

User query timeouts in Teiid can be managed on the client-side or the server-side. Timeouts are only relevant for the first record returned. If the first record has not been received by the client within the specified timeout period, a cancel command is issued to the server for the request and no results are returned to the client. The cancel command is issued asynchronously without the client’s intervention.

The JDBC API uses the query timeout set by the java.sql.Statement.setQueryTimeout method. You can also set a default statement timeout via the connection property "QUERYTIMEOUT". ODBC clients can also use QUERYTIMEOUT as an execution property via a set statement to control the default timeout setting. See the Client Developer’s Guide for more on connection/execution properties and set statements.

Server-side timeouts start when the query is received by the engine. Network latency or server load can delays the processing of I/O work after a client issues the query. The timeout will be cancelled if the first result is sent back before the timeout has ended. For more information about setting the query-timeout property for a virtual database, see Virtual database properties. For more information about modifying system properties to set a default query timeout for all queries, see System properties in the Administrator’s Guide.

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