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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 is dependent on the connector implementation. For example, JDBC connectors will asynchronously call cancel on the underlying JDBC driver, which may or may not actually support 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 may also set a default statement timeout via the connection property "QUERYTIMEOUT". ODBC clients may also utilize QUERYTIMEOUT as an execution property via a set statement to control the default timeout setting. See the Client Developers Guide for more on connection/execution properties and set statements.

Server-side timeouts start when the query is received by the engine. There may be a skew from the when the client issued the query due to network latency or server load that may slow the processing of IO work. The timeout will be cancelled if the first result is sent back before the timeout has ended. See the VDBs section for more on setting the query-timeout VDB property. See the Admin Guide for more on modifying the file to set default query timeout for all queries.

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