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JetGetThreadStats Function

Windows

Last modified: January 09, 2012

Applies to: Windows | Windows Server

The JetGetThreadStats function retrieves performance information from the database engine for the current thread. Multiple calls can be used to collect statistics that reflect the activity of the database engine on this thread between those calls.

Windows Vista:  JetGetThreadStats is introduced in Windows Vista.

JET_ERR JET_API JetGetThreadStats(
  __out         void* pvResult,
  __in          unsigned long cbMax
);

Parameters

pvResult

The output buffer which receives the thread statistics data. The buffer contains a JET_THREADSTATS structure after a successful call.

cbMax

The maximum size in bytes of the output buffer.

Return Value

This function returns the JET_ERR datatype with one of the following return codes. For more information about the possible ESE errors, see Extensible Storage Engine Errors and Error Handling Parameters.

Return code

Description

JET_errSuccess

The operation completed successfully.

JET_errBufferTooSmall

The operation failed because the provided output buffer was too small to contain the requested data. The JetGetThreadStats function will return this error when the output buffer is too small to contain the smallest version of the JET_THREADSTATS structure supported by the database engine.

On success, the output buffer will contain a JET_THREADSTATS structure that contains database engine statistics for the current thread.

On failure, the state of the output buffer is undefined.

Remarks

The information provided by two consecutive calls of this API are intended to be used to compute the expense of any other database engine operations on the current thread. Generally, this is done by taking a before and after reading of the statistics and subtracting the after count from the before count to get the net count of operations performed.

For example, an application could call JetGetThreadStats once to get an initial reading of the statistics for the current thread. It could then call the JetMove function with the cRow parameter set to JET_MoveNext to move to the next index entry on an index. It could then call JetGetThreadStats again to get another reading of the thread's statistics. It could then subtract the cPageReferenced counter from the second reading from the first. The result would be the number of database pages referenced by the database engine to perform the JetMove operation.

The statistics for each thread are accumulated for the lifetime of that thread. The statistics are reset if the database engine's DLL is unloaded from the host process.

The JET_THREADSTATS structure will likely be expanded in the future to contain more statistics. New statistics will be added to the end of the structure and can be retrieved with an increased output buffer size. The presence of additional statistics can be inferred by a larger cbStruct value.

Requirements

Client

Requires Windows Vista.

Server

Requires Windows Server 2008.

Header

Declared in Esent.h.

Library

Use ESENT.lib.

DLL

Requires ESENT.dll.

See Also

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