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CSQLiteStmt.ProgressHandlermethod

The **ProgressHandler** method causes a callback function to be invoked periodically during long running calls to **Step_** and **GetRow** for a database connection.

DatabasesmethodCSQLite.incdoc-orphan

No implementation located. This member is documented, but the source scan found no matching declaration. It is likely declared in a header this scan does not resolve, or provided by a macro.

Syntax

SUB ProgressHandler (BYVAL nOps AS LONG, BYVAL pCallback AS ANY PTR, BYVAL pArg AS ANY PTR)

Parameters

Name		Description
`nOps`		Number of virtual machine instructions that are evaluated between successive invocations of the callback.
`pCallback`		Pointer to the callback function.
`pArg`		Data that is passed through as the only parameter to the callback function.
`op`		An integer constant, taken from the set of SQLITE_DBSTATUS options, that determines the parameter to interrogate.
`pCurrent`		The current value of the requested parameter.
`pHighwater`		The highest instantaneous value.
`resetFlag`		TRUE or FALSE. If true, then the highest instantaneous value is reset back down to the current value.

Return value

The number of bytes freed.

SQLITE_OK (0) on success and a non-zero error code on failure.

Description

The ProgressHandler method causes a callback function to be invoked periodically during long running calls to Step_ and GetRow for a database connection. An example use for this interface is to keep a GUI updated during a large query.

Callback function prototype:

Remarks

Only a single progress handler may be defined at one time per database connection; setting a new progress handler cancels the old one. Setting parameter pCallBack to NULL disables the progress handler. The progress handler is also disabled by setting pCallBack to a value less than 1.

If the progress callback returns non-zero, the operation is interrupted. This feature can be used to implement a "Cancel" button on a GUI progress dialog box.

The progress handler callback must not do anything that will modify the database connection that invoked the progress handler. Note that Prepare and Step_ both modify their database connections for the meaning of "modify" in this paragraph.

Example

SQLITE_DBSTATUS_LOOKASIDE_USED = 0 SQLITE_DBSTATUS_CACHE_USED = 1 SQLITE_DBSTATUS_SCHEMA_USED = 2 SQLITE_DBSTATUS_STMT_USED = 3 SQLITE_DBSTATUS_LOOKASIDE_HIT = 4 SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE = 5 SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL = 6 SQLITE_DBSTATUS_CACHE_HIT = 7 SQLITE_DBSTATUS_CACHE_MISS = 8 SQLITE_DBSTATUS_CACHE_WRITE = 9

Reference

Include file CSQLite.inc
Documented in Databases/CSQLite Class.md
Topic: CSQLite Class