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Improved header comment with better instructions on the vfslog.c

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extension.

FossilOrigin-Name: 4bd592c8f0e011e203443a6e88008a61d6926df5
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drh
2013-10-19 16:51:39 +00:00
parent 197bc20c48
commit 05684271c6
3 changed files with 38 additions and 15 deletions
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37
ext/misc/vfslog.c
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@ -16,14 +16,37 @@
/*
** This module contains code for a wrapper VFS that causes a log of
** most VFS calls to be written into a file on disk. The log
** is stored as comma-separated variables.
** most VFS calls to be written into a file on disk.
**
** All calls on sqlite3_file objects are logged.
** Additionally, calls to the xAccess(), xOpen(), and xDelete()
** methods are logged. The other sqlite3_vfs object methods (xDlXXX,
** xRandomness, xSleep, xCurrentTime, xGetLastError and xCurrentTimeInt64)
** are not logged.
** Each database connection creates a separate log file in the same
** directory as the original database and named after the original
** database. A unique suffix is added to avoid name collisions.
** Separate log files are used so that concurrent processes do not
** try to write log operations to the same file at the same instant,
** resulting in overwritten or comingled log text.
**
** Each individual log file records operations by a single database
** connection on both the original database and its associated rollback
** journal.
**
** The log files are in the comma-separated-value (CSV) format. The
** log files can be imported into an SQLite database using the ".import"
** command of the SQLite command-line shell for analysis.
**
** One technique for using this module is to append the text of this
** module to the end of a standard "sqlite3.c" amalgamation file then
** add the following compile-time options:
**
** -DSQLITE_EXTRA_INIT=sqlite3_register_vfslog
** -DSQLITE_USE_FCNTL_TRACE
**
** The first compile-time option causes the sqlite3_register_vfslog()
** function, defined below, to be invoked when SQLite is initialized.
** That causes this custom VFS to become the default VFS for all
** subsequent connections. The SQLITE_USE_FCNTL_TRACE option causes
** the SQLite core to issue extra sqlite3_file_control() operations
** with SQLITE_FCNTL_TRACE to give some indication of what is going
** on in the core.
*/
#include "sqlite3.h"