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5e3a475a87
http://www.qtcentre.org/threads/36131-Attempting-to-use-Sqlite-backup-api-from-driver-handle-fails on a post by chemmalion that allows one to save a memory sqlite3 database to file. This is really neat because now the strain on the hardrive is gone! This version loads the database on startup and saves it every 3 minutes to disk. The database is saved upon closing the program as well.
81 lines
3.8 KiB
C++
81 lines
3.8 KiB
C++
#include "sqlite3_util.h"
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#include <sqlite3.h>
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#include <QVariant>
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#include <QSqlDriver>
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/*
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** This function is used to load the contents of a database file on disk
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** into the "main" database of open database connection pInMemory, or
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** to save the current contents of the database opened by pInMemory into
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** a database file on disk. pInMemory is probably an in-memory database,
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** but this function will also work fine if it is not.
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**
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** Parameter zFilename points to a nul-terminated string containing the
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** name of the database file on disk to load from or save to. If parameter
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** isSave is non-zero, then the contents of the file zFilename are
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** overwritten with the contents of the database opened by pInMemory. If
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** parameter isSave is zero, then the contents of the database opened by
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** pInMemory are replaced by data loaded from the file zFilename.
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**
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** If the operation is successful, SQLITE_OK is returned. Otherwise, if
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** an error occurs, an SQLite error code is returned.
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*/
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bool sqlite3_util::sqliteDBMemFile( QSqlDatabase memdb, QString filename, bool save )
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{
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bool state = false;
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QVariant v = memdb.driver()->handle();
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if( v.isValid() && qstrcmp(v.typeName(),"sqlite3*") == 0 )
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{
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// v.data() returns a pointer to the handle
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sqlite3 * handle = *static_cast<sqlite3 **>(v.data());
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if( handle != 0 ) // check that it is not NULL
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{
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sqlite3 * pInMemory = handle;
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const char * zFilename = filename.toLocal8Bit().data();
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int rc; /* Function return code */
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sqlite3 *pFile; /* Database connection opened on zFilename */
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sqlite3_backup *pBackup; /* Backup object used to copy data */
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sqlite3 *pTo; /* Database to copy to (pFile or pInMemory) */
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sqlite3 *pFrom; /* Database to copy from (pFile or pInMemory) */
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/* Open the database file identified by zFilename. Exit early if this fails
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** for any reason. */
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rc = sqlite3_open( zFilename, &pFile );
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if( rc==SQLITE_OK ){
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/* If this is a 'load' operation (isSave==0), then data is copied
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** from the database file just opened to database pInMemory.
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** Otherwise, if this is a 'save' operation (isSave==1), then data
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** is copied from pInMemory to pFile. Set the variables pFrom and
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** pTo accordingly. */
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pFrom = ( save ? pInMemory : pFile);
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pTo = ( save ? pFile : pInMemory);
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/* Set up the backup procedure to copy from the "main" database of
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** connection pFile to the main database of connection pInMemory.
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** If something goes wrong, pBackup will be set to NULL and an error
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** code and message left in connection pTo.
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**
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** If the backup object is successfully created, call backup_step()
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** to copy data from pFile to pInMemory. Then call backup_finish()
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** to release resources associated with the pBackup object. If an
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** error occurred, then an error code and message will be left in
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** connection pTo. If no error occurred, then the error code belonging
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** to pTo is set to SQLITE_OK.
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*/
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pBackup = sqlite3_backup_init(pTo, "main", pFrom, "main");
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if( pBackup ){
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(void)sqlite3_backup_step(pBackup, -1);
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(void)sqlite3_backup_finish(pBackup);
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}
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rc = sqlite3_errcode(pTo);
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}
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/* Close the database connection opened on database file zFilename
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** and return the result of this function. */
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(void)sqlite3_close(pFile);
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if( rc == SQLITE_OK ) state = true;
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}
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}
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return state;
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}
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