So, if I am already using an old version before 3.11 and enable the mmap, the data may lost after os crash. It’s that right?
原始邮件 发件人:Richard [email protected] 收件人:SQLite mailing [email protected] 发送时间:2016年11月3日(周四) 21:21 主题:Re: [sqlite] Is msync necessary for SQLite? On 11/3/16, sanhua.zh [email protected] wrote: Here is a part of code in [unixWrite]. (os_unix.h) Is not it written by mmap ? You are looking at older code that is not longer used. Look at latest sources and you will see that the code you quote below is enclosed within #if defined(SQLITE_MMAP_READWRITE) ... #endif So writing to mmapped memory only happens if you compile with the (undocumented, unsupported, and untested) -DSQLITE_MMAP_READWRITE option. #if SQLITE_MAX_MMAP_SIZE0 /* Deal with as much of this write request as possible by transfering ** data from the memory mapping using memcpy(). */ if( offsetpFile-mmapSize ){ if( offset+amt = pFile-mmapSize ){ int size = -1; struct stat buf; /* Used to hold return values of fstat() */ if( !osFstat(pFile-h, buf) ){ size = (int)buf.st_size; } memcpy(((u8 *)(pFile-pMapRegion))[offset], pBuf, amt); return SQLITE_OK; }else{ int nCopy = (int)(pFile-mmapSize - offset); memcpy(((u8 *)(pFile-pMapRegion))[offset], pBuf, nCopy); pBuf = ((u8 *)pBuf)[nCopy]; amt -= nCopy; offset += nCopy; } } #endif 原始邮件 发件人:Richard [email protected] 收件人:SQLite mailing [email protected] 发送时间:2016年11月3日(周四) 17:49 主题:Re: [sqlite] Is msync necessary for SQLite? On 11/3/16, sanhua.zh [email protected] wrote: I run in iOS. The mmap is enable in recent version. So, once a mmap enable, data may lost after os crash unless msync. But I can’t find anywhere in the source of SQLite call the msync. Is it a bug? No. Mmap() is only used for reading, not writing. All changes are implemented by calling write() and fsync(). -- D. Richard Hipp [email protected] _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users -- D. Richard Hipp [email protected] _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
