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Overview
Comment: | Fix some problems with handling IO errors on the experimental branch. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | experimental |
Files: | files | file ages | folders |
SHA1: |
eade8bc238df580412f5cf1b91a91532 |
User & Date: | dan 2010-06-12 12:02:36.000 |
Context
2010-06-14
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07:53 | Add some fault-injection tests to improve coverage. (check-in: 37b26d125f user: dan tags: experimental) | |
2010-06-12
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12:02 | Fix some problems with handling IO errors on the experimental branch. (check-in: eade8bc238 user: dan tags: experimental) | |
2010-06-11
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19:04 | Experimental change to the xShmXXX parts of the VFS interface. (check-in: ca68472db0 user: dan tags: experimental) | |
Changes
Changes to src/test_vfs.c.
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636 637 638 639 640 641 642 | assert(0); return SQLITE_OK; } static void tvfsAllocPage(TestvfsBuffer *p, int iPage, int pgsz){ assert( iPage<TESTVFS_MAX_PAGES ); if( p->aPage[iPage]==0 ){ | | | 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 | assert(0); return SQLITE_OK; } static void tvfsAllocPage(TestvfsBuffer *p, int iPage, int pgsz){ assert( iPage<TESTVFS_MAX_PAGES ); if( p->aPage[iPage]==0 ){ p->aPage[iPage] = (u8 *)ckalloc(pgsz); memset(p->aPage[iPage], 0, pgsz); p->pgsz = pgsz; } } static int tvfsShmPage( sqlite3_file *pFile, /* Handle open on database file */ |
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Changes to src/wal.c.
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447 448 449 450 451 452 453 | return rc; } /* ** Return a pointer to the WalCkptInfo structure in the wal-index. */ static volatile WalCkptInfo *walCkptInfo(Wal *pWal){ | > > > | > > > | | | | 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 | return rc; } /* ** Return a pointer to the WalCkptInfo structure in the wal-index. */ static volatile WalCkptInfo *walCkptInfo(Wal *pWal){ assert( pWal->nWiData>0 && pWal->apWiData[0] ); return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]); } /* ** Return a pointer to the WalIndexHdr structure in the wal-index. */ static volatile WalIndexHdr *walIndexHdr(Wal *pWal){ assert( pWal->nWiData>0 && pWal->apWiData[0] ); return (volatile WalIndexHdr*)pWal->apWiData[0]; } /* ** This structure is used to implement an iterator that loops through ** all frames in the WAL in database page order. Where two or more frames ** correspond to the same database page, the iterator visits only the ** frame most recently written to the WAL (in other words, the frame with |
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545 546 547 548 549 550 551 | /* ** Write the header information in pWal->hdr into the wal-index. ** ** The checksum on pWal->hdr is updated before it is written. */ static void walIndexWriteHdr(Wal *pWal){ | | > | < < | | | 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 | /* ** Write the header information in pWal->hdr into the wal-index. ** ** The checksum on pWal->hdr is updated before it is written. */ static void walIndexWriteHdr(Wal *pWal){ volatile WalIndexHdr *aHdr = walIndexHdr(pWal); const int nCksum = offsetof(WalIndexHdr, aCksum); assert( pWal->writeLock ); pWal->hdr.isInit = 1; walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum); memcpy((void *)&aHdr[1], (void *)&pWal->hdr, sizeof(WalIndexHdr)); sqlite3OsShmBarrier(pWal->pDbFd); memcpy((void *)&aHdr[0], (void *)&pWal->hdr, sizeof(WalIndexHdr)); } /* ** This function encodes a single frame header and writes it to a buffer ** supplied by the caller. A frame-header is made up of a series of ** 4-byte big-endian integers, as follows: ** |
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723 724 725 726 727 728 729 | assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 ); return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1); } static int walNextHash(int iPriorHash){ return (iPriorHash+1)&(HASHTABLE_NSLOT-1); } | > > > > > > > > > > > > > > > | | < | > > > > | > | | | | | | | | | | | | > | > > > > > > > | 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 | assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 ); return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1); } static int walNextHash(int iPriorHash){ return (iPriorHash+1)&(HASHTABLE_NSLOT-1); } /* ** Return pointers to the hash table and page number array stored on ** page iHash of the wal-index. The wal-index is broken into 32KB pages ** numbered starting from 0. ** ** Set output variable *paHash to point to the start of the hash table ** in the wal-index file. Set *piZero to one less than the frame ** number of the first frame indexed by this hash table. If a ** slot in the hash table is set to N, it refers to frame number ** (*piZero+N) in the log. ** ** Finally, set *paPgno such that for all frames F between (*piZero+1) and ** (*piZero+HASHTABLE_NPAGE), (*paPgno)[F] is the database page number ** associated with frame F. */ static int walHashGet( Wal *pWal, /* WAL handle */ int iHash, /* Find the iHash'th table */ volatile HASHTABLE_DATATYPE **paHash, /* OUT: Pointer to hash index */ volatile u32 **paPgno, /* OUT: Pointer to page number array */ u32 *piZero /* OUT: Frame associated with *paPgno[0] */ ){ int rc; /* Return code */ volatile u32 *aPgno; rc = walIndexPage(pWal, iHash, &aPgno); assert( rc==SQLITE_OK || iHash>0 ); if( rc==SQLITE_OK ){ u32 iZero; volatile HASHTABLE_DATATYPE *aHash; aHash = (volatile HASHTABLE_DATATYPE *)&aPgno[HASHTABLE_NPAGE]; if( iHash==0 ){ aPgno = &aPgno[WALINDEX_HDR_SIZE/sizeof(u32)-1]; iZero = 0; }else{ iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE; aPgno = &aPgno[-1*iZero-1]; } *paPgno = aPgno; *paHash = aHash; *piZero = iZero; } return rc; } /* ** Return the number of the wal-index page that contains the hash-table ** and page-number array that contain entries corresponding to WAL frame ** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages ** are numbered starting from 0. */ static int walFramePage(u32 iFrame){ int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE; assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE) && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE) && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)) && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE) && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE)) |
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772 773 774 775 776 777 778 | int iHash = walFramePage(iFrame); if( iHash==0 ){ return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1]; } return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE]; } | < < < < < < < < < < < < < < < < < < < < < < < < < | | > > > > > > > > > > | > | | | | | | | | | | | | < | 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 | int iHash = walFramePage(iFrame); if( iHash==0 ){ return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1]; } return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE]; } /* ** Remove entries from the hash table that point to WAL slots greater ** than pWal->hdr.mxFrame. ** ** This function is called whenever pWal->hdr.mxFrame is decreased due ** to a rollback or savepoint. ** ** At most only the hash table containing pWal->hdr.mxFrame needs to be ** updated. Any later hash tables will be automatically cleared when ** pWal->hdr.mxFrame advances to the point where those hash tables are ** actually needed. */ static void walCleanupHash(Wal *pWal){ volatile HASHTABLE_DATATYPE *aHash; /* Pointer to hash table to clear */ volatile u32 *aPgno; /* Page number array for hash table */ u32 iZero; /* frame == (aHash[x]+iZero) */ int iLimit = 0; /* Zero values greater than this */ int nByte; /* Number of bytes to zero in aPgno[] */ int i; /* Used to iterate through aHash[] */ assert( pWal->writeLock ); testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE-1 ); testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE ); testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE+1 ); if( pWal->hdr.mxFrame==0 ) return; /* Obtain pointers to the hash-table and page-number array containing ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed ** that the page said hash-table and array reside on is already mapped. */ assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) ); assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] ); walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &aHash, &aPgno, &iZero); /* Zero all hash-table entries that correspond to frame numbers greater ** than pWal->hdr.mxFrame. */ iLimit = pWal->hdr.mxFrame - iZero; assert( iLimit>0 ); for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i]>iLimit ){ aHash[i] = 0; } } /* Zero the entries in the aPgno array that correspond to frames with ** frame numbers greater than pWal->hdr.mxFrame. */ nByte = ((char *)aHash - (char *)&aPgno[pWal->hdr.mxFrame+1]); memset((void *)&aPgno[pWal->hdr.mxFrame+1], 0, nByte); #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT /* Verify that the every entry in the mapping region is still reachable ** via the hash table even after the cleanup. */ if( iLimit ){ int i; /* Loop counter */ |
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862 863 864 865 866 867 868 | /* ** Set an entry in the wal-index that will map database page number ** pPage into WAL frame iFrame. */ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){ | | > > > > > | < < | < < < | | < > > > > > < < | | | | | | > | > > | 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 | /* ** Set an entry in the wal-index that will map database page number ** pPage into WAL frame iFrame. */ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){ int rc; /* Return code */ u32 iZero; /* One less than frame number of aPgno[1] */ volatile u32 *aPgno; /* Page number array */ volatile HASHTABLE_DATATYPE *aHash; /* Hash table */ rc = walHashGet(pWal, walFramePage(iFrame), &aHash, &aPgno, &iZero); /* Assuming the wal-index file was successfully mapped, populate the ** page number array and hash table entry. */ if( rc==SQLITE_OK ){ int iKey; /* Hash table key */ int idx; /* Value to write to hash-table slot */ TESTONLY( int nCollide = 0; /* Number of hash collisions */ ) idx = iFrame - iZero; assert( idx <= HASHTABLE_NSLOT/2 + 1 ); /* If this is the first entry to be added to this hash-table, zero the ** entire hash table and aPgno[] array before proceding. */ if( idx==1 ){ int nByte = (u8 *)&aHash[HASHTABLE_NSLOT] - (u8 *)&aPgno[1+iZero]; memset((void*)&aPgno[1+iZero], 0, nByte); } /* If the entry in aPgno[] is already set, then the previous writer ** must have exited unexpectedly in the middle of a transaction (after ** writing one or more dirty pages to the WAL to free up memory). ** Remove the remnants of that writers uncommitted transaction from ** the hash-table before writing any new entries. */ if( aPgno[iFrame] ){ walCleanupHash(pWal); assert( !aPgno[iFrame] ); } /* Write the aPgno[] array entry and the hash-table slot. */ for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){ assert( nCollide++ < idx ); } aPgno[iFrame] = iPage; aHash[iKey] = idx; #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT /* Verify that the number of entries in the hash table exactly equals ** the number of entries in the mapping region. */ { |
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1302 1303 1304 1305 1306 1307 1308 | memset(p, 0, nByte); /* Allocate space for the WalIterator object */ p->nSegment = nSegment; aSpace = (HASHTABLE_DATATYPE *)&p->aSegment[nSegment]; aTmp = &aSpace[HASHTABLE_NPAGE*nSegment]; for(i=0; i<nSegment; i++){ | | > | < < | < | > | | | 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 | memset(p, 0, nByte); /* Allocate space for the WalIterator object */ p->nSegment = nSegment; aSpace = (HASHTABLE_DATATYPE *)&p->aSegment[nSegment]; aTmp = &aSpace[HASHTABLE_NPAGE*nSegment]; for(i=0; i<nSegment; i++){ volatile HASHTABLE_DATATYPE *aHash; int j; u32 iZero; int nEntry; volatile u32 *aPgno; int rc; rc = walHashGet(pWal, i, &aHash, &aPgno, &iZero); if( rc!=SQLITE_OK ){ return rc; } nEntry = ((i+1)==nSegment)?iLast-iZero:(u32 *)aHash-(u32 *)&aPgno[iZero+1]; iZero++; aPgno += iZero; for(j=0; j<nEntry; j++){ aSpace[j] = j; } walMergesort((u32 *)aPgno, aTmp, aSpace, &nEntry); |
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1387 1388 1389 1390 1391 1392 1393 | int rc; /* Return code */ int szPage = pWal->hdr.szPage; /* Database page-size */ WalIterator *pIter = 0; /* Wal iterator context */ u32 iDbpage = 0; /* Next database page to write */ u32 iFrame = 0; /* Wal frame containing data for iDbpage */ u32 mxSafeFrame; /* Max frame that can be backfilled */ int i; /* Loop counter */ | < < < | 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 | int rc; /* Return code */ int szPage = pWal->hdr.szPage; /* Database page-size */ WalIterator *pIter = 0; /* Wal iterator context */ u32 iDbpage = 0; /* Next database page to write */ u32 iFrame = 0; /* Wal frame containing data for iDbpage */ u32 mxSafeFrame; /* Max frame that can be backfilled */ int i; /* Loop counter */ volatile WalCkptInfo *pInfo; /* The checkpoint status information */ /* Allocate the iterator */ rc = walIteratorInit(pWal, &pIter); if( rc!=SQLITE_OK || pWal->hdr.mxFrame==0 ){ goto walcheckpoint_out; } /*** TODO: Move this test out to the caller. Make it an assert() here ***/ if( pWal->hdr.szPage!=nBuf ){ rc = SQLITE_CORRUPT_BKPT; goto walcheckpoint_out; } /* Compute in mxSafeFrame the index of the last frame of the WAL that is ** safe to write into the database. Frames beyond mxSafeFrame might ** overwrite database pages that are in use by active readers and thus ** cannot be backfilled from the WAL. */ mxSafeFrame = pWal->hdr.mxFrame; pInfo = walCkptInfo(pWal); for(i=1; i<WAL_NREADER; i++){ u32 y = pInfo->aReadMark[i]; if( mxSafeFrame>=y ){ assert( y<=pWal->hdr.mxFrame ); rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1); if( rc==SQLITE_OK ){ pInfo->aReadMark[i] = READMARK_NOT_USED; |
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1451 1452 1453 1454 1455 1456 1457 | if( rc!=SQLITE_OK ) break; rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, (iDbpage-1)*szPage); if( rc!=SQLITE_OK ) break; } /* If work was actually accomplished... */ if( rc==SQLITE_OK ){ | | | 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 | if( rc!=SQLITE_OK ) break; rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, (iDbpage-1)*szPage); if( rc!=SQLITE_OK ) break; } /* If work was actually accomplished... */ if( rc==SQLITE_OK ){ if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){ rc = sqlite3OsTruncate(pWal->pDbFd, ((i64)pWal->hdr.nPage*(i64)szPage)); if( rc==SQLITE_OK && sync_flags ){ rc = sqlite3OsSync(pWal->pDbFd, sync_flags); } } if( rc==SQLITE_OK ){ pInfo->nBackfill = mxSafeFrame; |
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1536 1537 1538 1539 1540 1541 1542 | ** pWal->hdr, then pWal->hdr is updated to the content of the new header ** and *pChanged is set to 1. ** ** If the checksum cannot be verified return non-zero. If the header ** is read successfully and the checksum verified, return zero. */ int walIndexTryHdr(Wal *pWal, int *pChanged){ | | | | < < < | < < < > | | | | 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 | ** pWal->hdr, then pWal->hdr is updated to the content of the new header ** and *pChanged is set to 1. ** ** If the checksum cannot be verified return non-zero. If the header ** is read successfully and the checksum verified, return zero. */ int walIndexTryHdr(Wal *pWal, int *pChanged){ u32 aCksum[2]; /* Checksum on the header content */ WalIndexHdr h1, h2; /* Two copies of the header content */ WalIndexHdr volatile *aHdr; /* Header in shared memory */ /* The first page of the wal-index must be mapped at this point. */ assert( pWal->nWiData>0 && pWal->apWiData[0] ); /* Read the header. This might happen currently with a write to the ** same area of shared memory on a different CPU in a SMP, ** meaning it is possible that an inconsistent snapshot is read ** from the file. If this happens, return non-zero. ** ** There are two copies of the header at the beginning of the wal-index. ** When reading, read [0] first then [1]. Writes are in the reverse order. ** Memory barriers are used to prevent the compiler or the hardware from ** reordering the reads and writes. */ aHdr = walIndexHdr(pWal); memcpy(&h1, (void *)&aHdr[0], sizeof(h1)); sqlite3OsShmBarrier(pWal->pDbFd); memcpy(&h2, (void *)&aHdr[1], sizeof(h2)); if( memcmp(&h1, &h2, sizeof(h1))!=0 ){ return 1; /* Dirty read */ } if( h1.isInit==0 ){ return 1; /* Malformed header - probably all zeros */ } |
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1605 1606 1607 1608 1609 1610 1611 | ** ** If the wal-index header is successfully read, return SQLITE_OK. ** Otherwise an SQLite error code. */ static int walIndexReadHdr(Wal *pWal, int *pChanged){ int rc; /* Return code */ int badHdr; /* True if a header read failed */ | | > > > | | > > | > | | < | < | > < < > > | 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 | ** ** If the wal-index header is successfully read, return SQLITE_OK. ** Otherwise an SQLite error code. */ static int walIndexReadHdr(Wal *pWal, int *pChanged){ int rc; /* Return code */ int badHdr; /* True if a header read failed */ volatile u32 *page0; /* Ensure that page 0 of the wal-index (the page that contains the ** wal-index header) is mapped. Return early if an error occurs here. */ assert( pChanged ); rc = walIndexPage(pWal, 0, &page0); if( rc!=SQLITE_OK ){ return rc; }; assert( page0 || pWal->writeLock==0 ); /* If the first page of the wal-index has been mapped, try to read the ** wal-index header immediately, without holding any lock. This usually ** works, but may fail if the wal-index header is corrupt or currently ** being modified by another user. */ badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1); /* If the first attempt failed, it might have been due to a race ** with a writer. So get a WRITE lock and try again. */ assert( badHdr==0 || pWal->writeLock==0 ); if( badHdr && SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){ pWal->writeLock = 1; if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){ badHdr = walIndexTryHdr(pWal, pChanged); if( badHdr ){ /* If the wal-index header is still malformed even while holding ** a WRITE lock, it can only mean that the header is corrupted and ** needs to be reconstructed. So run recovery to do exactly that. */ rc = walIndexRecover(pWal); *pChanged = 1; } } pWal->writeLock = 0; walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1); } return rc; } /* ** This is the value that walTryBeginRead returns when it needs to |
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1678 1679 1680 1681 1682 1683 1684 | ** to select a particular WAL_READ_LOCK() that strives to let the ** checkpoint process do as much work as possible. This routine might ** update values of the aReadMark[] array in the header, but if it does ** so it takes care to hold an exclusive lock on the corresponding ** WAL_READ_LOCK() while changing values. */ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ | < | 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 | ** to select a particular WAL_READ_LOCK() that strives to let the ** checkpoint process do as much work as possible. This routine might ** update values of the aReadMark[] array in the header, but if it does ** so it takes care to hold an exclusive lock on the corresponding ** WAL_READ_LOCK() while changing values. */ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ volatile WalCkptInfo *pInfo; /* Checkpoint information in wal-index */ u32 mxReadMark; /* Largest aReadMark[] value */ int mxI; /* Index of largest aReadMark[] value */ int i; /* Loop counter */ int rc = SQLITE_OK; /* Return code */ assert( pWal->readLock<0 ); /* Not currently locked */ |
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1717 1718 1719 1720 1721 1722 1723 | } } } if( rc!=SQLITE_OK ){ return rc; } | < < | | 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 | } } } if( rc!=SQLITE_OK ){ return rc; } pInfo = walCkptInfo(pWal); if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){ /* The WAL has been completely backfilled (or it is empty). ** and can be safely ignored. */ rc = walLockShared(pWal, WAL_READ_LOCK(0)); sqlite3OsShmBarrier(pWal->pDbFd); if( rc==SQLITE_OK ){ if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){ /* It is not safe to allow the reader to continue here if frames ** may have been appended to the log before READ_LOCK(0) was obtained. ** When holding READ_LOCK(0), the reader ignores the entire log file, ** which implies that the database file contains a trustworthy ** snapshoT. Since holding READ_LOCK(0) prevents a checkpoint from ** happening, this is usually correct. ** |
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1821 1822 1823 1824 1825 1826 1827 | ** date before proceeding. That would not be possible without somehow ** blocking writers. It only guarantees that a dangerous checkpoint or ** log-wrap (either of which would require an exclusive lock on ** WAL_READ_LOCK(mxI)) has not occurred since the snapshot was valid. */ sqlite3OsShmBarrier(pWal->pDbFd); if( pInfo->aReadMark[mxI]!=mxReadMark | | | 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 | ** date before proceeding. That would not be possible without somehow ** blocking writers. It only guarantees that a dangerous checkpoint or ** log-wrap (either of which would require an exclusive lock on ** WAL_READ_LOCK(mxI)) has not occurred since the snapshot was valid. */ sqlite3OsShmBarrier(pWal->pDbFd); if( pInfo->aReadMark[mxI]!=mxReadMark || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){ walUnlockShared(pWal, WAL_READ_LOCK(mxI)); return WAL_RETRY; }else{ assert( mxReadMark<=pWal->hdr.mxFrame ); pWal->readLock = mxI; } |
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1931 1932 1933 1934 1935 1936 1937 1938 | ** table after the current read-transaction had started. */ for(iHash=walFramePage(iLast); iHash>=0 && iRead==0; iHash--){ volatile HASHTABLE_DATATYPE *aHash; /* Pointer to hash table */ volatile u32 *aPgno; /* Pointer to array of page numbers */ u32 iZero; /* Frame number corresponding to aPgno[0] */ int iKey; /* Hash slot index */ | > | > > > | 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 | ** table after the current read-transaction had started. */ for(iHash=walFramePage(iLast); iHash>=0 && iRead==0; iHash--){ volatile HASHTABLE_DATATYPE *aHash; /* Pointer to hash table */ volatile u32 *aPgno; /* Pointer to array of page numbers */ u32 iZero; /* Frame number corresponding to aPgno[0] */ int iKey; /* Hash slot index */ int rc; rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero); if( rc!=SQLITE_OK ){ return rc; } for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){ u32 iFrame = aHash[iKey] + iZero; if( iFrame<=iLast && aPgno[iFrame]==pgno ){ assert( iFrame>iRead ); iRead = iFrame; } } |
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1997 1998 1999 2000 2001 2002 2003 | ** thread to write as doing so would cause a fork. So this routine ** returns SQLITE_BUSY in that case and no write transaction is started. ** ** There can only be a single writer active at a time. */ int sqlite3WalBeginWriteTransaction(Wal *pWal){ int rc; | < < | | 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 | ** thread to write as doing so would cause a fork. So this routine ** returns SQLITE_BUSY in that case and no write transaction is started. ** ** There can only be a single writer active at a time. */ int sqlite3WalBeginWriteTransaction(Wal *pWal){ int rc; /* Cannot start a write transaction without first holding a read ** transaction. */ assert( pWal->readLock>=0 ); /* Only one writer allowed at a time. Get the write lock. Return ** SQLITE_BUSY if unable. */ rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1); if( rc ){ return rc; } pWal->writeLock = 1; /* If another connection has written to the database file since the ** time the read transaction on this connection was started, then ** the write is disallowed. */ if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){ walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1); pWal->writeLock = 0; rc = SQLITE_BUSY; } return rc; } |
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