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In cases where a readonly_shm client cannot take the DMS lock on the *-shm

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file, have it parse the wal file and create a wal-index to access it in heap
memory.

FossilOrigin-Name: 18b268433d739486eac1b04947bd418655e4bc56e8dc63ffa558aa4552a32e30
This commit is contained in:
dan
2017-11-04 18:10:03 +00:00
parent 44c8a97e01
commit 11caf4f4b7
5 changed files with 192 additions and 31 deletions
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16
manifest
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@@ -1,5 +1,5 @@
C Fix\stest\scases\sin\swal2.test\sbroken\sby\sthe\slocking\schange\sin\sthe\sprevious\ncommit.
D 2017-11-02T18:57:46.036
C In\scases\swhere\sa\sreadonly_shm\sclient\scannot\stake\sthe\sDMS\slock\son\sthe\s*-shm\nfile,\shave\sit\sparse\sthe\swal\sfile\sand\screate\sa\swal-index\sto\saccess\sit\sin\sheap\nmemory.
D 2017-11-04T18:10:03.528
F Makefile.in 5bae3f2f3d42f2ad52b141562d74872c97ac0fca6c54953c91bb150a0e6427a8
F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
F Makefile.msc 3a5cb477ec3ce5274663b693164e349db63348667cd45bad78cc13d580b691e2
@@ -543,7 +543,7 @@ F src/vdbesort.c 731a09e5cb9e96b70c394c1b7cf3860fbe84acca7682e178615eb941a3a0ef2
F src/vdbetrace.c 48e11ebe040c6b41d146abed2602e3d00d621d7ebe4eb29b0a0f1617fd3c2f6c
F src/vtab.c 0e4885495172e1bdf54b12cce23b395ac74ef5729031f15e1bc1e3e6b360ed1a
F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
F src/wal.c 38480e7bdc697cf88a13a22ffe60f7bd761bc02b45f7a323f1bb9e61a136b3ae
F src/wal.c 2b287b5250e89d548c6bbd1d204d0db41046bb3984b9b4a79fc84e22359f1beb
F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
F src/walker.c d591e8a9ccf60abb010966b354fcea4aa08eba4d83675c2b281a8764c76cc22f
F src/where.c b7a075f5fb3d912a891dcc3257f538372bb4a1622dd8ca7d752ad95ce8949ba4
@@ -1526,8 +1526,8 @@ F test/walnoshm.test 84ca10c544632a756467336b7c3b864d493ee496
F test/waloverwrite.test dad2f26567f1b45174e54fbf9a8dc1cb876a7f03
F test/walpersist.test 8c6b7e3ec1ba91b5e4dc4e0921d6d3f87cd356a6
F test/walprotocol.test 0b92feb132ccebd855494d917d3f6c2d717ace20
F test/walro.test e492598baa8cd7777fef6203f6fe922c20cd691cc19e60ccd0dd0dbc68394d0a
F test/walro2.test 23fea1e7abae13072b0640ef846d32080b2fc435658d4c4eb9db266b07b33776
F test/walro.test 906586c3ae7a991d8c840ceed92400aee21a0a3e4155ce7c4220399777311552
F test/walro2.test 611ceebd190edeca9bf39e5068cbc864f15294371b4acf9ee837db477840af54
F test/walshared.test 0befc811dcf0b287efae21612304d15576e35417
F test/walslow.test c05c68d4dc2700a982f89133ce103a1a84cc285f
F test/walthread.test de8dbaf6d9e41481c460ba31ca61e163d7348f8e
@@ -1668,7 +1668,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
P 5190d84a296b7cf716ef43bf7b6d4d351ef1a4d650de37dc01a5ab333da7c05d
R 30693e487c23aaa3c080ebb269e4e38f
P f569c3517234881f9425075aab65a32ffd0deb8e793f421a241d8cca881da33f
R 10fc0a1645ce290a2a283e11360fe887
U dan
Z a5242a9fca30f5b5641106b18cdb01ae
Z 79ea7f3203670e23f752126d91be88fd

2
manifest.uuid
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@@ -1 +1 @@
f569c3517234881f9425075aab65a32ffd0deb8e793f421a241d8cca881da33f
18b268433d739486eac1b04947bd418655e4bc56e8dc63ffa558aa4552a32e30

176
src/wal.c
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@@ -455,6 +455,7 @@ struct Wal {
u8 truncateOnCommit; /* True to truncate WAL file on commit */
u8 syncHeader; /* Fsync the WAL header if true */
u8 padToSectorBoundary; /* Pad transactions out to the next sector */
u8 bUnlocked;
WalIndexHdr hdr; /* Wal-index header for current transaction */
u32 minFrame; /* Ignore wal frames before this one */
u32 iReCksum; /* On commit, recalculate checksums from here */
@@ -1270,13 +1271,14 @@ recovery_error:
** Close an open wal-index.
*/
static void walIndexClose(Wal *pWal, int isDelete){
if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE || pWal->bUnlocked ){
int i;
for(i=0; i<pWal->nWiData; i++){
sqlite3_free((void *)pWal->apWiData[i]);
pWal->apWiData[i] = 0;
}
}else{
}
if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
}
}
@@ -2091,15 +2093,13 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
*/
assert( pChanged );
rc = walIndexPage(pWal, 0, &page0);
if( rc==SQLITE_READONLY_CANTLOCK ){
assert( page0==0 && pWal->writeLock==0 );
pWal->bUnlocked = 1;
pWal->exclusiveMode = WAL_HEAPMEMORY_MODE;
*pChanged = 1;
}else
if( rc!=SQLITE_OK ){
if( rc==SQLITE_READONLY_CANTLOCK
#ifdef SQLITE_ENABLE_SNAPSHOT
&& pWal->pSnapshot==0
#endif
){
memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
rc = SQLITE_OK;
}
return rc;
};
assert( page0 || pWal->writeLock==0 );
@@ -2116,7 +2116,7 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
*/
assert( badHdr==0 || pWal->writeLock==0 );
if( badHdr ){
if( pWal->readOnly & WAL_SHM_RDONLY ){
if( pWal->bUnlocked==0 && (pWal->readOnly & WAL_SHM_RDONLY) ){
if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
walUnlockShared(pWal, WAL_WRITE_LOCK);
rc = SQLITE_READONLY_RECOVERY;
@@ -2146,6 +2146,12 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
if( badHdr==0 && pWal->hdr.iVersion!=WALINDEX_MAX_VERSION ){
rc = SQLITE_CANTOPEN_BKPT;
}
if( pWal->bUnlocked ){
if( rc!=SQLITE_OK ){
walIndexClose(pWal, 0);
}
pWal->exclusiveMode = WAL_NORMAL_MODE;
}
return rc;
}
@@ -2156,6 +2162,144 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
*/
#define WAL_RETRY (-1)
/*
** Open an "unlocked" transaction. An unlocked transaction is a read
** transaction used by a read-only client in cases where the *-shm
** file cannot be mapped and its contents cannot be trusted. It is
** assumed that the *-wal file has been read and that a wal-index
** constructed in heap memory is currently available in Wal.apWiData[].
**
** If this function returns SQLITE_OK, then the read transaction has
** been successfully opened. In this case output variable (*pChanged)
** is set to true before returning if the caller should discard the
** contents of the page cache before proceeding. Or, if it returns
** WAL_RETRY, then the heap memory wal-index has been discarded and
** the caller should retry opening the read transaction from the
** beginning (including attempting to map the *-shm file).
**
** If an error occurs, an SQLite error code is returned.
*/
static int walBeginUnlocked(Wal *pWal, int *pChanged){
i64 szWal; /* Size of wal file on disk in bytes */
i64 iOffset; /* Current offset when reading wal file */
u8 aBuf[WAL_HDRSIZE]; /* Buffer to load WAL header into */
u8 *aFrame = 0; /* Malloc'd buffer to load entire frame */
int szFrame; /* Number of bytes in buffer aFrame[] */
u8 *aData; /* Pointer to data part of aFrame buffer */
volatile void *pDummy; /* Dummy argument for xShmMap */
int rc; /* Return code */
u32 aSaveCksum[2]; /* Saved copy of pWal->hdr.aFrameCksum */
assert( pWal->bUnlocked );
assert( pWal->readOnly & WAL_SHM_RDONLY );
assert( pWal->nWiData>0 && pWal->apWiData[0] );
/* Take WAL_READ_LOCK(0). This has the effect of preventing any
** live clients from running a checkpoint, but does not stop them
** from running recovery. */
rc = walLockShared(pWal, WAL_READ_LOCK(0));
if( rc!=SQLITE_OK ){
return (rc==SQLITE_BUSY ? WAL_RETRY : rc);
}
pWal->readLock = 0;
/* Try to map the *-shm file again. If it succeeds this time, then
** a non-readonly_shm connection has already connected to the database.
** In this case, start over with opening the transaction.
**
** The WAL_READ_LOCK(0) lock held by this client prevents a checkpoint
** from taking place. But it does not prevent the wal from being wrapped
** if a checkpoint has already taken place. This means that if another
** client is connected at this point, it may have already checkpointed
** the entire wal. In that case it would not be safe to continue with
** the unlocked transaction, as the other client may overwrite wal
** frames that this client is still using. */
rc = sqlite3OsShmMap(pWal->pDbFd, 0, WALINDEX_PGSZ, 0, &pDummy);
if( rc!=SQLITE_READONLY_CANTLOCK ){
assert( rc!=SQLITE_OK );
rc = (rc==SQLITE_READONLY ? WAL_RETRY : rc);
goto begin_unlocked_out;
}
memcpy(&pWal->hdr, (void*)walIndexHdr(pWal), sizeof(WalIndexHdr));
rc = sqlite3OsFileSize(pWal->pWalFd, &szWal);
if( rc!=SQLITE_OK || (szWal<WAL_HDRSIZE && pWal->hdr.mxFrame==0) ){
/* If the wal file is too small to contain a wal-header and the
** wal-index header has mxFrame==0, then it must be safe to proceed
** reading the database file only. However, the page cache cannot
** be trusted, as a read/write connection may have connected, written
** the db, run a checkpoint, truncated the wal file and disconnected
** since this client's last read transaction. */
*pChanged = 1;
goto begin_unlocked_out;
}
/* Check the salt keys at the start of the wal file still match. */
rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
if( rc!=SQLITE_OK ){
goto begin_unlocked_out;
}
if( memcmp(&pWal->hdr.aSalt, &aBuf[16], 8) ){
rc = WAL_RETRY;
goto begin_unlocked_out;
}
/* Allocate a buffer to read frames into */
szFrame = pWal->hdr.szPage + WAL_FRAME_HDRSIZE;
aFrame = (u8 *)sqlite3_malloc64(szFrame);
if( aFrame==0 ){
rc = SQLITE_NOMEM_BKPT;
goto begin_unlocked_out;
}
aData = &aFrame[WAL_FRAME_HDRSIZE];
aSaveCksum[0] = pWal->hdr.aFrameCksum[0];
aSaveCksum[1] = pWal->hdr.aFrameCksum[1];
for(iOffset=walFrameOffset(pWal->hdr.mxFrame+1, pWal->hdr.szPage);
iOffset+szFrame<=szWal;
iOffset+=szFrame
){
u32 pgno; /* Database page number for frame */
u32 nTruncate; /* dbsize field from frame header */
/* Read and decode the next log frame. */
rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_IOERR_SHORT_READ ){
/* If this branch is taken, some other client has truncated the
** *-wal file since the call to sqlite3OsFileSize() above. This
** indicates that a read-write client has connected to the system.
** So retry opening this read transaction. */
rc = WAL_RETRY;
}
break;
}
if( !walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame) ) break;
/* If nTruncate is non-zero, this is a commit record. */
if( nTruncate ){
rc = WAL_RETRY;
break;
}
}
pWal->hdr.aFrameCksum[0] = aSaveCksum[0];
pWal->hdr.aFrameCksum[1] = aSaveCksum[1];
begin_unlocked_out:
sqlite3_free(aFrame);
if( rc!=SQLITE_OK ){
int i;
for(i=0; i<pWal->nWiData; i++){
sqlite3_free((void*)pWal->apWiData[i]);
pWal->apWiData[i] = 0;
}
pWal->bUnlocked = 0;
sqlite3WalEndReadTransaction(pWal);
*pChanged = 1;
}
return rc;
}
/*
** Attempt to start a read transaction. This might fail due to a race or
** other transient condition. When that happens, it returns WAL_RETRY to
@@ -2244,7 +2388,10 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
}
if( !useWal ){
rc = walIndexReadHdr(pWal, pChanged);
assert( rc==SQLITE_OK );
if( pWal->bUnlocked==0 ){
rc = walIndexReadHdr(pWal, pChanged);
}
if( rc==SQLITE_BUSY ){
/* If there is not a recovery running in another thread or process
** then convert BUSY errors to WAL_RETRY. If recovery is known to
@@ -2273,6 +2420,9 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
if( rc!=SQLITE_OK ){
return rc;
}
else if( pWal->bUnlocked ){
return walBeginUnlocked(pWal, pChanged);
}
}
assert( pWal->nWiData>0 );
@@ -2626,7 +2776,7 @@ int sqlite3WalFindFrame(
** then the WAL is ignored by the reader so return early, as if the
** WAL were empty.
*/
if( iLast==0 || pWal->readLock==0 ){
if( iLast==0 || (pWal->readLock==0 && pWal->bUnlocked==0) ){
*piRead = 0;
return SQLITE_OK;
}

10
test/walro.test
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@@ -105,7 +105,7 @@ do_multiclient_test tn {
do_test 1.2.2 {
code1 { sqlite3 db file:test.db?readonly_shm=1 }
list [catch { sql1 { SELECT * FROM t1 } } msg] $msg
} {1 {unable to open database file}}
} {0 {a b c d e f g h i j}}
do_test 1.2.3 {
code1 { db close }
@@ -114,10 +114,10 @@ do_multiclient_test tn {
file attributes test.db-shm -permissions r--r--r--
code1 { sqlite3 db file:test.db?readonly_shm=1 }
csql1 { SELECT * FROM t1 }
} {1 {unable to open database file}}
} {0 {a b c d e f g h i j}}
do_test 1.2.4 {
code1 { sqlite3_extended_errcode db }
} {SQLITE_CANTOPEN}
} {SQLITE_OK}
do_test 1.2.5 {
file attributes test.db-shm -permissions rw-r--r--
@@ -162,10 +162,10 @@ do_multiclient_test tn {
file attributes test.db-shm -permissions r--r--r--
code1 { sqlite3 db file:test.db?readonly_shm=1 }
csql1 { SELECT * FROM t1 }
} {1 {unable to open database file}}
} {0 {a b c d e f g h i j k l}}
do_test 1.3.2.4 {
code1 { sqlite3_extended_errcode db }
} {SQLITE_CANTOPEN}
} {SQLITE_OK}
#-----------------------------------------------------------------------
# Test cases 1.4.* check that checkpoints and log wraps don't prevent

19
test/walro2.test
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@@ -62,7 +62,7 @@ do_multiclient_test tn {
file exists test.db-shm
} {1}
do_test 1.2 {
do_test 1.2.1 {
forcecopy test.db test.db2
forcecopy test.db-wal test.db2-wal
forcecopy test.db-shm test.db2-shm
@@ -71,7 +71,10 @@ do_multiclient_test tn {
}
sql1 { SELECT * FROM t1 }
} {}
} {a b c d}
do_test 1.2.2 {
sql1 { SELECT * FROM t1 }
} {a b c d}
do_test 1.3.1 {
code3 { sqlite3 db3 test.db2 }
@@ -106,13 +109,21 @@ do_multiclient_test tn {
BEGIN;
SELECT * FROM t1;
}
} {a b c d}
} {a b c d e f g h}
do_test 2.3.1 {
code3 { sqlite3 db3 test.db2 }
sql3 { SELECT * FROM t1 }
} {a b c d e f g h}
do_test 2.3.2 {
sql3 { INSERT INTO t1 VALUES('i', 'j') }
code3 { db3 close }
sql1 { COMMIT }
} {}
breakpoint
do_test 2.3.3 {
sql1 { SELECT * FROM t1 }
} {a b c d e f g h i j}
}
finish_test