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Add the sqlite3_snapshot_recover() interface and related functionality.

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FossilOrigin-Name: b70c85ce6d07b08e13f4ea99edb8f4855a6d7580
This commit is contained in:
drh
2016-11-26 19:44:40 +00:00
parent 6412a4c8a5 4b4ffadb43
commit dd5fa17d3c
12 changed files with 1036 additions and 400 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/main.c
+41 -8
View File
@@ -3981,7 +3981,6 @@ int sqlite3_snapshot_get(
){
int rc = SQLITE_ERROR;
#ifndef SQLITE_OMIT_WAL
int iDb;
#ifdef SQLITE_ENABLE_API_ARMOR
if( !sqlite3SafetyCheckOk(db) ){
@@ -3990,13 +3989,15 @@ int sqlite3_snapshot_get(
#endif
sqlite3_mutex_enter(db->mutex);
iDb = sqlite3FindDbName(db, zDb);
if( iDb==0 || iDb>1 ){
Btree *pBt = db->aDb[iDb].pBt;
if( 0==sqlite3BtreeIsInTrans(pBt) ){
rc = sqlite3BtreeBeginTrans(pBt, 0);
if( rc==SQLITE_OK ){
rc = sqlite3PagerSnapshotGet(sqlite3BtreePager(pBt), ppSnapshot);
if( db->autoCommit==0 ){
int iDb = sqlite3FindDbName(db, zDb);
if( iDb==0 || iDb>1 ){
Btree *pBt = db->aDb[iDb].pBt;
if( 0==sqlite3BtreeIsInTrans(pBt) ){
rc = sqlite3BtreeBeginTrans(pBt, 0);
if( rc==SQLITE_OK ){
rc = sqlite3PagerSnapshotGet(sqlite3BtreePager(pBt), ppSnapshot);
}
}
}
}
@@ -4043,6 +4044,38 @@ int sqlite3_snapshot_open(
return rc;
}
/*
** Recover as many snapshots as possible from the wal file associated with
** schema zDb of database db.
*/
int sqlite3_snapshot_recover(sqlite3 *db, const char *zDb){
int rc = SQLITE_ERROR;
int iDb;
#ifndef SQLITE_OMIT_WAL
#ifdef SQLITE_ENABLE_API_ARMOR
if( !sqlite3SafetyCheckOk(db) ){
return SQLITE_MISUSE_BKPT;
}
#endif
sqlite3_mutex_enter(db->mutex);
iDb = sqlite3FindDbName(db, zDb);
if( iDb==0 || iDb>1 ){
Btree *pBt = db->aDb[iDb].pBt;
if( 0==sqlite3BtreeIsInReadTrans(pBt) ){
rc = sqlite3BtreeBeginTrans(pBt, 0);
if( rc==SQLITE_OK ){
rc = sqlite3PagerSnapshotRecover(sqlite3BtreePager(pBt));
sqlite3BtreeCommit(pBt);
}
}
}
sqlite3_mutex_leave(db->mutex);
#endif /* SQLITE_OMIT_WAL */
return rc;
}
/*
** Free a snapshot handle obtained from sqlite3_snapshot_get().
*/
src/pager.c
+14
View File
@@ -7405,6 +7405,20 @@ int sqlite3PagerSnapshotOpen(Pager *pPager, sqlite3_snapshot *pSnapshot){
}
return rc;
}
/*
** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this
** is not a WAL database, return an error.
*/
int sqlite3PagerSnapshotRecover(Pager *pPager){
int rc;
if( pPager->pWal ){
rc = sqlite3WalSnapshotRecover(pPager->pWal);
}else{
rc = SQLITE_ERROR;
}
return rc;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#endif /* !SQLITE_OMIT_WAL */
src/pager.h
+1
View File
@@ -182,6 +182,7 @@ int sqlite3PagerSharedLock(Pager *pPager);
# ifdef SQLITE_ENABLE_SNAPSHOT
int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot);
int sqlite3PagerSnapshotOpen(Pager *pPager, sqlite3_snapshot *pSnapshot);
int sqlite3PagerSnapshotRecover(Pager *pPager);
# endif
#else
# define sqlite3PagerUseWal(x) 0
src/sqlite.h.in
+51 -4
View File
@@ -8287,7 +8287,9 @@ int sqlite3_system_errno(sqlite3*);
** to an historical snapshot (if possible). The destructor for
** sqlite3_snapshot objects is [sqlite3_snapshot_free()].
*/
typedef struct sqlite3_snapshot sqlite3_snapshot;
typedef struct sqlite3_snapshot {
unsigned char hidden[48];
} sqlite3_snapshot;
/*
** CAPI3REF: Record A Database Snapshot
@@ -8298,9 +8300,32 @@ typedef struct sqlite3_snapshot sqlite3_snapshot;
** schema S in database connection D. ^On success, the
** [sqlite3_snapshot_get(D,S,P)] interface writes a pointer to the newly
** created [sqlite3_snapshot] object into *P and returns SQLITE_OK.
** ^If schema S of [database connection] D is not a [WAL mode] database
** that is in a read transaction, then [sqlite3_snapshot_get(D,S,P)]
** leaves the *P value unchanged and returns an appropriate [error code].
** If there is not already a read-transaction open on schema S when
** this function is called, one is opened automatically.
**
** The following must be true for this function to succeed. If any of
** the following statements are false when sqlite3_snapshot_get() is
** called, SQLITE_ERROR is returned. The final value of *P is undefined
** in this case.
**
** <ul>
** <li> The database handle must be in [autocommit mode].
**
** <li> Schema S of [database connection] D must be a [WAL mode] database.
**
** <li> There must not be a write transaction open on schema S of database
** connection D.
**
** <li> One or more transactions must have been written to the current wal
** file since it was created on disk (by any connection). This means
** that a snapshot cannot be taken on a wal mode database with no wal
** file immediately after it is first opened. At least one transaction
** must be written to it first.
** </ul>
**
** This function may also return SQLITE_NOMEM. If it is called with the
** database handle in autocommit mode but fails for some other reason,
** whether or not a read transaction is opened on schema S is undefined.
**
** The [sqlite3_snapshot] object returned from a successful call to
** [sqlite3_snapshot_get()] must be freed using [sqlite3_snapshot_free()]
@@ -8393,6 +8418,28 @@ SQLITE_EXPERIMENTAL int sqlite3_snapshot_cmp(
sqlite3_snapshot *p2
);
/*
** CAPI3REF: Recover snapshots from a wal file
** EXPERIMENTAL
**
** If all connections disconnect from a database file but do not perform
** a checkpoint, the existing wal file is opened along with the database
** file the next time the database is opened. At this point it is only
** possible to successfully call sqlite3_snapshot_open() to open the most
** recent snapshot of the database (the one at the head of the wal file),
** even though the wal file may contain other valid snapshots for which
** clients have sqlite3_snapshot handles.
**
** This function attempts to scan the wal file associated with database zDb
** of database handle db and make all valid snapshots available to
** sqlite3_snapshot_open(). It is an error if there is already a read
** transaction open on the database, or if the database is not a wal mode
** database.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
SQLITE_EXPERIMENTAL int sqlite3_snapshot_recover(sqlite3 *db, const char *zDb);
/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
src/test1.c
+143
View File
@@ -2310,6 +2310,38 @@ static int SQLITE_TCLAPI test_snapshot_get(
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_recover DB DBNAME
*/
static int SQLITE_TCLAPI test_snapshot_recover(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
int rc;
sqlite3 *db;
char *zName;
if( objc!=3 ){
Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
return TCL_ERROR;
}
if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
zName = Tcl_GetString(objv[2]);
rc = sqlite3_snapshot_recover(db, zName);
if( rc!=SQLITE_OK ){
Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
return TCL_ERROR;
}else{
Tcl_ResetResult(interp);
}
return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_open DB DBNAME SNAPSHOT
@@ -2388,6 +2420,113 @@ static int SQLITE_TCLAPI test_snapshot_cmp(
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_get_blob DB DBNAME
*/
static int SQLITE_TCLAPI test_snapshot_get_blob(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
int rc;
sqlite3 *db;
char *zName;
sqlite3_snapshot *pSnapshot = 0;
if( objc!=3 ){
Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME");
return TCL_ERROR;
}
if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
zName = Tcl_GetString(objv[2]);
rc = sqlite3_snapshot_get(db, zName, &pSnapshot);
if( rc!=SQLITE_OK ){
Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
return TCL_ERROR;
}else{
Tcl_SetObjResult(interp,
Tcl_NewByteArrayObj((unsigned char*)pSnapshot, sizeof(sqlite3_snapshot))
);
sqlite3_snapshot_free(pSnapshot);
}
return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_open_blob DB DBNAME SNAPSHOT
*/
static int SQLITE_TCLAPI test_snapshot_open_blob(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
int rc;
sqlite3 *db;
char *zName;
unsigned char *pBlob;
int nBlob;
if( objc!=4 ){
Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SNAPSHOT");
return TCL_ERROR;
}
if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
zName = Tcl_GetString(objv[2]);
pBlob = Tcl_GetByteArrayFromObj(objv[3], &nBlob);
if( nBlob!=sizeof(sqlite3_snapshot) ){
Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
return TCL_ERROR;
}
rc = sqlite3_snapshot_open(db, zName, (sqlite3_snapshot*)pBlob);
if( rc!=SQLITE_OK ){
Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
return TCL_ERROR;
}
return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Usage: sqlite3_snapshot_cmp_blob SNAPSHOT1 SNAPSHOT2
*/
static int SQLITE_TCLAPI test_snapshot_cmp_blob(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
int res;
unsigned char *p1;
unsigned char *p2;
int n1;
int n2;
if( objc!=3 ){
Tcl_WrongNumArgs(interp, 1, objv, "SNAPSHOT1 SNAPSHOT2");
return TCL_ERROR;
}
p1 = Tcl_GetByteArrayFromObj(objv[1], &n1);
p2 = Tcl_GetByteArrayFromObj(objv[2], &n2);
if( n1!=sizeof(sqlite3_snapshot) || n1!=n2 ){
Tcl_AppendResult(interp, "bad SNAPSHOT", 0);
return TCL_ERROR;
}
res = sqlite3_snapshot_cmp((sqlite3_snapshot*)p1, (sqlite3_snapshot*)p2);
Tcl_SetObjResult(interp, Tcl_NewIntObj(res));
return TCL_OK;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
/*
** Usage: sqlite3_delete_database FILENAME
*/
@@ -7539,6 +7678,10 @@ int Sqlitetest1_Init(Tcl_Interp *interp){
{ "sqlite3_snapshot_open", test_snapshot_open, 0 },
{ "sqlite3_snapshot_free", test_snapshot_free, 0 },
{ "sqlite3_snapshot_cmp", test_snapshot_cmp, 0 },
{ "sqlite3_snapshot_recover", test_snapshot_recover, 0 },
{ "sqlite3_snapshot_get_blob", test_snapshot_get_blob, 0 },
{ "sqlite3_snapshot_open_blob", test_snapshot_open_blob, 0 },
{ "sqlite3_snapshot_cmp_blob", test_snapshot_cmp_blob, 0 },
#endif
{ "sqlite3_delete_database", test_delete_database, 0 },
};
src/wal.c
+88 -1
View File
@@ -2379,6 +2379,84 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
return rc;
}
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** Attempt to reduce the value of the WalCkptInfo.nBackfillAttempted
** variable so that older snapshots can be accessed. To do this, loop
** through all wal frames from nBackfillAttempted to (nBackfill+1),
** comparing their content to the corresponding page with the database
** file, if any. Set nBackfillAttempted to the frame number of the
** first frame for which the wal file content matches the db file.
**
** This is only really safe if the file-system is such that any page
** writes made by earlier checkpointers were atomic operations, which
** is not always true. It is also possible that nBackfillAttempted
** may be left set to a value larger than expected, if a wal frame
** contains content that duplicate of an earlier version of the same
** page.
**
** SQLITE_OK is returned if successful, or an SQLite error code if an
** error occurs. It is not an error if nBackfillAttempted cannot be
** decreased at all.
*/
int sqlite3WalSnapshotRecover(Wal *pWal){
int rc;
assert( pWal->readLock>=0 );
rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
if( rc==SQLITE_OK ){
volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
int szPage = (int)pWal->szPage;
i64 szDb; /* Size of db file in bytes */
rc = sqlite3OsFileSize(pWal->pDbFd, &szDb);
if( rc==SQLITE_OK ){
void *pBuf1 = sqlite3_malloc(szPage);
void *pBuf2 = sqlite3_malloc(szPage);
if( pBuf1==0 || pBuf2==0 ){
rc = SQLITE_NOMEM;
}else{
u32 i = pInfo->nBackfillAttempted;
for(i=pInfo->nBackfillAttempted; i>pInfo->nBackfill; i--){
volatile ht_slot *dummy;
volatile u32 *aPgno; /* Array of page numbers */
u32 iZero; /* Frame corresponding to aPgno[0] */
u32 pgno; /* Page number in db file */
i64 iDbOff; /* Offset of db file entry */
i64 iWalOff; /* Offset of wal file entry */
rc = walHashGet(pWal, walFramePage(i), &dummy, &aPgno, &iZero);
if( rc!=SQLITE_OK ) break;
pgno = aPgno[i-iZero];
iDbOff = (i64)(pgno-1) * szPage;
if( iDbOff+szPage<=szDb ){
iWalOff = walFrameOffset(i, szPage) + WAL_FRAME_HDRSIZE;
rc = sqlite3OsRead(pWal->pWalFd, pBuf1, szPage, iWalOff);
if( rc==SQLITE_OK ){
rc = sqlite3OsRead(pWal->pDbFd, pBuf2, szPage, iDbOff);
}
if( rc!=SQLITE_OK || 0==memcmp(pBuf1, pBuf2, szPage) ){
break;
}
}
pInfo->nBackfillAttempted = i-1;
}
}
sqlite3_free(pBuf1);
sqlite3_free(pBuf2);
}
walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
}
return rc;
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
/*
** Begin a read transaction on the database.
**
@@ -2441,7 +2519,11 @@ int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
** has not yet set the pInfo->nBackfillAttempted variable to indicate
** its intent. To avoid the race condition this leads to, ensure that
** there is no checkpointer process by taking a shared CKPT lock
** before checking pInfo->nBackfillAttempted. */
** before checking pInfo->nBackfillAttempted.
**
** TODO: Does the aReadMark[] lock prevent a checkpointer from doing
** this already?
*/
rc = walLockShared(pWal, WAL_CKPT_LOCK);
if( rc==SQLITE_OK ){
@@ -3393,9 +3475,14 @@ int sqlite3WalHeapMemory(Wal *pWal){
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
int rc = SQLITE_OK;
WalIndexHdr *pRet;
static const u32 aZero[4] = { 0, 0, 0, 0 };
assert( pWal->readLock>=0 && pWal->writeLock==0 );
if( memcmp(&pWal->hdr.aFrameCksum[0],aZero,16)==0 ){
*ppSnapshot = 0;
return SQLITE_ERROR;
}
pRet = (WalIndexHdr*)sqlite3_malloc(sizeof(WalIndexHdr));
if( pRet==0 ){
rc = SQLITE_NOMEM_BKPT;
src/wal.h
+1
View File
@@ -131,6 +131,7 @@ int sqlite3WalHeapMemory(Wal *pWal);
#ifdef SQLITE_ENABLE_SNAPSHOT
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot);
void sqlite3WalSnapshotOpen(Wal *pWal, sqlite3_snapshot *pSnapshot);
int sqlite3WalSnapshotRecover(Wal *pWal);
#endif
#ifdef SQLITE_ENABLE_ZIPVFS