blob: d34e3cf9f4a7090f9ca11e35c4c963b999ee0b32 [file] [log] [blame]
/*
** 2007 May 1
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used to implement incremental BLOB I/O.
*/
#include "sqliteInt.h"
#include "vdbeInt.h"
#ifndef SQLITE_OMIT_INCRBLOB
/*
** Valid sqlite3_blob* handles point to Incrblob structures.
*/
typedef struct Incrblob Incrblob;
struct Incrblob {
int nByte; /* Size of open blob, in bytes */
int iOffset; /* Byte offset of blob in cursor data */
u16 iCol; /* Table column this handle is open on */
BtCursor *pCsr; /* Cursor pointing at blob row */
sqlite3_stmt *pStmt; /* Statement holding cursor open */
sqlite3 *db; /* The associated database */
char *zDb; /* Database name */
Table *pTab; /* Table object */
};
/*
** This function is used by both blob_open() and blob_reopen(). It seeks
** the b-tree cursor associated with blob handle p to point to row iRow.
** If successful, SQLITE_OK is returned and subsequent calls to
** sqlite3_blob_read() or sqlite3_blob_write() access the specified row.
**
** If an error occurs, or if the specified row does not exist or does not
** contain a value of type TEXT or BLOB in the column nominated when the
** blob handle was opened, then an error code is returned and *pzErr may
** be set to point to a buffer containing an error message. It is the
** responsibility of the caller to free the error message buffer using
** sqlite3DbFree().
**
** If an error does occur, then the b-tree cursor is closed. All subsequent
** calls to sqlite3_blob_read(), blob_write() or blob_reopen() will
** immediately return SQLITE_ABORT.
*/
static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
int rc; /* Error code */
char *zErr = 0; /* Error message */
Vdbe *v = (Vdbe *)p->pStmt;
/* Set the value of register r[1] in the SQL statement to integer iRow.
** This is done directly as a performance optimization
*/
v->aMem[1].flags = MEM_Int;
v->aMem[1].u.i = iRow;
/* If the statement has been run before (and is paused at the OP_ResultRow)
** then back it up to the point where it does the OP_NotExists. This could
** have been down with an extra OP_Goto, but simply setting the program
** counter is faster. */
if( v->pc>4 ){
v->pc = 4;
assert( v->aOp[v->pc].opcode==OP_NotExists );
rc = sqlite3VdbeExec(v);
}else{
rc = sqlite3_step(p->pStmt);
}
if( rc==SQLITE_ROW ){
VdbeCursor *pC = v->apCsr[0];
u32 type = pC->nHdrParsed>p->iCol ? pC->aType[p->iCol] : 0;
testcase( pC->nHdrParsed==p->iCol );
testcase( pC->nHdrParsed==p->iCol+1 );
if( type<12 ){
zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
type==0?"null": type==7?"real": "integer"
);
rc = SQLITE_ERROR;
sqlite3_finalize(p->pStmt);
p->pStmt = 0;
}else{
p->iOffset = pC->aType[p->iCol + pC->nField];
p->nByte = sqlite3VdbeSerialTypeLen(type);
p->pCsr = pC->uc.pCursor;
sqlite3BtreeIncrblobCursor(p->pCsr);
}
}
if( rc==SQLITE_ROW ){
rc = SQLITE_OK;
}else if( p->pStmt ){
rc = sqlite3_finalize(p->pStmt);
p->pStmt = 0;
if( rc==SQLITE_OK ){
zErr = sqlite3MPrintf(p->db, "no such rowid: %lld", iRow);
rc = SQLITE_ERROR;
}else{
zErr = sqlite3MPrintf(p->db, "%s", sqlite3_errmsg(p->db));
}
}
assert( rc!=SQLITE_OK || zErr==0 );
assert( rc!=SQLITE_ROW && rc!=SQLITE_DONE );
*pzErr = zErr;
return rc;
}
/*
** Open a blob handle.
*/
int sqlite3_blob_open(
sqlite3* db, /* The database connection */
const char *zDb, /* The attached database containing the blob */
const char *zTable, /* The table containing the blob */
const char *zColumn, /* The column containing the blob */
sqlite_int64 iRow, /* The row containing the glob */
int wrFlag, /* True -> read/write access, false -> read-only */
sqlite3_blob **ppBlob /* Handle for accessing the blob returned here */
){
int nAttempt = 0;
int iCol; /* Index of zColumn in row-record */
int rc = SQLITE_OK;
char *zErr = 0;
Table *pTab;
Incrblob *pBlob = 0;
Parse sParse;
#ifdef SQLITE_ENABLE_API_ARMOR
if( ppBlob==0 ){
return SQLITE_MISUSE_BKPT;
}
#endif
*ppBlob = 0;
#ifdef SQLITE_ENABLE_API_ARMOR
if( !sqlite3SafetyCheckOk(db) || zTable==0 ){
return SQLITE_MISUSE_BKPT;
}
#endif
wrFlag = !!wrFlag; /* wrFlag = (wrFlag ? 1 : 0); */
sqlite3_mutex_enter(db->mutex);
pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
do {
memset(&sParse, 0, sizeof(Parse));
if( !pBlob ) goto blob_open_out;
sParse.db = db;
sqlite3DbFree(db, zErr);
zErr = 0;
sqlite3BtreeEnterAll(db);
pTab = sqlite3LocateTable(&sParse, 0, zTable, zDb);
if( pTab && IsVirtual(pTab) ){
pTab = 0;
sqlite3ErrorMsg(&sParse, "cannot open virtual table: %s", zTable);
}
if( pTab && !HasRowid(pTab) ){
pTab = 0;
sqlite3ErrorMsg(&sParse, "cannot open table without rowid: %s", zTable);
}
#ifndef SQLITE_OMIT_VIEW
if( pTab && pTab->pSelect ){
pTab = 0;
sqlite3ErrorMsg(&sParse, "cannot open view: %s", zTable);
}
#endif
if( !pTab ){
if( sParse.zErrMsg ){
sqlite3DbFree(db, zErr);
zErr = sParse.zErrMsg;
sParse.zErrMsg = 0;
}
rc = SQLITE_ERROR;
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
pBlob->pTab = pTab;
pBlob->zDb = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zDbSName;
/* Now search pTab for the exact column. */
for(iCol=0; iCol<pTab->nCol; iCol++) {
if( sqlite3StrICmp(pTab->aCol[iCol].zName, zColumn)==0 ){
break;
}
}
if( iCol==pTab->nCol ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, "no such column: \"%s\"", zColumn);
rc = SQLITE_ERROR;
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
/* If the value is being opened for writing, check that the
** column is not indexed, and that it is not part of a foreign key.
*/
if( wrFlag ){
const char *zFault = 0;
Index *pIdx;
#ifndef SQLITE_OMIT_FOREIGN_KEY
if( db->flags&SQLITE_ForeignKeys ){
/* Check that the column is not part of an FK child key definition. It
** is not necessary to check if it is part of a parent key, as parent
** key columns must be indexed. The check below will pick up this
** case. */
FKey *pFKey;
for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
int j;
for(j=0; j<pFKey->nCol; j++){
if( pFKey->aCol[j].iFrom==iCol ){
zFault = "foreign key";
}
}
}
}
#endif
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
int j;
for(j=0; j<pIdx->nKeyCol; j++){
/* FIXME: Be smarter about indexes that use expressions */
if( pIdx->aiColumn[j]==iCol || pIdx->aiColumn[j]==XN_EXPR ){
zFault = "indexed";
}
}
}
if( zFault ){
sqlite3DbFree(db, zErr);
zErr = sqlite3MPrintf(db, "cannot open %s column for writing", zFault);
rc = SQLITE_ERROR;
sqlite3BtreeLeaveAll(db);
goto blob_open_out;
}
}
pBlob->pStmt = (sqlite3_stmt *)sqlite3VdbeCreate(&sParse);
assert( pBlob->pStmt || db->mallocFailed );
if( pBlob->pStmt ){
/* This VDBE program seeks a btree cursor to the identified
** db/table/row entry. The reason for using a vdbe program instead
** of writing code to use the b-tree layer directly is that the
** vdbe program will take advantage of the various transaction,
** locking and error handling infrastructure built into the vdbe.
**
** After seeking the cursor, the vdbe executes an OP_ResultRow.
** Code external to the Vdbe then "borrows" the b-tree cursor and
** uses it to implement the blob_read(), blob_write() and
** blob_bytes() functions.
**
** The sqlite3_blob_close() function finalizes the vdbe program,
** which closes the b-tree cursor and (possibly) commits the
** transaction.
*/
static const int iLn = VDBE_OFFSET_LINENO(2);
static const VdbeOpList openBlob[] = {
{OP_TableLock, 0, 0, 0}, /* 0: Acquire a read or write lock */
{OP_OpenRead, 0, 0, 0}, /* 1: Open a cursor */
/* blobSeekToRow() will initialize r[1] to the desired rowid */
{OP_NotExists, 0, 5, 1}, /* 2: Seek the cursor to rowid=r[1] */
{OP_Column, 0, 0, 1}, /* 3 */
{OP_ResultRow, 1, 0, 0}, /* 4 */
{OP_Halt, 0, 0, 0}, /* 5 */
};
Vdbe *v = (Vdbe *)pBlob->pStmt;
int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
VdbeOp *aOp;
sqlite3VdbeAddOp4Int(v, OP_Transaction, iDb, wrFlag,
pTab->pSchema->schema_cookie,
pTab->pSchema->iGeneration);
sqlite3VdbeChangeP5(v, 1);
assert( sqlite3VdbeCurrentAddr(v)==2 || db->mallocFailed );
aOp = sqlite3VdbeAddOpList(v, ArraySize(openBlob), openBlob, iLn);
/* Make sure a mutex is held on the table to be accessed */
sqlite3VdbeUsesBtree(v, iDb);
if( db->mallocFailed==0 ){
assert( aOp!=0 );
/* Configure the OP_TableLock instruction */
#ifdef SQLITE_OMIT_SHARED_CACHE
aOp[0].opcode = OP_Noop;
#else
aOp[0].p1 = iDb;
aOp[0].p2 = pTab->tnum;
aOp[0].p3 = wrFlag;
sqlite3VdbeChangeP4(v, 2, pTab->zName, P4_TRANSIENT);
}
if( db->mallocFailed==0 ){
#endif
/* Remove either the OP_OpenWrite or OpenRead. Set the P2
** parameter of the other to pTab->tnum. */
if( wrFlag ) aOp[1].opcode = OP_OpenWrite;
aOp[1].p2 = pTab->tnum;
aOp[1].p3 = iDb;
/* Configure the number of columns. Configure the cursor to
** think that the table has one more column than it really
** does. An OP_Column to retrieve this imaginary column will
** always return an SQL NULL. This is useful because it means
** we can invoke OP_Column to fill in the vdbe cursors type
** and offset cache without causing any IO.
*/
aOp[1].p4type = P4_INT32;
aOp[1].p4.i = pTab->nCol+1;
aOp[3].p2 = pTab->nCol;
sParse.nVar = 0;
sParse.nMem = 1;
sParse.nTab = 1;
sqlite3VdbeMakeReady(v, &sParse);
}
}
pBlob->iCol = iCol;
pBlob->db = db;
sqlite3BtreeLeaveAll(db);
if( db->mallocFailed ){
goto blob_open_out;
}
rc = blobSeekToRow(pBlob, iRow, &zErr);
} while( (++nAttempt)<SQLITE_MAX_SCHEMA_RETRY && rc==SQLITE_SCHEMA );
blob_open_out:
if( rc==SQLITE_OK && db->mallocFailed==0 ){
*ppBlob = (sqlite3_blob *)pBlob;
}else{
if( pBlob && pBlob->pStmt ) sqlite3VdbeFinalize((Vdbe *)pBlob->pStmt);
sqlite3DbFree(db, pBlob);
}
sqlite3ErrorWithMsg(db, rc, (zErr ? "%s" : 0), zErr);
sqlite3DbFree(db, zErr);
sqlite3ParserReset(&sParse);
rc = sqlite3ApiExit(db, rc);
sqlite3_mutex_leave(db->mutex);
return rc;
}
/*
** Close a blob handle that was previously created using
** sqlite3_blob_open().
*/
int sqlite3_blob_close(sqlite3_blob *pBlob){
Incrblob *p = (Incrblob *)pBlob;
int rc;
sqlite3 *db;
if( p ){
sqlite3_stmt *pStmt = p->pStmt;
db = p->db;
sqlite3_mutex_enter(db->mutex);
sqlite3DbFree(db, p);
sqlite3_mutex_leave(db->mutex);
rc = sqlite3_finalize(pStmt);
}else{
rc = SQLITE_OK;
}
return rc;
}
/*
** Perform a read or write operation on a blob
*/
static int blobReadWrite(
sqlite3_blob *pBlob,
void *z,
int n,
int iOffset,
int (*xCall)(BtCursor*, u32, u32, void*)
){
int rc;
Incrblob *p = (Incrblob *)pBlob;
Vdbe *v;
sqlite3 *db;
if( p==0 ) return SQLITE_MISUSE_BKPT;
db = p->db;
sqlite3_mutex_enter(db->mutex);
v = (Vdbe*)p->pStmt;
if( n<0 || iOffset<0 || ((sqlite3_int64)iOffset+n)>p->nByte ){
/* Request is out of range. Return a transient error. */
rc = SQLITE_ERROR;
}else if( v==0 ){
/* If there is no statement handle, then the blob-handle has
** already been invalidated. Return SQLITE_ABORT in this case.
*/
rc = SQLITE_ABORT;
}else{
/* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
** returned, clean-up the statement handle.
*/
assert( db == v->db );
sqlite3BtreeEnterCursor(p->pCsr);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
if( xCall==sqlite3BtreePutData && db->xPreUpdateCallback ){
/* If a pre-update hook is registered and this is a write cursor,
** invoke it here.
**
** TODO: The preupdate-hook is passed SQLITE_DELETE, even though this
** operation should really be an SQLITE_UPDATE. This is probably
** incorrect, but is convenient because at this point the new.* values
** are not easily obtainable. And for the sessions module, an
** SQLITE_UPDATE where the PK columns do not change is handled in the
** same way as an SQLITE_DELETE (the SQLITE_DELETE code is actually
** slightly more efficient). Since you cannot write to a PK column
** using the incremental-blob API, this works. For the sessions module
** anyhow.
*/
sqlite3_int64 iKey;
iKey = sqlite3BtreeIntegerKey(p->pCsr);
sqlite3VdbePreUpdateHook(
v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
);
}
#endif
rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
sqlite3BtreeLeaveCursor(p->pCsr);
if( rc==SQLITE_ABORT ){
sqlite3VdbeFinalize(v);
p->pStmt = 0;
}else{
v->rc = rc;
}
}
sqlite3Error(db, rc);
rc = sqlite3ApiExit(db, rc);
sqlite3_mutex_leave(db->mutex);
return rc;
}
/*
** Read data from a blob handle.
*/
int sqlite3_blob_read(sqlite3_blob *pBlob, void *z, int n, int iOffset){
return blobReadWrite(pBlob, z, n, iOffset, sqlite3BtreePayloadChecked);
}
/*
** Write data to a blob handle.
*/
int sqlite3_blob_write(sqlite3_blob *pBlob, const void *z, int n, int iOffset){
return blobReadWrite(pBlob, (void *)z, n, iOffset, sqlite3BtreePutData);
}
/*
** Query a blob handle for the size of the data.
**
** The Incrblob.nByte field is fixed for the lifetime of the Incrblob
** so no mutex is required for access.
*/
int sqlite3_blob_bytes(sqlite3_blob *pBlob){
Incrblob *p = (Incrblob *)pBlob;
return (p && p->pStmt) ? p->nByte : 0;
}
/*
** Move an existing blob handle to point to a different row of the same
** database table.
**
** If an error occurs, or if the specified row does not exist or does not
** contain a blob or text value, then an error code is returned and the
** database handle error code and message set. If this happens, then all
** subsequent calls to sqlite3_blob_xxx() functions (except blob_close())
** immediately return SQLITE_ABORT.
*/
int sqlite3_blob_reopen(sqlite3_blob *pBlob, sqlite3_int64 iRow){
int rc;
Incrblob *p = (Incrblob *)pBlob;
sqlite3 *db;
if( p==0 ) return SQLITE_MISUSE_BKPT;
db = p->db;
sqlite3_mutex_enter(db->mutex);
if( p->pStmt==0 ){
/* If there is no statement handle, then the blob-handle has
** already been invalidated. Return SQLITE_ABORT in this case.
*/
rc = SQLITE_ABORT;
}else{
char *zErr;
rc = blobSeekToRow(p, iRow, &zErr);
if( rc!=SQLITE_OK ){
sqlite3ErrorWithMsg(db, rc, (zErr ? "%s" : 0), zErr);
sqlite3DbFree(db, zErr);
}
assert( rc!=SQLITE_SCHEMA );
}
rc = sqlite3ApiExit(db, rc);
assert( rc==SQLITE_OK || p->pStmt==0 );
sqlite3_mutex_leave(db->mutex);
return rc;
}
#endif /* #ifndef SQLITE_OMIT_INCRBLOB */