third_party/sqlite_google/src/btree.c - Issue 924: sqlite3 pragma get/set user_version implemented

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Issue 924: sqlite3 pragma get/set user_version implemented (Closed) SVN Base: http://google-gears.googlecode.com/svn/contrib/dimitri.glazkov/database2/gears/

Patch Set: moved code to btree.c, restructured Created 3 months, 2 weeks ago

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1 /*	1 /*

2 ** 2004 April 6	2 ** 2004 April 6

3 **	3 **

4 ** The author disclaims copyright to this source code. In place of	4 ** The author disclaims copyright to this source code. In place of

5 ** a legal notice, here is a blessing:	5 ** a legal notice, here is a blessing:

6 **	6 **

7 ** May you do good and not evil.	7 ** May you do good and not evil.

8 ** May you find forgiveness for yourself and forgive others.	8 ** May you find forgiveness for yourself and forgive others.

9 ** May you share freely, never taking more than you give.	9 ** May you share freely, never taking more than you give.

10 **	10 **

11 *************************************************************************	11 *************************************************************************

12 ** $Id: btree.c,v 1.388 2007/05/24 09:20:16 danielk1977 Exp $	12 ** $Id: btree.c,v 1.388 2007/05/24 09:20:16 danielk1977 Exp $

13 **	13 **

14 ** This file implements a external (disk-based) database using BTrees.	14 ** This file implements a external (disk-based) database using BTrees.

15 ** See the header comment on "btreeInt.h" for additional information.	15 ** See the header comment on "btreeInt.h" for additional information.

16 ** Including a description of file format and an overview of operation.	16 ** Including a description of file format and an overview of operation.

17 */	17 */

18 #include "btreeInt.h"	18 #include "btreeInt.h"

19	19

20 /*	20 /*

21 ** The header string that appears at the beginning of every	21 ** The header string that appears at the beginning of every

22 ** SQLite database.	22 ** SQLite database.

23 */	23 */

24 static const char zMagicHeader[] = SQLITE_FILE_HEADER;	24 static const char zMagicHeader[] = SQLITE_FILE_HEADER;

25	25

26 /*	26 /*

27 ** The header string that appears at the beginning of a SQLite	27 ** The header string that appears at the beginning of a SQLite

28 ** database which has been poisoned.	28 ** database which has been poisoned.

29 */	29 */

30 static const char zPoisonHeader[] = "SQLite poison 3";	30 static const char zPoisonHeader[] = "SQLite poison 3";

31	31

	32 /*

	33 ** The user cookie position in the database meta information

	34 ** (see prepare.c#215), incremented by one, because first position is actually

	35 ** the number of free pages in Btree (see vdbe.c#2521)

	36 */

	37 static const int kUserCookie = 6;

32	38

33 /*	39 /*

34 ** Set this global variable to 1 to enable tracing using the TRACE	40 ** Set this global variable to 1 to enable tracing using the TRACE

35 ** macro.	41 ** macro.

36 */	42 */

37 #if SQLITE_TEST	43 #if SQLITE_TEST

38 int sqlite3_btree_trace=0; /* True to enable tracing */	44 int sqlite3_btree_trace=0; /* True to enable tracing */

39 #endif	45 #endif

40	46

41 /*	47 /*

42 ** Forward declaration	48 ** Forward declaration

43 */	49 */

44 static int checkReadLocks(Btree,Pgno,BtCursor);	50 static int checkReadLocks(Btree,Pgno,BtCursor);

45	51

46	52

47 #ifdef SQLITE_OMIT_SHARED_CACHE	53 #ifdef SQLITE_OMIT_SHARED_CACHE

48 /*	54 /*

49 ** The functions queryTableLock(), lockTable() and unlockAllTables()	55 ** The functions queryTableLock(), lockTable() and unlockAllTables()

50 ** manipulate entries in the BtShared.pLock linked list used to store	56 ** manipulate entries in the BtShared.pLock linked list used to store

51 ** shared-cache table level locks. If the library is compiled with the	57 ** shared-cache table level locks. If the library is compiled with the

52 ** shared-cache feature disabled, then there is only ever one user	58 ** shared-cache feature disabled, then there is only ever one user

53 ** of each BtShared structure and so this locking is not necessary.	59 ** of each BtShared structure and so this locking is not necessary.

54 ** So define the lock related functions as no-ops.	60 ** So define the lock related functions as no-ops.

55 */	61 */

56 #define queryTableLock(a,b,c) SQLITE_OK	62 #define queryTableLock(a,b,c) SQLITE_OK

57 #define lockTable(a,b,c) SQLITE_OK	63 #define lockTable(a,b,c) SQLITE_OK

58 #define unlockAllTables(a)	64 #define unlockAllTables(a)

59 #else	65 #else

60	66

61 /*	67 /*

62 ** Query to see if btree handle p may obtain a lock of type eLock	68 ** Query to see if btree handle p may obtain a lock of type eLock

63 ** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return	69 ** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return

64 ** SQLITE_OK if the lock may be obtained (by calling lockTable()), or	70 ** SQLITE_OK if the lock may be obtained (by calling lockTable()), or

65 ** SQLITE_LOCKED if not.	71 ** SQLITE_LOCKED if not.

66 */	72 */

67 static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){	73 static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){

68 BtShared *pBt = p->pBt;	74 BtShared *pBt = p->pBt;

69 BtLock *pIter;	75 BtLock *pIter;

70	76

71 /* This is a no-op if the shared-cache is not enabled */	77 /* This is a no-op if the shared-cache is not enabled */

72 if( 0==sqlite3ThreadDataReadOnly()->useSharedData ){	78 if( 0==sqlite3ThreadDataReadOnly()->useSharedData ){

73 return SQLITE_OK;	79 return SQLITE_OK;

74 }	80 }

75	81

76 /* This (along with lockTable()) is where the ReadUncommitted flag is	82 /* This (along with lockTable()) is where the ReadUncommitted flag is

77 ** dealt with. If the caller is querying for a read-lock and the flag is	83 ** dealt with. If the caller is querying for a read-lock and the flag is

78 ** set, it is unconditionally granted - even if there are write-locks	84 ** set, it is unconditionally granted - even if there are write-locks

79 ** on the table. If a write-lock is requested, the ReadUncommitted flag	85 ** on the table. If a write-lock is requested, the ReadUncommitted flag

80 ** is not considered.	86 ** is not considered.

81 **	87 **

(...skipping 6293 matching lines...) Show 10 above Show 10 below
6375 ** to allow poisoning to be rolled back, and the database is anyhow	6381 ** to allow poisoning to be rolled back, and the database is anyhow

6376 ** going bye-bye RSN.	6382 ** going bye-bye RSN.

6377 */	6383 */

6378 /* TODO(shess): Figure out if this might release the lock and let	6384 /* TODO(shess): Figure out if this might release the lock and let

6379 ** someone else get in there, which might deny us the lock a couple	6385 ** someone else get in there, which might deny us the lock a couple

6380 ** lines down.	6386 ** lines down.

6381 */	6387 */

6382 if( sqlite3BtreeIsInTrans(p) ) sqlite3BtreeRollback(p);	6388 if( sqlite3BtreeIsInTrans(p) ) sqlite3BtreeRollback(p);

6383	6389

6384 /* Start an exclusive transaction. This will check the headers, so	6390 /* Start an exclusive transaction. This will check the headers, so

6385 ** if someone else poisoned the database we should get an error.	6391 ** if someone else poisoned the database we should get an error.

6386 */	6392 */

6387 rc = sqlite3BtreeBeginTrans(p, 2);	6393 rc = sqlite3BtreeBeginTrans(p, 2);

6388 /* TODO(shess): Handle SQLITE_BUSY? */	6394 /* TODO(shess): Handle SQLITE_BUSY? */

6389 if( rc!=SQLITE_OK ) return rc;	6395 if( rc!=SQLITE_OK ) return rc;

6390	6396

6391 /* Copied from sqlite3BtreeUpdateMeta(). Writing the old version of	6397 /* Copied from sqlite3BtreeUpdateMeta(). Writing the old version of

6392 ** the page to the journal may be overkill, but it probably won't	6398 ** the page to the journal may be overkill, but it probably won't

6393 ** hurt.	6399 ** hurt.

6394 */	6400 */

6395 assert( pBt->inTrans==TRANS_WRITE );	6401 assert( pBt->inTrans==TRANS_WRITE );

6396 assert( pBt->pPage1!=0 );	6402 assert( pBt->pPage1!=0 );

6397 rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);	6403 rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);

6398 if( rc ) goto err;	6404 if( rc ) goto err;

6399	6405

6400 /* "SQLite format 3" changes to	6406 /* "SQLite format 3" changes to

6401 ** "SQLite poison 3". Be extra paranoid about making this change.	6407 ** "SQLite poison 3". Be extra paranoid about making this change.

6402 */	6408 */

6403 if( sizeof(zMagicHeader)!=16 \|\|	6409 if( sizeof(zMagicHeader)!=16 \|\|

6404 sizeof(zPoisonHeader)!=sizeof(zMagicHeader) ){	6410 sizeof(zPoisonHeader)!=sizeof(zMagicHeader) ){

6405 rc = SQLITE_ERROR;	6411 rc = SQLITE_ERROR;

6406 goto err;	6412 goto err;

6407 }	6413 }

6408 pP1 = pBt->pPage1->aData;	6414 pP1 = pBt->pPage1->aData;

6409 if( memcmp(pP1, zMagicHeader, 16)!=0 ){	6415 if( memcmp(pP1, zMagicHeader, 16)!=0 ){

6410 rc = SQLITE_CORRUPT;	6416 rc = SQLITE_CORRUPT;

6411 goto err;	6417 goto err;

6412 }	6418 }

6413 memcpy(pP1, zPoisonHeader, 16);	6419 memcpy(pP1, zPoisonHeader, 16);

6414	6420

6415 /* Push it to the database file. */	6421 /* Push it to the database file. */

6416 return sqlite3BtreeCommit(p);	6422 return sqlite3BtreeCommit(p);

6417	6423

6418 err:	6424 err:

6419 /* TODO(shess): What about errors, here? */	6425 /* TODO(shess): What about errors, here? */

6420 sqlite3BtreeRollback(p);	6426 sqlite3BtreeRollback(p);

6421 return rc;	6427 return rc;

6422 }	6428 }

6423	6429

6424 #endif	6430 #endif

	6431

	6432 int sqlite3_get_user_version(sqlite3 sqlite, int user_version) {

	6433 Btree *bt;

	6434

	6435 if( sqlite == NULL ) return SQLITE_ERROR;

	6436 if( sqlite->nDb<1 ) return SQLITE_ERROR;

	6437

	6438 /* grab actual (not temporary tables) database */
	Scott.Hess 2008/05/22 23:44:28 Comments should mostly be composed of sentences. Comments should mostly be composed of sentences. Also next comment below. "Temporary" aside is probably confusing, just "Grab main database." should probably suffice. Dimitri 2008/06/04 03:02:16 On 2008/05/22 23:44:28, Scott.Hess wrote: > Commen On 2008/05/22 23:44:28, Scott.Hess wrote: > Comments should mostly be composed of sentences. Also next comment below. > "Temporary" aside is probably confusing, just "Grab main database." should > probably suffice. Done.
	6439 bt = sqlite->aDb[0].pBt;

	6440 /* because sqlite3BtreeGetMeta sets a table read lock, it is safe to use

	6441 ** without explicit read transaction. Besides, it is very unlikely we will

	6442 ** ever call this outside of a transaction.

	6443 */

	6444 return sqlite3BtreeGetMeta(bt, kUserCookie, (u32 *)user_version);

	6445 }

	6446

	6447 int sqlite3_set_user_version(sqlite3 *sqlite, int user_version) {

	6448 Btree *bt;

	6449 int rc;

	6450

	6451 if( sqlite == NULL ) return SQLITE_ERROR;

	6452 if( sqlite->nDb<1 ) return SQLITE_ERROR;

	6453

	6454 bt = sqlite->aDb[0].pBt;

	6455 if( bt->inTrans!= TRANS_WRITE ) {
	Scott.Hess 2008/05/22 23:44:28 Shouldn't this be ==? No space after = sign in an Shouldn't this be ==? No space after = sign in any case :-). Dimitri 2008/06/04 03:02:16 On 2008/05/22 23:44:28, Scott.Hess wrote: > Should On 2008/05/22 23:44:28, Scott.Hess wrote: > Shouldn't this be ==? No space after = sign in any case :-). Done. See discussion on this below.
	6456 return sqlite3BtreeUpdateMeta(bt, kUserCookie, (u32)user_version);

	6457 }else{

	6458 /* transacion isn't already in progress, have to enclose in

	6459 ** a write-transaction

	6460 */
	Scott.Hess 2008/05/22 23:44:28 sp on first occurrence of transaction. Revise com sp on first occurrence of transaction. Revise comment to create a sentence.
	6461 rc = sqlite3BtreeBeginTrans(bt, 1);

	6462 if( rc!=SQLITE_OK ) return rc;

	6463 rc = sqlite3BtreeUpdateMeta(bt, kUserCookie, (u32)user_version);

	6464 if( rc==SQLITE_OK ) return sqlite3BtreeCommit(bt);

	6465 sqlite3BtreeRollback(bt);

	6466 return rc;
	Scott.Hess 2008/05/22 23:44:28 For Database2, is it even possible to get to this For Database2, is it even possible to get to this point and not be in a transaction? Given how we're using this function, I'd almost be willing to throw SQLITE_MISUSE or something of the sort if a transaction is not open. I worry about messing with SQLite's transaction machinery. Dimitri 2008/06/04 03:02:16 On 2008/05/22 23:44:28, Scott.Hess wrote: > For Da On 2008/05/22 23:44:28, Scott.Hess wrote: > For Database2, is it even possible to get to this point and not be in a > transaction? Given how we're using this function, I'd almost be willing to > throw SQLITE_MISUSE or something of the sort if a transaction is not open. I > worry about messing with SQLite's transaction machinery. I think this is a very good idea. I am going with it. I modified the code to return SQLITE_MISUSE if called outside of a transaction.
	6467 }

	6468 }
	Scott.Hess 2008/05/22 23:44:28 Sorry to be a pain, I'm trying to recall why we're Sorry to be a pain, I'm trying to recall why we're doing this this way. Doing the transaction magic makes me worry that we're going to screw up transactions in some way. Did you try writing code up in database_utils.cc to lift off the authorizer while running PRAGMA user-version? The authorizer's userdata parameter should be able to accomplish this (allowing the authorizer to change results based on state). There's currently no context which can be associated with a particular sqlite3 handle, but OpenSqliteDatabase() is always called in creating a Database object, so such context could reasonably be added. [Note that this thinking is 90% around the transaction magic. If we removed that, then I'd be less worried about doing things this way.] Dimitri 2008/06/04 03:02:16 On 2008/05/22 23:44:28, Scott.Hess wrote: > Sorry On 2008/05/22 23:44:28, Scott.Hess wrote: > Sorry to be a pain, I'm trying to recall why we're doing this this way. Doing > the transaction magic makes me worry that we're going to screw up transactions > in some way. Did you try writing code up in database_utils.cc to lift off the > authorizer while running PRAGMA user-version? The authorizer's userdata > parameter should be able to accomplish this (allowing the authorizer to change > results based on state). There's currently no context which can be associated > with a particular sqlite3 handle, but OpenSqliteDatabase() is always called in > creating a Database object, so such context could reasonably be added. > > [Note that this thinking is 90% around the transaction magic. If we removed > that, then I'd be less worried about doing things this way.] If I recall correctly, I started with OP_SetCookie/OP_ReadCookie and traced back to see how a pragma operation would be executed using VDBE interpreter. I can not vouch for a 100% correct traceback, though, so I am perfectly happy with the solution you offered. As for unit tests, unless there are any objectsions, I am putting them into gears/database2/sqlite_user_version_test.cc\|h. This should place them next to the code that uses the features.
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