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Overview
Comment:Update comments and remove unused code in btree.c. No functional changes. (CVS 6521)
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SHA1:bd860184909b7a9cc32c59770ebcee0efdc491f0
User & Date: drh 2009-04-19 20:51:07
Context
2009-04-20
11:34
Speed improvements by avoiding unnecessary calls to fstat() and ftruncate(). (CVS 6522) check-in: 5b7e3a41 user: drh tags: trunk
2009-04-19
20:51
Update comments and remove unused code in btree.c. No functional changes. (CVS 6521) check-in: bd860184 user: drh tags: trunk
12:23
Make extra calls to sqlite3_shutdown() be harmless no-ops. (CVS 6520) check-in: d8082295 user: drh tags: trunk
Changes
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Changes to src/btree.c.

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** 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.
**
*************************************************************************
** $Id: btree.c,v 1.595 2009/04/11 16:06:15 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
      assert( pBt->pPage1->aData );
#if 0
      if( pBt->pPage1->aData==0 ){
        MemPage *pPage = pBt->pPage1;
        pPage->aData = sqlite3PagerGetData(pPage->pDbPage);
        pPage->pBt = pBt;
        pPage->pgno = 1;
      }
#endif
      releasePage(pBt->pPage1);
    }
    pBt->pPage1 = 0;
  }
}

/*
................................................................................
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal.  Then the contents of the journal are flushed out to
** the disk.  After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed.  See sqlite3BtreeCommit() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file 
................................................................................
  return rc;
}

/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit.  The
** sqlite3BtreeSync() routine does the first phase and should be invoked
** prior to calling this routine.  The sqlite3BtreeSync() routine did
** all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter.  All this
** routine has to do is delete or truncate the rollback journal
** (which causes the transaction to commit) and drop locks.

**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p){
  BtShared *pBt = p->pBt;

................................................................................
    clearAllSharedCacheTableLocks(p);
    pBt->nTransaction--;
    if( 0==pBt->nTransaction ){
      pBt->inTransaction = TRANS_NONE;
    }
  }

  /* Set the handles current transaction state to TRANS_NONE and unlock
  ** the pager if this call closed the only read or write transaction.
  */
  btreeClearHasContent(pBt);
  p->inTrans = TRANS_NONE;
  unlockBtreeIfUnused(pBt);

  btreeIntegrity(p);







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** 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.
**
*************************************************************************
** $Id: btree.c,v 1.596 2009/04/19 20:51:07 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

................................................................................
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
  assert( sqlite3_mutex_held(pBt->mutex) );
  if( pBt->inTransaction==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
    if( sqlite3PagerRefcount(pBt->pPager)>=1 ){
      assert( pBt->pPage1->aData );








      releasePage(pBt->pPage1);
    }
    pBt->pPage1 = 0;
  }
}

/*
................................................................................
** and populated with enough information so that if a power loss occurs
** the database can be restored to its original state by playing back
** the journal.  Then the contents of the journal are flushed out to
** the disk.  After the journal is safely on oxide, the changes to the
** database are written into the database file and flushed to oxide.
** At the end of this call, the rollback journal still exists on the
** disk and we are still holding all locks, so the transaction has not
** committed.  See sqlite3BtreeCommitPhaseTwo() for the second phase of the
** commit process.
**
** This call is a no-op if no write-transaction is currently active on pBt.
**
** Otherwise, sync the database file for the btree pBt. zMaster points to
** the name of a master journal file that should be written into the
** individual journal file, or is NULL, indicating no master journal file 
................................................................................
  return rc;
}

/*
** Commit the transaction currently in progress.
**
** This routine implements the second phase of a 2-phase commit.  The
** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
** be invoked prior to calling this routine.  The sqlite3BtreeCommitPhaseOne()
** routine did all the work of writing information out to disk and flushing the
** contents so that they are written onto the disk platter.  All this
** routine has to do is delete or truncate or zero the header in the
** the rollback journal (which causes the transaction to commit) and
** drop locks.
**
** This will release the write lock on the database file.  If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommitPhaseTwo(Btree *p){
  BtShared *pBt = p->pBt;

................................................................................
    clearAllSharedCacheTableLocks(p);
    pBt->nTransaction--;
    if( 0==pBt->nTransaction ){
      pBt->inTransaction = TRANS_NONE;
    }
  }

  /* Set the current transaction state to TRANS_NONE and unlock
  ** the pager if this call closed the only read or write transaction.
  */
  btreeClearHasContent(pBt);
  p->inTrans = TRANS_NONE;
  unlockBtreeIfUnused(pBt);

  btreeIntegrity(p);