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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Use the MEMDB macro instead of OMIT_MEMORYDB in pager_recycle(). (CVS 3813)
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Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 97c5159816e211d9c71aa68db7c5e01df535d6a4
User & Date: danielk1977 2007-04-05 14:29:43
Context
2007-04-05
17:15
Always truncate the pager cache when truncating the database file. Also reorganize the code to check the change-counter after first obtaining a shared lock. (CVS 3814) check-in: 9dc4100e user: danielk1977 tags: trunk
14:29
Use the MEMDB macro instead of OMIT_MEMORYDB in pager_recycle(). (CVS 3813) check-in: 97c51598 user: danielk1977 tags: trunk
13:12
Avoid attempting to reclaim memory from in-memory databases in sqlite3_release_memory(). (CVS 3812) check-in: c20f7563 user: danielk1977 tags: trunk
Changes
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Changes to src/pager.c.

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** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.321 2007/04/05 13:12:14 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
** been released, the function returns. A negative value for nReq means
** free as much memory as possible. The return value is the total number 
** of bytes of memory released.
*/
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
int sqlite3PagerReleaseMemory(int nReq){
  const ThreadData *pTsdro = sqlite3ThreadDataReadOnly();
  Pager *p;
  int nReleased = 0;
  int i;

  /* If the the global mutex is held, this subroutine becomes a
  ** o-op; zero bytes of memory are freed.  This is because
  ** some of the code invoked by this function may also
  ** try to obtain the mutex, resulting in a deadlock.
................................................................................
  ** iteration (which only runs if the first failed to free nReq bytes of
  ** memory) is permitted to call fsync(). This is of course much more 
  ** expensive.
  */
  for(i=0; i<=1; i++){

    /* Loop through all the SQLite pagers opened by the current thread. */

    for(p=pTsdro->pPager; p && (nReq<0 || nReleased<nReq); p=p->pNext){
      PgHdr *pPg;
      int rc;

#ifndef SQLITE_OMIT_MEMORYDB
      if( p->memDb ){
        continue;
      }
#endif

      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(p, i, &pPg)) && pPg) {
        /* We've found a page to free. At this point the page has been 
        ** removed from the page hash-table, free-list and synced-list 
        ** (pFirstSynced). It is still in the all pages (pAll) list. 
        ** Remove it from this list before freeing.
        **
        ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
        ** probably is though.
        */
        PgHdr *pTmp;
        assert( pPg );
        page_remove_from_stmt_list(pPg);
        if( pPg==p->pAll ){
           p->pAll = pPg->pNextAll;
        }else{
          for( pTmp=p->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll ){}
          pTmp->pNextAll = pPg->pNextAll;
        }
        nReleased += sqliteAllocSize(pPg);
        sqliteFree(pPg);
      }

      if( rc!=SQLITE_OK ){
................................................................................
        /* An error occured whilst writing to the database file or 
        ** journal in pager_recycle(). The error is not returned to the 
        ** caller of this function. Instead, set the Pager.errCode variable.
        ** The error will be returned to the user (or users, in the case 
        ** of a shared pager cache) of the pager for which the error occured.
        */
        assert( (rc&0xff)==SQLITE_IOERR || rc==SQLITE_FULL );
        assert( p->state>=PAGER_RESERVED );
        pager_error(p, rc);
      }
    }
  }

  return nReleased;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */







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** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.322 2007/04/05 14:29:43 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
** been released, the function returns. A negative value for nReq means
** free as much memory as possible. The return value is the total number 
** of bytes of memory released.
*/
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
int sqlite3PagerReleaseMemory(int nReq){
  const ThreadData *pTsdro = sqlite3ThreadDataReadOnly();

  int nReleased = 0;
  int i;

  /* If the the global mutex is held, this subroutine becomes a
  ** o-op; zero bytes of memory are freed.  This is because
  ** some of the code invoked by this function may also
  ** try to obtain the mutex, resulting in a deadlock.
................................................................................
  ** iteration (which only runs if the first failed to free nReq bytes of
  ** memory) is permitted to call fsync(). This is of course much more 
  ** expensive.
  */
  for(i=0; i<=1; i++){

    /* Loop through all the SQLite pagers opened by the current thread. */
    Pager *pPager = pTsdro->pPager;
    for( ; pPager && (nReq<0 || nReleased<nReq); pPager=pPager->pNext){
      PgHdr *pPg;
      int rc;

      if( MEMDB ){

        continue;
      }


      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(pPager, i, &pPg)) && pPg) {
        /* We've found a page to free. At this point the page has been 
        ** removed from the page hash-table, free-list and synced-list 
        ** (pFirstSynced). It is still in the all pages (pAll) list. 
        ** Remove it from this list before freeing.
        **
        ** Todo: Check the Pager.pStmt list to make sure this is Ok. It 
        ** probably is though.
        */
        PgHdr *pTmp;
        assert( pPg );
        page_remove_from_stmt_list(pPg);
        if( pPg==pPager->pAll ){
           pPager->pAll = pPg->pNextAll;
        }else{
          for( pTmp=pPager->pAll; pTmp->pNextAll!=pPg; pTmp=pTmp->pNextAll ){}
          pTmp->pNextAll = pPg->pNextAll;
        }
        nReleased += sqliteAllocSize(pPg);
        sqliteFree(pPg);
      }

      if( rc!=SQLITE_OK ){
................................................................................
        /* An error occured whilst writing to the database file or 
        ** journal in pager_recycle(). The error is not returned to the 
        ** caller of this function. Instead, set the Pager.errCode variable.
        ** The error will be returned to the user (or users, in the case 
        ** of a shared pager cache) of the pager for which the error occured.
        */
        assert( (rc&0xff)==SQLITE_IOERR || rc==SQLITE_FULL );
        assert( pPager->state>=PAGER_RESERVED );
        pager_error(pPager, rc);
      }
    }
  }

  return nReleased;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */