SQLite

/*
** 2004 April 6
**
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.383 2007/05/17 18:28:11 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"

  *pnSize = info.nSize;
  spaceLeft = info.nLocal;
  pPayload = &pCell[nHeader];
  pPrior = &pCell[info.iOverflow];

  while( nPayload>0 ){
    if( spaceLeft==0 ){
      int isExact = 0;
#ifndef SQLITE_OMIT_AUTOVACUUM
      Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
      if( pBt->autoVacuum ){
        do{
          pgnoOvfl++;
        } while( 
          PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt) 
        );
        if( pgnoOvfl>1 ){
          /* isExact = 1; */
        }
      }
#endif
      rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, isExact);
#ifndef SQLITE_OMIT_AUTOVACUUM
      /* If the database supports auto-vacuum, and the second or subsequent
      ** overflow page is being allocated, add an entry to the pointer-map
      ** for that page now. The entry for the first overflow page will be
      ** added later, by the insertCell() routine.
      */
      if( pBt->autoVacuum && pgnoPtrmap!=0 && rc==SQLITE_OK ){

#    May you share freely, never taking more than you give.
#
#*************************************************************************
# This file implements regression tests for SQLite library. The 
# focus of this script is testing that the overflow-page related
# enhancements added after version 3.3.17 speed things up.
#
# $Id: speed3.test,v 1.2 2007/05/17 18:28:11 danielk1977 Exp $
#

#---------------------------------------------------------------------
# Test plan:
#
# If auto-vacuum is enabled for the database, the following cases
# should show performance improvement with respect to 3.3.17.

  array set stats1 [btree_pager_stats [btree_from_db db]]
  array set stats2 [btree_pager_stats [btree_from_db db 2]]
# puts "1: [array get stats1]"
# puts "2: [array get stats2]"
  puts "Incrvacuum: Read $stats1(read), wrote $stats1(write)"
  puts "Normal    : Read $stats2(read), wrote $stats2(write)"
}

proc overflow_report {db} {
  set bt [btree_from_db db]
  set csr [btree_cursor $bt 3 0]

  for {btree_first $csr} {![btree_eof $csr]} {btree_next $csr} {
    puts "[btree_ovfl_info $bt $csr]"
  }

  btree_close_cursor $csr
  
}

proc reset_db {} {
  db close
  sqlite3 db test.db
  db eval { 
    PRAGMA main.cache_size = 200000;
    PRAGMA main.auto_vacuum = 'incremental';

    PRAGMA aux.auto_vacuum;
  }
} {2 0}

# Delete all content in a table, one row at a time.
#
#io_log db
#overflow_report db
reset_db
speed_trial speed3-1.incrvacuum $::NROW row {DELETE FROM main.t1 WHERE 1}
speed_trial speed3-1.normal     $::NROW row {DELETE FROM aux.t1 WHERE 1}
io_log db

# Select the "C" column (located at the far end of the overflow 
# chain) from each table row.
#
#db eval {PRAGMA incremental_vacuum(500000)}
populate_t1 db
#overflow_report db
reset_db
speed_trial speed3-2.incrvacuum $::NROW row {SELECT c FROM main.t1}
speed_trial speed3-2.normal     $::NROW row {SELECT c FROM aux.t1}
io_log db

finish_test