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Overview
Comment:When moving a page to make way for the root page of a new table or index in an auto-vacuum database, save the positions of any cursors that may be holding xFetch references to the page being moved.
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SHA1:9d9b1da54a555e8fb6037d63d1952458c12956d2
User & Date: dan 2013-04-03 11:38:36
Context
2013-04-03
11:52
Remove the restriction on using xFetch to load the root pages of tables and indexes. It appears to have been based on a misconception. check-in: 5b082efe user: dan tags: experimental-mmap
11:38
When moving a page to make way for the root page of a new table or index in an auto-vacuum database, save the positions of any cursors that may be holding xFetch references to the page being moved. check-in: 9d9b1da5 user: dan tags: experimental-mmap
11:17
In btree.c, save the positions of other cursors open on the same table when writing via an incremental blob handle. Otherwise, they may be left holding an out-of-date xFetch page reference. check-in: 3f09fba1 user: dan tags: experimental-mmap
Changes
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Changes to src/btree.c.

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      ** the new table (assuming an error did not occur). But we were
      ** allocated pgnoMove. If required (i.e. if it was not allocated
      ** by extending the file), the current page at position pgnoMove
      ** is already journaled.
      */
      u8 eType = 0;
      Pgno iPtrPage = 0;









      releasePage(pPageMove);

      /* Move the page currently at pgnoRoot to pgnoMove. */
      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0, 0);
      if( rc!=SQLITE_OK ){
        return rc;







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      ** the new table (assuming an error did not occur). But we were
      ** allocated pgnoMove. If required (i.e. if it was not allocated
      ** by extending the file), the current page at position pgnoMove
      ** is already journaled.
      */
      u8 eType = 0;
      Pgno iPtrPage = 0;

      /* Save the positions of any open cursors. This is required in
      ** case they are holding a reference to an xFetch reference
      ** corresponding to page pgnoRoot.  */
      rc = saveAllCursors(pBt, 0, 0);
      if( rc!=SQLITE_OK ){
        return rc;
      }

      releasePage(pPageMove);

      /* Move the page currently at pgnoRoot to pgnoMove. */
      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0, 0);
      if( rc!=SQLITE_OK ){
        return rc;

Changes to test/mmap1.test.

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do_test 4.4 {
  sqlite3_finalize $::STMT
} SQLITE_OK

do_execsql_test 4.5 { COMMIT }




















finish_test






























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do_test 4.4 {
  sqlite3_finalize $::STMT
} SQLITE_OK

do_execsql_test 4.5 { COMMIT }

#-------------------------------------------------------------------------
# Ensure that existing cursors holding xFetch() references are not 
# confused if those pages are moved to make way for the root page of a
# new table or index.
#
reset_db
do_execsql_test 5.1 {
  PRAGMA auto_vacuum = 2;
  PRAGMA page_size = 1024;
  CREATE TABLE t1(x);
  INSERT INTO t1 VALUES($aaa);
  INSERT INTO t1 VALUES($bbb);
  INSERT INTO t1 VALUES($ccc);
  INSERT INTO t1 VALUES($ddd);

  PRAGMA auto_vacuum;
  SELECT * FROM t1;
} [list 2 $aaa $bbb $ccc $ddd]

do_test 5.2 {
  set ::STMT [sqlite3_prepare db "SELECT * FROM t1 ORDER BY rowid" -1 dummy]
  sqlite3_step $::STMT
  sqlite3_column_text $::STMT 0
} $aaa

do_execsql_test 5.3 {
  CREATE TABLE t2(x);
  INSERT INTO t2 VALUES('tricked you!');
  INSERT INTO t2 VALUES('tricked you!');
}

do_test 5.4 {
  sqlite3_step $::STMT
  sqlite3_column_text $::STMT 0
} $bbb

do_test 5.5 {
  sqlite3_finalize $::STMT
} SQLITE_OK

finish_test