SQLite

Check-in [05700c11a9]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Fix a comment in btree.c (CVS 3702)
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 05700c11a9e5177a437d2240e72fb61ea47b973b
User & Date: drh 2007-03-19 11:54:10.000
Context
2007-03-19
13:53
Fix some problems with test cases in shared_err.test. Also a real bug causing a segfault after an IO error in pager.c. (CVS 3703) (check-in: 9f62ef1ec3 user: danielk1977 tags: trunk)
11:54
Fix a comment in btree.c (CVS 3702) (check-in: 05700c11a9 user: drh tags: trunk)
11:25
Changes to support medium sector sizes larger than the database page size. (CVS 3701) (check-in: 3a3e8eb25d user: danielk1977 tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/btree.c. 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

/*
** 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 1.339 2007/03/19 11:25:20 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.












|








1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

/*
** 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 1.340 2007/03/19 11:54:10 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
︙︙
2645
2646
2647
2648
2649
2650
2651


2652


2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677

** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met.  These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1:  The cursor must have been opened with wrFlag==1
**


** 2:  No other cursors may be open with wrFlag==0 on the same table


**
** 3:  The database must be writable (not on read-only media)
**
** 4:  There must be an active transaction.
**
** Condition 2 warrants further discussion.  If any cursor is opened
** on a table with wrFlag==0, that prevents all other cursors from
** writing to that table.  This is a kind of "read-lock".  When a cursor
** is opened with wrFlag==0 it is guaranteed that the table will not
** change as long as the cursor is open.  This allows the cursor to
** do a sequential scan of the table without having to worry about
** entries being inserted or deleted during the scan.  Cursors should
** be opened with wrFlag==0 only if this read-lock property is needed.
** That is to say, cursors should be opened with wrFlag==0 only if they
** intend to use the sqlite3BtreeNext() system call.  All other cursors
** should be opened with wrFlag==1 even if they never really intend
** to write.
** 
** No checking is done to make sure that page iTable really is the
** root page of a b-tree.  If it is not, then the cursor acquired
** will not work correctly.
**
** The comparison function must be logically the same for every cursor
** on a particular table.  Changing the comparison function will result
** in incorrect operations.  If the comparison function is NULL, a








>
>
|
>
>





<
<
<
<
<
<
<
<
<
<
<
<
<








2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661













2662
2663
2664
2665
2666
2667
2668

** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met.  These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1:  The cursor must have been opened with wrFlag==1
**
** 2:  Other database connections that share the same pager cache
**     but which are not in the READ_UNCOMMITTED state may not have
**     cursors open with wrFlag==0 on the same table.  Otherwise
**     the changes made by this write cursor would be visible to
**     the read cursors in the other database connection.
**
** 3:  The database must be writable (not on read-only media)
**
** 4:  There must be an active transaction.
**













** No checking is done to make sure that page iTable really is the
** root page of a b-tree.  If it is not, then the cursor acquired
** will not work correctly.
**
** The comparison function must be logically the same for every cursor
** on a particular table.  Changing the comparison function will result
** in incorrect operations.  If the comparison function is NULL, a
︙︙