Documentation Source Text

Check-in [5279eb6057]
Login

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

Overview
Comment:Merge fixes from the release branch.
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256:5279eb6057bbf02855f88787d73a611b679d1db23909dcaf28a9402ab210ccb1
User & Date: drh 2018-02-01 14:44:35
Context
2018-02-05
00:32
The SCRIPT_FILENAME cgi parameter in althttpd is now a full pathname. check-in: f30335da5c user: drh tags: trunk
2018-02-04
21:41
Use Wapp to implement the search function. Search can now be run from the command-line using "./tclsh.docsrc doc/search". check-in: 33c56bee81 user: drh tags: search-refactor
2018-02-01
14:44
Merge fixes from the release branch. check-in: 5279eb6057 user: drh tags: trunk
14:43
Fix a typo in the flattening rules of the optoverview.html document. check-in: 20ecb45b42 user: drh tags: branch-3.22
2018-01-30
23:44
Remove an unused variable from althttpd.c. check-in: 94b9b95bee user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to pages/howtocorrupt.in.

471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
...
528
529
530
531
532
533
534
535
536
537
538
539
or thread might then try to modify the database using a stale cache and
cause database corruption.</p>

<p>This problem was discovered during internal testing and has never been
observed in the wild.  The problem was fixed on 2011-01-27 and in version
3.7.5.</p>

<h2> I/O while obtaining a lock leads to corruption</h2>

<p>If the operating system returns an I/O error while attempting to obtain
a certain lock on shared memory in [WAL | WAL mode] then SQLite might fail 
to reset its cache,
which could lead to database corruption if subsequent writes are attempted.</p>

<p>Note that this problem only occurs if the attempt to acquire the lock
................................................................................
of recovery because the previous process writing to it crashed in the
middle of a transaction and two or more processes try to open the 
that database at the same time, then the race condition might cause
one of those processes to get a false indication that the recovery 
has already completed, allowing that process to continue using the
database file without running recovery first.  If that process writes
to the file, then the file might go corrupt.  This race condition
had apparently existing in all prior versions of SQLite for Windows going
back to 2004.  But the race was very tight.  Practically speaking, you
need a fast multi-core machine in which you launch two processes to run
recovery at the same moment on two separate cores.  This defect was
on Windows systems only and did not affect the posix OS interface.</p>







|







 







|




471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
...
528
529
530
531
532
533
534
535
536
537
538
539
or thread might then try to modify the database using a stale cache and
cause database corruption.</p>

<p>This problem was discovered during internal testing and has never been
observed in the wild.  The problem was fixed on 2011-01-27 and in version
3.7.5.</p>

<h2> I/O error while obtaining a lock leads to corruption</h2>

<p>If the operating system returns an I/O error while attempting to obtain
a certain lock on shared memory in [WAL | WAL mode] then SQLite might fail 
to reset its cache,
which could lead to database corruption if subsequent writes are attempted.</p>

<p>Note that this problem only occurs if the attempt to acquire the lock
................................................................................
of recovery because the previous process writing to it crashed in the
middle of a transaction and two or more processes try to open the 
that database at the same time, then the race condition might cause
one of those processes to get a false indication that the recovery 
has already completed, allowing that process to continue using the
database file without running recovery first.  If that process writes
to the file, then the file might go corrupt.  This race condition
had apparently existed in all prior versions of SQLite for Windows going
back to 2004.  But the race was very tight.  Practically speaking, you
need a fast multi-core machine in which you launch two processes to run
recovery at the same moment on two separate cores.  This defect was
on Windows systems only and did not affect the posix OS interface.</p>

Changes to pages/optoverview.in.

1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
  <li value="1">  <i>(Obsolete.  Query flattening is no longer
                      attempted for aggregate subqueries.)</i>

  <li value="2">  <i>(Obsolete.  Query flattening is no longer
                      attempted for aggregate subqueries.)</i>

  <li value="3">
  ^If the subquery is not the right operand of a LEFT JOIN then
   <ol type="a"><li> the subquery may not be a join, and
   <li> the FROM clause of the subquery may
   not contain a virtual table, and
   <li> the outer query may not be an aggregate.</ol></li>

  <li value="4">  ^The subquery is not DISTINCT.








|







1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
  <li value="1">  <i>(Obsolete.  Query flattening is no longer
                      attempted for aggregate subqueries.)</i>

  <li value="2">  <i>(Obsolete.  Query flattening is no longer
                      attempted for aggregate subqueries.)</i>

  <li value="3">
  ^If the subquery is the right operand of a LEFT JOIN then
   <ol type="a"><li> the subquery may not be a join, and
   <li> the FROM clause of the subquery may
   not contain a virtual table, and
   <li> the outer query may not be an aggregate.</ol></li>

  <li value="4">  ^The subquery is not DISTINCT.