Documentation Source Text

      <a href="http://www.sqlite.org/src/timeline">
      http://www.sqlite.org/src/timeline</a>.</p>
    }
    hd_close_aux
    hd_enable_main 1
  }
}











chng {2011 April 12 (3.7.6)} {
<li> Added the [sqlite3_wal_checkpoint_v2()] interface and enhanced the
     [wal_checkpoint pragma] to support blocking checkpoints.
<li> Improvements to the query planner so that it makes better estimates of
     plan costs and hence does a better job of choosing the right plan,
     especially when [SQLITE_ENABLE_STAT2] is used.

      <a href="http://www.sqlite.org/src/timeline">
      http://www.sqlite.org/src/timeline</a>.</p>
    }
    hd_close_aux
    hd_enable_main 1
  }
}

chng {2011 April 14 (3.7.6.1)} {
<li> Fix a bug in 3.7.6 that only appears if the [SQLITE_FCNTL_SIZE_HINT]
     file control is used with a build of SQLite that makes use of the
     HAVE_POSIX_FALLOCATE compile-time option and which has
     SQLITE_ENABLE_LOCKING_MODE turned off.
<li> SQLITE_SOURCE_ID:
     "2011-04-13 14:40:25 a35e83eac7b185f4d363d7fa51677f2fdfa27695"
<li> SHA1 for sqlite3.c: b81bfa27d3e09caf3251475863b1ce6dd9f6ab66
}

chng {2011 April 12 (3.7.6)} {
<li> Added the [sqlite3_wal_checkpoint_v2()] interface and enhanced the
     [wal_checkpoint pragma] to support blocking checkpoints.
<li> Improvements to the query planner so that it makes better estimates of
     plan costs and hence does a better job of choosing the right plan,
     especially when [SQLITE_ENABLE_STAT2] is used.

  <tr><th>Option<th>Interpretation
  <tr><td>matchinfo<td> This option may only be set to the value "fts3".
    Attempting to set it otherwise is an error. If this option is specified,
    then some of the extra information stored by FTS4 is omitted. This reduces
    the amount of disk space consumed by an FTS4 table until it is almost the
    same as the amount that would be used by the equivalent FTS3 table, but 
    also means that the data accessed by passing the 'l' flag to the 
    [matchinfo()] function is not available. For example:

  <tr><td>compress<td>
    This option is used to specify the compress function. It is an error to
    specify a compress function without also specifying an uncompress
    function.
    
  <tr><td>uncompress<td>
................................................................................
<table striped=1>
  <tr><th>Column Name<th>Column Contents
  <tr><td>term<td> 
    Contains the text of the term for this row.
  <tr><td>col<td> 
    This column may contain either the text value '*' (i.e. a single 
    character, UTF codepoint 42) or an integer between 0 and N-1, where N is
    again the number of user-defined columns in the corresponing FTS table.

  <tr><td>documents<td>
    This column always contains an integer value greater than zero.
    <br><br>
    If the "col" column contains the value '*', then this column
    contains the number of rows of the FTS table that contain at least one
    instance of the term (in any column). If col contains an integer

  <tr><th>Option<th>Interpretation
  <tr><td>matchinfo<td> This option may only be set to the value "fts3".
    Attempting to set it otherwise is an error. If this option is specified,
    then some of the extra information stored by FTS4 is omitted. This reduces
    the amount of disk space consumed by an FTS4 table until it is almost the
    same as the amount that would be used by the equivalent FTS3 table, but 
    also means that the data accessed by passing the 'l' flag to the 
    [matchinfo()] function is not available.

  <tr><td>compress<td>
    This option is used to specify the compress function. It is an error to
    specify a compress function without also specifying an uncompress
    function.
    
  <tr><td>uncompress<td>
................................................................................
<table striped=1>
  <tr><th>Column Name<th>Column Contents
  <tr><td>term<td> 
    Contains the text of the term for this row.
  <tr><td>col<td> 
    This column may contain either the text value '*' (i.e. a single 
    character, UTF codepoint 42) or an integer between 0 and N-1, where N is
    again the number of user-defined columns in the corresponding FTS table.

  <tr><td>documents<td>
    This column always contains an integer value greater than zero.
    <br><br>
    If the "col" column contains the value '*', then this column
    contains the number of rows of the FTS table that contain at least one
    instance of the term (in any column). If col contains an integer

will occasionally ask the operating system to flush all pending writes to
persistent storage then wait for that flush to complete.  This is 
accomplished using the <tt>fsync()</tt> system call under unix and
<tt>FlushFileBuffers()</tt> under windows.  We call this flush of
pending writes a "sync".</p>

<p>Actually, if one is only concerned with atomic and consistent writes and
is willing to forego durable writes, the sync operation does not really need
to wait until the content is completely stored on persistent media.  Instead,
the sync operation can be thought of as an I/O barrier.  As long as all
writes that occur before the sync are completed before any write that happens
after the sync, no database corruption will occur.  If sync is operating as
an I/O barrier and not as a true sync, then a power failure or system crash
might cause one or more previously committed transactions to roll back
(in violation of the "durable" property of "ACID") but the database will at
................................................................................
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
resulted in an I/O error.  If the lock is simply not granted (because some
other thread or process is already holding a conflicting lock) then no
corruption will ever occur.  We are not aware of any operating systems that
will fail with an I/O error while attempting to get a file lock on shared
memory.  So this is really a theoretical problem rather than a real problem.
Needless to say, this problem has never been observed in the wild.  The
problem was discovered while doing stress testing of SQLite in a test
harness that simulates I/O errors.</p>

<p>This problem was fixed on 2010-09-20 for SQLite version 3.7.3.</p>

<h3>7.4 Database pages leak from the free page list</h3>

will occasionally ask the operating system to flush all pending writes to
persistent storage then wait for that flush to complete.  This is 
accomplished using the <tt>fsync()</tt> system call under unix and
<tt>FlushFileBuffers()</tt> under windows.  We call this flush of
pending writes a "sync".</p>

<p>Actually, if one is only concerned with atomic and consistent writes and
is willing to forego durable writes, the sync operation does not need
to wait until the content is completely stored on persistent media.  Instead,
the sync operation can be thought of as an I/O barrier.  As long as all
writes that occur before the sync are completed before any write that happens
after the sync, no database corruption will occur.  If sync is operating as
an I/O barrier and not as a true sync, then a power failure or system crash
might cause one or more previously committed transactions to roll back
(in violation of the "durable" property of "ACID") but the database will at
................................................................................
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
resulted in an I/O error.  If the lock is simply not granted (because some
other thread or process is already holding a conflicting lock) then no
corruption will ever occur.  We are not aware of any operating systems that
will fail with an I/O error while attempting to get a file lock on shared
memory.  So this is a theoretical problem rather than a real problem.
Needless to say, this problem has never been observed in the wild.  The
problem was discovered while doing stress testing of SQLite in a test
harness that simulates I/O errors.</p>

<p>This problem was fixed on 2010-09-20 for SQLite version 3.7.3.</p>

<h3>7.4 Database pages leak from the free page list</h3>

</td>
<td width="20"></td><td bgcolor="#044a64" width="1"></td><td width="20"></td>
<td valign="top">
<h3>Current Status</h3>

<p><ul>
<li><a href="releaselog/3_7_6.html">Version 3.7.6</a>
of SQLite is recommended for all new development.
Upgrading from version 3.7.5 is optional.
Upgrading from all SQLite versions prior to 3.7.5 is recommended.</li>
</ul></p>

<h3>Common Links</h3>

<p><ul>
<li> <a href="features.html">Features</a> </li>

</td>
<td width="20"></td><td bgcolor="#044a64" width="1"></td><td width="20"></td>
<td valign="top">
<h3>Current Status</h3>

<p><ul>
<li><a href="releaselog/3_7_6_1.html">Version 3.7.6.1</a>
of SQLite is recommended for all new development.
Upgrading from version 3.7.5 or 3.7.6 is optional.
Upgrading from all SQLite versions prior to 3.7.5 is recommended.</li>
</ul></p>

<h3>Common Links</h3>

<p><ul>
<li> <a href="features.html">Features</a> </li>

  hd_puts "<h3>$date - $title</h3>"
  regsub -all "\n( *\n)+" $text "</p>\n\n<p>" txt
  regsub -all {[Tt]icket #(\d+)} $txt \
      {<a href="http://www.sqlite.org/cvstrac/tktview?tn=\1">\0</a>} txt
  hd_resolve "<p>$txt</p>"
  hd_puts "<hr width=\"50%\">"
}












newsitem {2011-April-12} {Version 3.7.6} {
  SQLite [version 3.7.6] is a regularly scheduled bi-monthly maintenance
  release of SQLite.  Upgrading from version 3.7.5 is optional.  Upgrading
  releases prior to 3.7.5 is recommended.
}

  hd_puts "<h3>$date - $title</h3>"
  regsub -all "\n( *\n)+" $text "</p>\n\n<p>" txt
  regsub -all {[Tt]icket #(\d+)} $txt \
      {<a href="http://www.sqlite.org/cvstrac/tktview?tn=\1">\0</a>} txt
  hd_resolve "<p>$txt</p>"
  hd_puts "<hr width=\"50%\">"
}

newsitem {2011-April-13} {Version 3.7.6.1} {
  SQLite [version 3.7.6.1] fixes a single bug in 3.7.6 that can cause a
  segfault if [SQLITE_FCNTL_SIZE_HINT] is used on a unix build that has
  SQLITE_ENABLE_LOCKING_MODE set to 0 and is compiled with
  HAVE_POSIX_FALLOCATE.

  Upgrading from 3.7.6 is only needed for users effected by the 
  configuration-specific bug described above.  There are no other changes
  to the code.
}

newsitem {2011-April-12} {Version 3.7.6} {
  SQLite [version 3.7.6] is a regularly scheduled bi-monthly maintenance
  release of SQLite.  Upgrading from version 3.7.5 is optional.  Upgrading
  releases prior to 3.7.5 is recommended.
}