Documentation Source Text

proc chng {date desc {options {}}} {
  global nChng aChng xrefChng
  set aChng($nChng) [list $date $desc $options]
  set xrefChng($date) $nChng
  incr nChng
}

chng {2017-02-10 (3.17.0)} {
<li>Approximately 25% better performance from the [R-Tree extension].
    <ul>
    <li> Uses compiler built-ins (ex: __builtin_bswap32() or _byteswap_ulong())
         for byteswapping when available.
    <li> Uses the [sqlite3_blob] key/value access object instead of SQL
         for pulling content out of R-Tree nodes
    <li> Other miscellaneous enhancements such as loop unrolling.
    </ul>
<li>Add the [SQLITE_DEFAULT_LOOKASIDE] compile-time option.
<li>Increase the default [lookaside memory allocator|lookaside]
    size from 512,125 to 1200,100 
    as this provides better performance while only adding 56KB 
    of extra memory per connection.  Memory-sensitive 

#    ORDER BY mtime DESC;
#
# A small amount of manual editing and de-duplication followed.
#
# Manually edit the list for each subsequent release.
#      
foreach line [split {
ad867e8701|2017-02-10|version 3.17.0
a65a62893c|2017-01-06|version 3.16.2
979f043928|2017-01-03|Version 3.16.1
04ac0b75b1|2017-01-02|Version 3.16.0
bbd85d235f|2016-11-28|Version 3.15.2
1136863c76|2016-11-04|Version 3.15.1
707875582f|2016-10-14|Version 3.15.0
29dbef4b85|2016-09-12|Version 3.14.2
a12d805977|2016-08-11|Version 3.14.1
d5e9805702|2016-08-08|Version 3.14

is the size of each page-cache allocation.  N is the maximum 
number of available allocations.</p>

<p>If SQLite needs a page-cache entry that is larger than "sz" bytes or
if it needs more than N entries, it falls back to using the
general-purpose memory allocator.</p>

<tcl>hd_fragment lookaside {lookaside memory allocator} \
   {lookaside buffer} {lookaside memory} {lookaside}</tcl>
<h2> Lookaside memory allocator</h2>

<p>SQLite [database connections] make many
small and short-lived memory allocations.
This occurs most commonly when compiling SQL statements using
[sqlite3_prepare_v2()] but also to a lesser extent when running
[prepared statements] using [sqlite3_step()].  These small memory

running in a single thread (there are mutexes already in
place to enforce this) so no additional mutexing is required to 
serialize access to the lookaside slot freelist.
Consequently, lookaside memory
allocations and deallocations are very fast.  In speed tests on
Linux and Mac OS X workstations, SQLite has shown overall performance
improvements as high as 10% and 15%, depending on the workload how
and lookaside is configured.</p>

<p>The size of the lookaside memory pool has a global default value
but can also be configured on a connection-by-connection basis.
To change the default size of the lookaside memory pool at
compile-time, use the 
[SQLITE_DEFAULT_LOOKASIDE|-DSQLITE_DEFAULT_LOOKASIDE=<i>SZ,N</i>]
option.
To change the default size of the lookaside memory pool at
start-time, use the [sqlite3_config()] interface:</p>

<blockquote><pre>
[sqlite3_config]([SQLITE_CONFIG_LOOKASIDE], sz, cnt);
</pre></blockquote>

<p>The "sz" parameter is the size in bytes of each lookaside slot.
The "cnt" parameter is
the total number of lookaside memory slots per database connection.
The total amount
of lookaside memory allocated to each [database connection] is
sz*cnt bytes. 



</p>

<p>The lookaside pool can be changed for an individual
[database connection] "db" using this call:</p>

<blockquote><pre>
[sqlite3_db_config](db, [SQLITE_DBCONFIG_LOOKASIDE], pBuf, sz, cnt);

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

newsitem {2017-02-10} {Release 3.17.0} {
SQLite [version 3.17.0] is a regularly scheduled maintenance release.
<p>
Most of the changes in this release are performance optimizations.
Optimizations to the [R-Tree extension] are especially noticeable.
<p>
In this release, the default size of the 
[lookside buffer] allocated for each database connection
is increased from 64,000 to 120,000 bytes.  This provides improved
performance on many common workloads in exchange for a small increase
in memory usage.
Applications that value a small memory footprint over raw speed
can change the lookaside buffer size back to its old value (or to zero)
using the [SQLITE_DEFAULT_LOOKASIDE] compile-time option, or the
[SQLITE_CONFIG_LOOKASIDE|sqlite3_config(SQLITE_CONFIG_LOOKASIDE)]
start-time setting, or the
[SQLITE_DBCONFIG_LOOKASIDE|sqlite3_db_config(SQLITE_DBCONFIG_LOOKASIDE)]
run-time setting.
}

newsitem {2017-01-06} {Release 3.16.2} {
One of the performance optimizations added in 3.16.0 caused triggers
and foreign keys to malfunction for the [REPLACE] statement on
[WITHOUT ROWID] tables that lack secondary indexes.  This patch
release fixes the problem.  See ticket 
[https://www.sqlite.org/src/info/30027b613b4|30027b613b4] for details.