Documentation Source Text

^If L is greater than zero then integers with array indexes between 2 and
L+1 inclusive contain page numbers for freelist leaf pages.</p>

<p>Freelist leaf pages contain no information.  ^SQLite avoids reading or
writing freelist leaf pages in order to reduce disk I/O.</p>

<p>A bug in SQLite versions prior to 3.6.0 caused the database to be
reported as corrupt if any last 6 entries in the freelist trunk page 
array contained non-zero values.  Newer versions of SQLite do not have
this problem.  ^However, newer versions of SQLite still avoid using the 
last six entries in the freelist trunk page array in order that database
files created by newer versions of SQLite can be read by older versions
of SQLite.</p>

<p>^The number of freelist pages is stored as a 4-byte big-endian integer

^If L is greater than zero then integers with array indexes between 2 and
L+1 inclusive contain page numbers for freelist leaf pages.</p>

<p>Freelist leaf pages contain no information.  ^SQLite avoids reading or
writing freelist leaf pages in order to reduce disk I/O.</p>

<p>A bug in SQLite versions prior to 3.6.0 caused the database to be
reported as corrupt if any of the last 6 entries in the freelist trunk page 
array contained non-zero values.  Newer versions of SQLite do not have
this problem.  ^However, newer versions of SQLite still avoid using the 
last six entries in the freelist trunk page array in order that database
files created by newer versions of SQLite can be read by older versions
of SQLite.</p>

<p>^The number of freelist pages is stored as a 4-byte big-endian integer

<tcl>hd_fragment disopttest</tcl>
<h2>9.0 Disabled Optimization Tests</h2>

<p>The [sqlite3_test_control]([SQLITE_TESTCTRL_OPTIMIZATIONS], ...) interface
allows selected SQL statement optimizations to be disabled at run-time.
SQLite should always generate exactly the same answer with optimizations
enabled as with optimizations disable; the answer simply arrives quicker
with the optimizations turned on.  So in a production environment, one always
leaves the optimizations turned on (the default setting).</p>

<p>One verification technique used on SQLite is to run an entire test suite
twice, once with optimizations left on and a second time with optimizations
turned off, and verify that the same output is obtained both times.  This
verifies that the optimizations do not introduce errors.</p>
................................................................................
<p>Not all test cases can be handled this way.  Some test cases check
to verify that the optimizations really are reducing the amount of
computation by counting the number of disk accesses, sort operations, 
full-scan steps, or other processing steps that occur during queries.
Those test cases will appear to fail when optimizations are disabled.
But the majority of test cases simply look to see if the correct answer
was obtained, and all of those cases can be run successfully with and
without the optimizations, in order to show that the optimizations do
cause malfunctions.</p>

<tcl>hd_fragment staticanalysis</tcl>
<h2>10.0 Static Analysis</h2>

<p>Static analysis means analyzing code at or before compile-time to
check for correctness.  Static analysis consists mostly of making

<tcl>hd_fragment disopttest</tcl>
<h2>9.0 Disabled Optimization Tests</h2>

<p>The [sqlite3_test_control]([SQLITE_TESTCTRL_OPTIMIZATIONS], ...) interface
allows selected SQL statement optimizations to be disabled at run-time.
SQLite should always generate exactly the same answer with optimizations
enabled and with optimizations disabled; the answer simply arrives quicker
with the optimizations turned on.  So in a production environment, one always
leaves the optimizations turned on (the default setting).</p>

<p>One verification technique used on SQLite is to run an entire test suite
twice, once with optimizations left on and a second time with optimizations
turned off, and verify that the same output is obtained both times.  This
verifies that the optimizations do not introduce errors.</p>
................................................................................
<p>Not all test cases can be handled this way.  Some test cases check
to verify that the optimizations really are reducing the amount of
computation by counting the number of disk accesses, sort operations, 
full-scan steps, or other processing steps that occur during queries.
Those test cases will appear to fail when optimizations are disabled.
But the majority of test cases simply look to see if the correct answer
was obtained, and all of those cases can be run successfully with and
without the optimizations, in order to show that the optimizations do not
cause malfunctions.</p>

<tcl>hd_fragment staticanalysis</tcl>
<h2>10.0 Static Analysis</h2>

<p>Static analysis means analyzing code at or before compile-time to
check for correctness.  Static analysis consists mostly of making