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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Impose A Limit On Heap Size</h2><blockquote><pre>sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 N);
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</pre></blockquote><p>
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The sqlite3_soft_heap_limit64() interface sets and/or queries the
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soft limit on the amount of heap memory that may be allocated by SQLite.
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SQLite strives to keep heap memory utilization below the soft heap
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limit by reducing the number of pages held in the page cache
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as heap memory usages approaches the limit.
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The soft heap limit is "soft" because even though SQLite strives to stay
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below the limit, it will exceed the limit rather than generate
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an <a href="../c3ref/c_abort.html">SQLITE_NOMEM</a> error. In other words, the soft heap limit
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is advisory only.</p>
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<p>The return value from sqlite3_soft_heap_limit64() is the size of
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the soft heap limit prior to the call, or negative in the case of an
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error. If the argument N is negative
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then no change is made to the soft heap limit. Hence, the current
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size of the soft heap limit can be determined by invoking
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sqlite3_soft_heap_limit64() with a negative argument.</p>
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<p>If the argument N is zero then the soft heap limit is disabled.</p>
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<p>The soft heap limit is not enforced in the current implementation
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if one or more of following conditions are true:</p>
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<li> The soft heap limit is set to zero.
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<li> Memory accounting is disabled using a combination of the
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<a href="../c3ref/config.html">sqlite3_config</a>(<a href="../c3ref/c_config_getmalloc.html#sqliteconfigmemstatus">SQLITE_CONFIG_MEMSTATUS</a>,...) start-time option and
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the <a href="../compile.html#default_memstatus">SQLITE_DEFAULT_MEMSTATUS</a> compile-time option.
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<li> An alternative page cache implementation is specified using
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<a href="../c3ref/config.html">sqlite3_config</a>(<a href="../c3ref/c_config_getmalloc.html#sqliteconfigpcache2">SQLITE_CONFIG_PCACHE2</a>,...).
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<li> The page cache allocates from its own memory pool supplied
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by <a href="../c3ref/config.html">sqlite3_config</a>(<a href="../c3ref/c_config_getmalloc.html#sqliteconfigpagecache">SQLITE_CONFIG_PAGECACHE</a>,...) rather than
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<p>Beginning with SQLite version 3.7.3, the soft heap limit is enforced
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regardless of whether or not the <a href="../compile.html#enable_memory_management">SQLITE_ENABLE_MEMORY_MANAGEMENT</a>
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compile-time option is invoked. With <a href="../compile.html#enable_memory_management">SQLITE_ENABLE_MEMORY_MANAGEMENT</a>,
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the soft heap limit is enforced on every memory allocation. Without
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<a href="../compile.html#enable_memory_management">SQLITE_ENABLE_MEMORY_MANAGEMENT</a>, the soft heap limit is only enforced
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when memory is allocated by the page cache. Testing suggests that because
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the page cache is the predominate memory user in SQLite, most
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applications will achieve adequate soft heap limit enforcement without
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the use of <a href="../compile.html#enable_memory_management">SQLITE_ENABLE_MEMORY_MANAGEMENT</a>.</p>
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<p>The circumstances under which SQLite will enforce the soft heap limit may
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changes in future releases of SQLite.
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</p><p>See also lists of
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<a href="objlist.html">Objects</a>,
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<a href="constlist.html">Constants</a>, and
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<a href="funclist.html">Functions</a>.</p>
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