Impose A Limit On Heap Size

void sqlite3_soft_heap_limit(int);

The sqlite3_soft_heap_limit() interface places a "soft" limit on the amount of heap memory that may be allocated by SQLite. If an internal allocation is requested that would exceed the soft heap limit, sqlite3_release_memory() is invoked one or more times to free up some space before the allocation is made.

The limit is called "soft", because if sqlite3_release_memory() cannot free sufficient memory to prevent the limit from being exceeded, the memory is allocated anyway and the current operation proceeds.

A negative or zero value for N means that there is no soft heap limit and sqlite3_release_memory() will only be called when memory is exhausted. The default value for the soft heap limit is zero.

SQLite makes a best effort to honor the soft heap limit. But if the soft heap limit cannot honored, execution will continue without error or notification. This is why the limit is called a "soft" limit. It is advisory only.

Prior to SQLite version 3.5.0, this routine only constrained the memory allocated by a single thread - the same thread in which this routine runs. Beginning with SQLite version 3.5.0, the soft heap limit is applied to all threads. The value specified for the soft heap limit is an upper bound on the total memory allocation for all threads. In version 3.5.0 there is no mechanism for limiting the heap usage for individual threads.

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