Using SQLite

Name

sqlite3_aggregate_context() — Allocate or retrieve aggregate state memory

Definition

void* sqlite3_aggregate_context( sqlite3_context* ctx, int size );

ctx

An SQL function context, provided by the SQLite library.

size

The memory allocation size, in bytes.

Returns

A pointer to the aggregate memory allocation.

Description

This function is used by an aggregate function implementation to allocate and retrieve a memory block. The first time it is called, a memory block of the requested size is allocated, all the bytes are set to zero, and the pointer is returned. Subsequent calls for the same function context will return the same block of memory. SQLite will automatically deallocate the memory after the aggregate finalize function is called.

This function is typically used to allocate and retrieve memory used to hold all the state information required to calculate an aggregate result. If the data structure needs to be initialized, a flag value is typically used. When the memory is first allocated, the flag will be set to zero (like the rest of the structure). On the first call, the structure can be initialized and the flag set to a nonzero value. Both the aggregate step and the finalize functions need to be prepared to initialize the memory.

See Also

sqlite3_create_function()