Function AddInvalidationMessage

src/backend/utils/cache/inval.c:253–297

* AddInvalidationMessage * Add an invalidation message to a list (of chunks). * * Note that we do not pay any great attention to maintaining the original * ordering of the messages. */

 * ordering of the messages.
 */
static void
AddInvalidationMessage(InvalidationChunk **listHdr,
					   SharedInvalidationMessage *msg)
{
	InvalidationChunk *chunk = *listHdr;

	if (chunk == NULL)
	{
		/* First time through; create initial chunk */
#define FIRSTCHUNKSIZE 32
		chunk = (InvalidationChunk *)
			MemoryContextAlloc(CurTransactionContext,
							   offsetof(InvalidationChunk, msgs) +
							   FIRSTCHUNKSIZE * sizeof(SharedInvalidationMessage));
		chunk->nitems = 0;
		chunk->maxitems = FIRSTCHUNKSIZE;
		chunk->next = *listHdr;
		*listHdr = chunk;
	}
	else if (chunk->nitems >= chunk->maxitems)
	{
		/* Need another chunk; double size of last chunk */
		int			chunksize = 2 * chunk->maxitems;

		/*
		 * Keep in mind: the max allowed alloc size is about 1GB, for
		 * simplification we set the upper limit to half of that.
		 */
#define MAXCHUNKSIZE (MaxAllocSize / 2 / sizeof(SharedInvalidationMessage))
		if (chunksize > MAXCHUNKSIZE)
			chunksize >>= 1;

		chunk = (InvalidationChunk *)
			MemoryContextAlloc(CurTransactionContext,
							   offsetof(InvalidationChunk, msgs) +
							   chunksize * sizeof(SharedInvalidationMessage));
		chunk->nitems = 0;
		chunk->maxitems = chunksize;
		chunk->next = *listHdr;
		*listHdr = chunk;
	}
	/* Okay, add message to current chunk */
	chunk->msgs[chunk->nitems] = *msg;
	chunk->nitems++;
}

/*
 * Append one list of invalidation message chunks to another, resetting