Function ExecHashEstimate

src/backend/executor/nodeHash.c:3286–3299

* Reserve space in the DSM segment for instrumentation data. */

 * Reserve space in the DSM segment for instrumentation data.
 */
void
ExecHashEstimate(HashState *node, ParallelContext *pcxt)
{
	size_t		size;

	/* don't need this if not instrumenting or no workers */
	if (!node->ps.instrument || pcxt->nworkers == 0)
		return;

	size = mul_size(pcxt->nworkers, sizeof(HashInstrumentation));
	size = add_size(size, offsetof(SharedHashInfo, hinstrument));
	shm_toc_estimate_chunk(&pcxt->estimator, size);
	shm_toc_estimate_keys(&pcxt->estimator, 1);
}

/*
 * Set up a space in the DSM for all workers to record instrumentation data