Function CreateExprContextInternal

src/backend/executor/execUtils.c:287–342

* Internal implementation for CreateExprContext() and CreateWorkExprContext() * that allows control over the AllocSet parameters. */

 * that allows control over the AllocSet parameters.
 */
static ExprContext *
CreateExprContextInternal(EState *estate, Size minContextSize,
						  Size initBlockSize, Size maxBlockSize)
{
	ExprContext *econtext;
	MemoryContext oldcontext;

	/* Create the ExprContext node within the per-query memory context */
	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	econtext = makeNode(ExprContext);

	/* Initialize fields of ExprContext */
	econtext->ecxt_scantuple = NULL;
	econtext->ecxt_innertuple = NULL;
	econtext->ecxt_outertuple = NULL;

	econtext->ecxt_per_query_memory = estate->es_query_cxt;

	/*
	 * Create working memory for expression evaluation in this context.
	 */
	econtext->ecxt_per_tuple_memory =
		AllocSetContextCreate(estate->es_query_cxt,
							  "ExprContext",
							  minContextSize,
							  initBlockSize,
							  maxBlockSize);

	econtext->ecxt_param_exec_vals = estate->es_param_exec_vals;
	econtext->ecxt_param_list_info = estate->es_param_list_info;

	econtext->ecxt_aggvalues = NULL;
	econtext->ecxt_aggnulls = NULL;

	econtext->caseValue_datum = (Datum) 0;
	econtext->caseValue_isNull = true;

	econtext->domainValue_datum = (Datum) 0;
	econtext->domainValue_isNull = true;

	econtext->ecxt_estate = estate;

	econtext->ecxt_callbacks = NULL;

	/*
	 * Link the ExprContext into the EState to ensure it is shut down when the
	 * EState is freed.  Because we use lcons(), shutdowns will occur in
	 * reverse order of creation, which may not be essential but can't hurt.
	 */
	estate->es_exprcontexts = lcons(econtext, estate->es_exprcontexts);

	MemoryContextSwitchTo(oldcontext);

	return econtext;
}

/* ----------------