Function hashagg_recompile_expressions

src/backend/executor/nodeAgg.c:1801–1848

* hashagg_recompile_expressions() * * Identifies the right phase, compiles the right expression given the * arguments, and then sets phase->evalfunc to that expression. * * Different versions of the compiled expression are needed depending on * whether hash aggregation has spilled or not, and whether it's reading from * the outer plan or a tape. Before spilling to disk, the expression reads

 * expressions in the AggStatePerPhase, and reuse when appropriate.
 */
static void
hashagg_recompile_expressions(AggState *aggstate, bool minslot, bool nullcheck)
{
	AggStatePerPhase phase;
	int			i = minslot ? 1 : 0;
	int			j = nullcheck ? 1 : 0;

	Assert(aggstate->aggstrategy == AGG_HASHED ||
		   aggstate->aggstrategy == AGG_MIXED);

	if (aggstate->aggstrategy == AGG_HASHED)
		phase = &aggstate->phases[0];
	else						/* AGG_MIXED */
		phase = &aggstate->phases[1];

	if (phase->evaltrans_cache[i][j] == NULL)
	{
		const TupleTableSlotOps *outerops = aggstate->ss.ps.outerops;
		bool		outerfixed = aggstate->ss.ps.outeropsfixed;
		bool		dohash = true;
		bool		dosort = false;

		/*
		 * If minslot is true, that means we are processing a spilled batch
		 * (inside agg_refill_hash_table()), and we must not advance the
		 * sorted grouping sets.
		 */
		if (aggstate->aggstrategy == AGG_MIXED && !minslot)
			dosort = true;

		/* temporarily change the outerops while compiling the expression */
		if (minslot)
		{
			aggstate->ss.ps.outerops = &TTSOpsMinimalTuple;
			aggstate->ss.ps.outeropsfixed = true;
		}

		phase->evaltrans_cache[i][j] = ExecBuildAggTrans(aggstate, phase,
														 dosort, dohash,
														 nullcheck);

		/* change back */
		aggstate->ss.ps.outerops = outerops;
		aggstate->ss.ps.outeropsfixed = outerfixed;
	}

	phase->evaltrans = phase->evaltrans_cache[i][j];
}

/*
 * Set limits that trigger spilling to avoid exceeding hash_mem. Consider the