Function ExecHashJoinNewBatch

src/backend/executor/nodeHashjoin.c:1253–1416

* ExecHashJoinNewBatch * switch to a new hashjoin batch * * Returns true if successful, false if there are no more batches. */

 * Returns true if successful, false if there are no more batches.
 */
static bool
ExecHashJoinNewBatch(HashJoinState *hjstate)
{
	HashJoinTable hashtable = hjstate->hj_HashTable;
	int			nbatch;
	int			curbatch;

	SIMPLE_FAULT_INJECTOR("exec_hashjoin_new_batch");

	HashState  *hashState = (HashState *) innerPlanState(hjstate);

	nbatch = hashtable->nbatch;
	curbatch = hashtable->curbatch;

	if (curbatch >= nbatch)
		return false;

	if (curbatch >= 0 && hashtable->stats)
		ExecHashTableExplainBatchEnd(hashState, hashtable);

	if (curbatch > 0)
	{
		/*
		 * We no longer need the previous outer batch file; close it right
		 * away to free disk space.
		 */
		if (hashtable->outerBatchFile[curbatch])
			BufFileClose(hashtable->outerBatchFile[curbatch]);
		hashtable->outerBatchFile[curbatch] = NULL;
	}
	else						/* we just finished the first batch */
	{
		/*
		 * Reset some of the skew optimization state variables, since we no
		 * longer need to consider skew tuples after the first batch. The
		 * memory context reset we are about to do will release the skew
		 * hashtable itself.
		 */
		hashtable->skewEnabled = false;
		hashtable->skewBucket = NULL;
		hashtable->skewBucketNums = NULL;
		hashtable->nSkewBuckets = 0;
		hashtable->spaceUsedSkew = 0;
	}

	/*
	 * If we want to keep the hash table around, for re-scan, then write
	 * the current batch's state to disk before moving to the next one.
	 * It's possible that we increase the number of batches later, so that
	 * by the time we reload this file, some of the tuples we wrote here
	 * will logically belong to a later file. ExecHashJoinReloadHashTable
	 * will move such tuples when the file is reloaded.
	 *
	 * If we have already re-scanned, we might still have the old file
	 * around, in which case there's no need to write it again.
	 * XXX: Currently, we actually always re-create it, see comments in
	 * ExecHashJoinReloadHashTable.
	 */