1) Extended hash joins to handle more than two streams at once.

2) Allowed the hash table size to be configurable at runtime.

src/jrd/recsrc/HashJoin.cpp

@@ -37,17 +37,140 @@ using namespace Jrd;
 // Data access: hash join
 // ----------------------
 
-HashJoin::HashJoin(CompilerScratch* csb, RecordSource* outer, RecordSource* inner,
-				   const jrd_nod* outerKeys, const jrd_nod* innerKeys)
-	: m_outer(outer), m_inner(FB_NEW(csb->csb_pool) BufferedStream(csb, inner)),
-	  m_outerKeys(outerKeys), m_innerKeys(innerKeys),
+class HashJoin::HashTable : public PermanentStorage
+{
+	static const size_t HASH_SIZE = 1009;
+
+	typedef Firebird::Array<FB_UINT64> CollisionList;
+
+public:
+	HashTable(MemoryPool& pool, size_t streamCount, size_t tableSize = HASH_SIZE)
+		: PermanentStorage(pool), m_streamCount(streamCount), m_tableSize(tableSize), m_slot(0)
+	{
+		m_collisions = FB_NEW(pool) CollisionList*[streamCount * tableSize];
+		memset(m_collisions, 0, streamCount * tableSize * sizeof(CollisionList*));
+
+		m_iterators = FB_NEW(pool) size_t[streamCount];
+		memset(m_iterators, 0, streamCount * sizeof(size_t));
+	}
+
+	~HashTable()
+	{
+		for (size_t i = 0; i < m_streamCount * m_tableSize; i++)
+		{
+			delete m_collisions[i];
+		}
+
+		delete[] m_collisions;
+		delete[] m_iterators;
+	}
+
+	size_t hash(const UCHAR* address, size_t length)
+	{
+		size_t hash_value = 0;
+		UCHAR* p = NULL;
+		const UCHAR* q = address;
+		for (size_t l = 0; l < length; l++)
+		{
+			if (!(l & 3))
+			{
+				p = (UCHAR*) &hash_value;
+			}
+
+			*p++ += *q++;
+		}
+
+		return (hash_value % m_tableSize);
+	}
+
+	void put(size_t stream, size_t slot, FB_UINT64 value)
+	{
+		fb_assert(stream < m_streamCount);
+		fb_assert(slot < m_tableSize);
+
+		CollisionList* collisions = m_collisions[stream * m_streamCount + slot];
+
+		if (!collisions)
+		{
+			collisions = FB_NEW(getPool()) CollisionList(getPool());
+			m_collisions[stream * m_streamCount + slot] = collisions;
+		}
+
+		collisions->add(value);
+	}
+
+	bool setup(size_t slot)
+	{
+		fb_assert(slot < m_tableSize);
+
+		for (size_t i = 0; i < m_streamCount; i++)
+		{
+			if (!m_collisions[i * m_streamCount + slot])
+			{
+				return false;
+			}
+
+			reset(i);
+		}
+
+		m_slot = slot;
+		return true;
+	}
+
+	void reset(size_t stream)
+	{
+		fb_assert(stream < m_streamCount);
+
+		m_iterators[stream] = 0;
+	}
+
+	bool iterate(size_t stream, FB_UINT64& value)
+	{
+		fb_assert(stream < m_streamCount);
+
+		CollisionList* const collisions = m_collisions[stream * m_streamCount + m_slot];
+		size_t& iterator = m_iterators[stream];
+
+		if (iterator < collisions->getCount())
+		{
+			value = (*collisions)[iterator++];
+			return true;
+		}
+
+		return false;
+	}
+
+private:
+	const size_t m_streamCount;
+	const size_t m_tableSize;
+	CollisionList** m_collisions;
+	size_t* m_iterators;
+	size_t m_slot;
+};
+
+
+HashJoin::HashJoin(CompilerScratch* csb, size_t count,
+				   RecordSource* const* args, jrd_nod* const* keys)
+	: m_args(csb->csb_pool, count - 1), m_keys(csb->csb_pool, count - 1),
 	  m_outerJoin(false), m_semiJoin(false), m_antiJoin(false)
 {
-	fb_assert(m_outer && m_inner);
-	fb_assert(m_outerKeys && m_outerKeys->nod_type == nod_list);
-	fb_assert(m_innerKeys && m_innerKeys->nod_type == nod_list);
+	fb_assert(count >= 2);
 
 	m_impure = CMP_impure(csb, sizeof(Impure));
+
+	fb_assert(args[0]);
+	m_leader = args[0];
+	fb_assert(keys[0]);
+	m_leaderKeys = keys[0];
+
+	for (size_t i = 1; i < count; i++)
+	{
+		fb_assert(args[i]);
+		m_args.add(FB_NEW(csb->csb_pool) BufferedStream(csb, args[i]));
+
+		fb_assert(keys[i] && keys[i]->nod_type == nod_list);
+		m_keys.add(keys[i]);
+	}
 }
 
 void HashJoin::open(thread_db* tdbb)
@@ -57,59 +180,48 @@ void HashJoin::open(thread_db* tdbb)
 
 	impure->irsb_flags = irsb_open | irsb_mustread;
 
-	for (size_t i = 0; i < HASH_SIZE; i++)
+	delete impure->irsb_hash_table;
+	MemoryPool& pool = *tdbb->getDefaultPool();
+	impure->irsb_hash_table = FB_NEW(pool) HashTable(pool, m_args.getCount());
+
+	for (size_t i = 0; i < m_args.getCount(); i++)
 	{
-		delete impure->irsb_hash_table[i];
-		impure->irsb_hash_table[i] = NULL;
-	}
+		// Read and cache the inner streams. While doing that,
+		// hash the join condition values and populate hash tables.
 
-	// Read and cache the inner stream. While doing that,
-	// hash the join condition values and populate a hash table.
+		m_args[i]->open(tdbb);
 
-	m_inner->open(tdbb);
-	FB_UINT64 position = 0;
-
-	while (m_inner->getRecord(tdbb))
-	{
-		const USHORT hash_slot = hashKeys(tdbb, request, false);
-		CollisionList* collisions = impure->irsb_hash_table[hash_slot];
-
-		if (!collisions)
+		FB_UINT64 position = 0;
+		while (m_args[i]->getRecord(tdbb))
 		{
-			MemoryPool& pool = *tdbb->getDefaultPool();
-			collisions = FB_NEW(pool) CollisionList(pool);
-			impure->irsb_hash_table[hash_slot] = collisions;
+			const size_t hash_slot = hashKeys(tdbb, request, impure->irsb_hash_table, m_keys[i]);
+			impure->irsb_hash_table->put(i, hash_slot, position++);
 		}
-
-		collisions->add(position++);
 	}
 
-	impure->irsb_hash_slot = 0;
-	impure->irsb_collision = 0;
-
-	m_outer->open(tdbb);
+	m_leader->open(tdbb);
 }
 
 void HashJoin::close(thread_db* tdbb)
 {
 	jrd_req* const request = tdbb->getRequest();
+	Impure* const impure = (Impure*) ((UCHAR*) request + m_impure);
 
 	invalidateRecords(request);
 
-	Impure* const impure = (Impure*) ((UCHAR*) request + m_impure);
-
 	if (impure->irsb_flags & irsb_open)
 	{
 		impure->irsb_flags &= ~irsb_open;
 
-		for (size_t i = 0; i < HASH_SIZE; i++)
+		delete impure->irsb_hash_table;
+		impure->irsb_hash_table = NULL;
+
+		for (size_t i = 0; i < m_args.getCount(); i++)
 		{
-			delete impure->irsb_hash_table[i];
-			impure->irsb_hash_table[i] = NULL;
+			m_args[i]->close(tdbb);
 		}
 
-		m_outer->close(tdbb);
-		m_inner->close(tdbb);
+		m_leader->close(tdbb);
 	}
 }
 
@@ -127,39 +239,51 @@ bool HashJoin::getRecord(thread_db* tdbb)
 	{
 		if (impure->irsb_flags & irsb_mustread)
 		{
-			if (!m_outer->getRecord(tdbb))
+			// Fetch the record from the leading stream
+
+			if (!m_leader->getRecord(tdbb))
 			{
 				return false;
 			}
 
-			const USHORT hash_slot = hashKeys(tdbb, request, true);
+			// Hash the comparison keys
 
-			if (!impure->irsb_hash_table[hash_slot])
+			const size_t hash_slot = hashKeys(tdbb, request, impure->irsb_hash_table, m_leaderKeys);
+
+			// Ensure the every inner stream having matches for this hash slot.
+			// Setup the hash table for the iteration through collisions.
+
+			if (!impure->irsb_hash_table->setup(hash_slot))
 			{
 				continue;
 			}
 
-			impure->irsb_hash_slot = hash_slot;
-			impure->irsb_collision = 0;
 			impure->irsb_flags &= ~irsb_mustread;
+			impure->irsb_flags |= irsb_first;
 		}
 
-		CollisionList* const collisions = impure->irsb_hash_table[impure->irsb_hash_slot];
+		// Fetch collisions from the inner streams
 
-		if (impure->irsb_collision >= collisions->getCount())
+		if (impure->irsb_flags & irsb_first)
+		{
+			for (size_t i = 0; i < m_args.getCount(); i++)
+			{
+				if (!fetchRecord(tdbb, impure->irsb_hash_table, i))
+				{
+					fb_assert(false);
+					return false;
+				}
+			}
+
+			impure->irsb_flags &= ~irsb_first;
+		}
+		else if (!fetchRecord(tdbb, impure->irsb_hash_table, m_args.getCount() - 1))
 		{
 			impure->irsb_flags |= irsb_mustread;
 			continue;
 		}
 
-		const FB_UINT64 position = (*collisions)[impure->irsb_collision++];
-		m_inner->locate(tdbb, position);
-
-		if (!m_inner->getRecord(tdbb))
-		{
-			fb_assert(false);
-			return false;
-		}
+		// Ensure that the comparison keys are really equal
 
 		if (compareKeys(tdbb, request))
 		{
@@ -188,63 +312,85 @@ void HashJoin::dump(thread_db* tdbb, UCharBuffer& buffer)
 	buffer.add(isc_info_rsb_type);
 	buffer.add(isc_info_rsb_hash);
 
-	buffer.add(2);
+	const size_t count = m_args.getCount() + 1;
+	// This place must be reviewed if we allow more than 255 joins
+	fb_assert(count <= USHORT(MAX_UCHAR));
+	buffer.add((UCHAR) count);
 
-	m_outer->dump(tdbb, buffer);
-	m_inner->dump(tdbb, buffer);
+	m_leader->dump(tdbb, buffer);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->dump(tdbb, buffer);
+	}
 
 	buffer.add(isc_info_rsb_end);
 }
 
 void HashJoin::markRecursive()
 {
-	m_outer->markRecursive();
-	m_inner->markRecursive();
+	m_leader->markRecursive();
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->markRecursive();
+	}
 }
 
 void HashJoin::findUsedStreams(StreamsArray& streams)
 {
-	m_outer->findUsedStreams(streams);
-	m_inner->findUsedStreams(streams);
+	m_leader->findUsedStreams(streams);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->findUsedStreams(streams);
+	}
 }
 
 void HashJoin::invalidateRecords(jrd_req* request)
 {
-	m_outer->invalidateRecords(request);
-	m_inner->invalidateRecords(request);
+	m_leader->invalidateRecords(request);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->invalidateRecords(request);
+	}
 }
 
 void HashJoin::nullRecords(thread_db* tdbb)
 {
-	m_outer->nullRecords(tdbb);
-	m_inner->nullRecords(tdbb);
+	m_leader->nullRecords(tdbb);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->nullRecords(tdbb);
+	}
 }
 
 void HashJoin::saveRecords(thread_db* tdbb)
 {
-	m_outer->saveRecords(tdbb);
-	m_inner->saveRecords(tdbb);
+	m_leader->saveRecords(tdbb);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->saveRecords(tdbb);
+	}
 }
 
 void HashJoin::restoreRecords(thread_db* tdbb)
 {
-	m_outer->restoreRecords(tdbb);
-	m_inner->restoreRecords(tdbb);
+	m_leader->restoreRecords(tdbb);
+	for (size_t i = 0; i < m_args.getCount(); i++)
+	{
+		m_args[i]->restoreRecords(tdbb);
+	}
 }
 
-USHORT HashJoin::hashKeys(thread_db* tdbb, jrd_req* request, bool outer)
+size_t HashJoin::hashKeys(thread_db* tdbb, jrd_req* request, HashTable* table, jrd_nod* keys)
 {
-	const jrd_nod* const list = outer ? m_outerKeys : m_innerKeys;
+	size_t hash_slot = 0;
 
-	ULONG hash_value = 0;
-
-	for (size_t i = 0; i < list->nod_count; i++)
+	for (size_t i = 0; i < keys->nod_count; i++)
 	{
-		const dsc* const desc = EVL_expr(tdbb, list->nod_arg[i]);
+		const dsc* const desc = EVL_expr(tdbb, keys->nod_arg[i]);
 
 		if (desc && !(request->req_flags & req_null))
 		{
-			USHORT length = desc->dsc_length;
+			size_t length = desc->dsc_length;
 			const UCHAR* address = desc->dsc_address;
 
 			if (desc->dsc_dtype == dtype_varying)
@@ -258,43 +404,72 @@ USHORT HashJoin::hashKeys(thread_db* tdbb, jrd_req* request, bool outer)
 				length = strlen((char*) address);
 			}
 
-			UCHAR* p = NULL;
-			const UCHAR* q = address;
-			for (USHORT l = 0; l < length; l++)
-			{
-				if (!(l & 3))
-				{
-					p = (UCHAR*) &hash_value;
-				}
-
-				*p++ += *q++;
-			}
+			hash_slot ^= table->hash(address, length);
 		}
 	}
 
-	return (USHORT) (hash_value % HASH_SIZE);
+	return hash_slot;
 }
 
 bool HashJoin::compareKeys(thread_db* tdbb, jrd_req* request)
 {
-	for (size_t i = 0; i < m_outerKeys->nod_count; i++)
+	for (size_t i = 0; i < m_leaderKeys->nod_count; i++)
 	{
-		const dsc* const desc1 = EVL_expr(tdbb, m_outerKeys->nod_arg[i]);
+		const dsc* const desc1 = EVL_expr(tdbb, m_leaderKeys->nod_arg[i]);
 		const bool null1 = (request->req_flags & req_null);
 
-		const dsc* const desc2 = EVL_expr(tdbb, m_innerKeys->nod_arg[i]);
-		const bool null2 = (request->req_flags & req_null);
-
-		if (null1 != null2)
+		for (size_t j = 0; j < m_keys.getCount(); j++)
 		{
-			return false;
-		}
+			const dsc* const desc2 = EVL_expr(tdbb, m_keys[j]->nod_arg[i]);
+			const bool null2 = (request->req_flags & req_null);
 
-		if (!null1 && !null2 && MOV_compare(desc1, desc2) != 0)
-		{
-			return false;
+			if (null1 != null2)
+			{
+				return false;
+			}
+
+			if (!null1 && !null2 && MOV_compare(desc1, desc2) != 0)
+			{
+				return false;
+			}
 		}
 	}
 
 	return true;
 }
+
+bool HashJoin::fetchRecord(thread_db* tdbb, HashTable* table, size_t stream)
+{
+	BufferedStream* const arg = m_args[stream];
+	FB_UINT64 position;
+
+	if (table->iterate(stream, position))
+	{
+		arg->locate(tdbb, position);
+
+		if (arg->getRecord(tdbb))
+		{
+			return true;
+		}
+	}
+
+	while (true)
+	{
+		if (stream == 0 || !fetchRecord(tdbb, table, stream - 1))
+		{
+			return false;
+		}
+
+		table->reset(stream);
+
+		if (table->iterate(stream, position))
+		{
+			arg->locate(tdbb, position);
+
+			if (arg->getRecord(tdbb))
+			{
+				return true;
+			}
+		}
+	}
+}

src/jrd/recsrc/RecordSource.h

@@ -750,19 +750,16 @@ namespace Jrd
 
 	class HashJoin : public RecordSource
 	{
-		static const size_t HASH_SIZE = 1009;
-		typedef Firebird::Array<FB_UINT64> CollisionList;
+		class HashTable;
 
 		struct Impure : public RecordSource::Impure
 		{
-			CollisionList* irsb_hash_table[HASH_SIZE];
-			USHORT irsb_hash_slot;
-			size_t irsb_collision;
+			HashTable* irsb_hash_table;
 		};
 
 	public:
-		HashJoin(CompilerScratch* csb, RecordSource* outer, RecordSource* inner,
-				 const jrd_nod* outerKeys, const jrd_nod* innerKeys);
+		HashJoin(CompilerScratch* csb, size_t count,
+				 RecordSource* const* args, jrd_nod* const* keys);
 
 		void open(thread_db* tdbb);
 		void close(thread_db* tdbb);
@@ -782,13 +779,14 @@ namespace Jrd
 		void restoreRecords(thread_db* tdbb);
 
 	private:
-		USHORT hashKeys(thread_db* tdbb, jrd_req* request, bool outer);
+		size_t hashKeys(thread_db* tdbb, jrd_req* request, HashTable* table, jrd_nod* keys);
 		bool compareKeys(thread_db* tdbb, jrd_req* request);
+		bool fetchRecord(thread_db* tdbb, HashTable* table, size_t stream);
 
-		RecordSource* const m_outer;
-		BufferedStream* const m_inner;
-		const jrd_nod* const m_outerKeys;
-		const jrd_nod* const m_innerKeys;
+		RecordSource* m_leader;
+		jrd_nod* m_leaderKeys;
+		Firebird::Array<BufferedStream*> m_args;
+		Firebird::Array<jrd_nod*> m_keys;
 		const bool m_outerJoin;
 		const bool m_semiJoin;
 		const bool m_antiJoin;