Improvement #7038 - Improve performance of STARTING WITH of fixed-byt…

…e charsets with insensitive collations.

src/jrd/Collation.cpp

@@ -444,15 +444,17 @@ template <typename CharType, typename StrConverter>
 class StartsMatcher : public PatternMatcher
 {
 public:
-	StartsMatcher(MemoryPool& pool, TextType* ttype, const CharType* str, SLONG str_len)
+	StartsMatcher(MemoryPool& pool, TextType* ttype, const CharType* str, SLONG str_len, SLONG aPatternByteLength)
 		: PatternMatcher(pool, ttype),
-		  evaluator(pool, str, str_len)
+		  evaluator(pool, str, str_len),
+		  patternByteLength(ttype->getCharSet()->isMultiByte() ? -1 : aPatternByteLength)
 	{
 	}
 
 	void reset()
 	{
 		evaluator.reset();
+		processedByteLength = 0;
 	}
 
 	bool result()
@@ -462,36 +464,57 @@ class StartsMatcher : public PatternMatcher
 
 	bool process(const UCHAR* str, SLONG length)
 	{
+		if (patternByteLength != -1)
+		{
+			if (processedByteLength + length > patternByteLength)
+				length = patternByteLength - processedByteLength;
+		}
+
+		processedByteLength += length;
+
 		StrConverter cvt(pool, textType, str, length);
 		fb_assert(length % sizeof(CharType) == 0);
+
 		return evaluator.processNextChunk(
 			reinterpret_cast<const CharType*>(str), length / sizeof(CharType));
 	}
 
 	static StartsMatcher* create(MemoryPool& pool, TextType* ttype,
 		const UCHAR* str, SLONG length)
 	{
+		const auto patternByteLength = length;
+
 		StrConverter cvt(pool, ttype, str, length);
 		fb_assert(length % sizeof(CharType) == 0);
+
 		return FB_NEW_POOL(pool) StartsMatcher(pool, ttype,
-			reinterpret_cast<const CharType*>(str), length / sizeof(CharType));
+			reinterpret_cast<const CharType*>(str), length / sizeof(CharType), patternByteLength);
 	}
 
 	static bool evaluate(MemoryPool& pool, TextType* ttype, const UCHAR* s, SLONG sl,
 		const UCHAR* p, SLONG pl)
 	{
+		if (!ttype->getCharSet()->isMultiByte() && sl > pl)
+			sl = pl;
+
 		StrConverter cvt1(pool, ttype, p, pl);
-		StrConverter cvt2(pool, ttype, s, sl);
 		fb_assert(pl % sizeof(CharType) == 0);
+
+		StrConverter cvt2(pool, ttype, s, sl);
 		fb_assert(sl % sizeof(CharType) == 0);
+
 		Firebird::StartsEvaluator<CharType> evaluator(pool,
 			reinterpret_cast<const CharType*>(p), pl / sizeof(CharType));
+
 		evaluator.processNextChunk(reinterpret_cast<const CharType*>(s), sl / sizeof(CharType));
+
 		return evaluator.getResult();
 	}
 
 private:
 	Firebird::StartsEvaluator<CharType> evaluator;
+	const SLONG patternByteLength;	// -1 used for MBCS and not optimize things
+	SLONG processedByteLength = 0;
 };
 
 template <typename CharType, typename StrConverter = CanonicalConverter<UpcaseConverter<> > >