Fixed CORE-1040: Wrong single-segment ascending index on character fi…

…eld with NULL and empty string values
FirebirdSQL · Dec 6, 2006 · a211ffc · a211ffc
1 parent 2fefa99
commit a211ffc
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Showing 2 changed files with 20 additions and 2 deletions.
diff --git a/src/jrd/btr.cpp b/src/jrd/btr.cpp
@@ -3161,6 +3161,10 @@ static SLONG fast_load(thread_db* tdbb,
 	duplicatesList.grow(segments);
 	memset(duplicatesList.begin(), 0, segments * sizeof(ULONG));
 
+	// hvlad: look at IDX_create_index for explanations about NULL indicator below
+	const bool isODS11 = (dbb->dbb_ods_version >= ODS_VERSION11);
+	const int nullIndLen = isODS11 && !descending && (idx->idx_count == 1) ? 1 : 0;
+
 	try {
 
 		// If there's an error during index construction, fall
@@ -3202,6 +3206,7 @@ static SLONG fast_load(thread_db* tdbb,
 			}
 			index_sort_record* isr = (index_sort_record*) (record + key_length);
 			count++;
+			record += nullIndLen;
 
 			// restore previous values
 			bucket = buckets[0];

diff --git a/src/jrd/idx.cpp b/src/jrd/idx.cpp
@@ -256,7 +256,17 @@ void IDX_create_index(
 	const bool isDescending = (idx->idx_flags & idx_descending);
 	const bool isPrimary = (idx->idx_flags & idx_primary);
 
-	const USHORT key_length = ROUNDUP(BTR_key_length(tdbb, relation, idx), sizeof(SLONG));
+	// hvlad: in ODS11 empty string and NULL values can have the same binary 
+	// representation in index keys. BTR can distinguish it by the key_length 
+	// but SORT module currently don't take it into account. Therefore add to 
+	// the index key one byte prefix with 0 for NULL value and 1 for not-NULL 
+	// value to produce right sorting.
+	// BTR\fast_load will remove this one byte prefix from the index key.
+	// Note that this is necessary only for single-segment ascending indexes 
+	// and only for ODS11 and higer.
+
+	const int nullIndLen = isODS11 && !isDescending && (idx->idx_count == 1) ? 1 : 0;
+	const USHORT key_length = ROUNDUP(BTR_key_length(tdbb, relation, idx) + nullIndLen, sizeof(SLONG));
 
 	const USHORT max_key_size =
 		isODS11 ? MAX_KEY_LIMIT : MAX_KEY_PRE_ODS11;
@@ -459,11 +469,14 @@ void IDX_create_index(
 
 			USHORT l = key.key_length;
 
+			if (nullIndLen) {
+				*p++ = (key.key_length == 0) ? 0 : 1;
+			}
 			if (l > 0) {
 				memcpy(p, key.key_data, l);
 				p += l;
 			}
-			if ( (l = key_length - key.key_length) ) {
+			if ( (l = key_length - nullIndLen - key.key_length) ) {
 				memset(p, pad, l);
 				p += l;
 			}