Extend support of multiple columns in fulltext index (#25337)

Author: kunga

.github/last_commit.txt

@@ -1 +1 @@
-ee3cb799508e266feaecb150d9baf075dd586714
+9c1b4170d6c376675a5384e54d06d3cc74eaabe4

src/api/protos/ydb_table.proto

@@ -244,8 +244,9 @@ message FulltextIndexSettings {
     optional Layout layout = 1;
 
     // List of columns and their fulltext settings
-    // Currently, this list should contain a single entry
-    // And provided column should be the only one in the TableIndex.index_columns list
+    // Currently, this list should contain a single entry with specified analyzers
+    // Later, some columns may not use analyzers and will be indexed as-is
+    // This list must always match TableIndex.index_columns
     repeated ColumnAnalyzers columns = 2;
 }