Fix non-ASCII column name case insensitivity

Author: mtopolnik

core/src/main/java/io/questdb/client/std/AbstractLowerCaseAsciiCharSequenceHashSet.java

@@ -54,13 +54,13 @@ public void clear() {
     }
 
     public int keyIndex(CharSequence key) {
-        int index = Chars.lowerCaseAsciiHashCode(key) & mask;
+        int index = Chars.lowerCaseHashCode(key) & mask;
 
         if (keys[index] == noEntryKey) {
             return index;
         }
 
-        if (Chars.equalsLowerCaseAscii(key, keys[index])) {
+        if (Chars.equalsIgnoreCase(key, keys[index])) {
             return -index - 1;
         }
 
@@ -77,7 +77,7 @@ private int probe(CharSequence key, int index) {
             if (keys[index] == noEntryKey) {
                 return index;
             }
-            if (Chars.equalsLowerCaseAscii(key, keys[index])) {
+            if (Chars.equalsIgnoreCase(key, keys[index])) {
                 return -index - 1;
             }
         } while (true);

core/src/main/java/io/questdb/client/std/Chars.java

@@ -364,6 +364,22 @@ public static boolean startsWith(CharSequence _this, char c) {
         return _this.length() > 0 && _this.charAt(0) == c;
     }
 
+    public static String toLowerCase(@Nullable CharSequence value) {
+        if (value == null) {
+            return null;
+        }
+        final int len = value.length();
+        if (len == 0) {
+            return "";
+        }
+
+        final Utf16Sink b = Misc.getThreadLocalSink();
+        for (int i = 0; i < len; i++) {
+            b.put(Character.toLowerCase(value.charAt(i)));
+        }
+        return b.toString();
+    }
+
     public static String toLowerCaseAscii(@Nullable CharSequence value) {
         if (value == null) {
             return null;

core/src/main/java/io/questdb/client/std/LowerCaseAsciiCharSequenceIntHashMap.java

@@ -65,14 +65,14 @@ public boolean putAt(int index, CharSequence key, int value) {
             values[-index - 1] = value;
             return false;
         }
-        putAt0(index, Chars.toLowerCaseAscii(key), value);
+        putAt0(index, Chars.toLowerCase(key), value);
         return true;
     }
 
     public void putIfAbsent(CharSequence key, int value) {
         int index = keyIndex(key);
         if (index > -1) {
-            putAt0(index, Chars.toLowerCaseAscii(key), value);
+            putAt0(index, Chars.toLowerCase(key), value);
         }
     }