Renaem nullable -> use/hasNullBitmap

"Nullable" is a confusing concept due to QuestDB null sentinels, which
means a "non-nullable" column could still hold nulls via sentinel
values.

Author: mtopolnik

core/src/main/java/io/questdb/client/cutlass/qwp/client/QwpColumnWriter.java

@@ -58,7 +58,7 @@ private void encodeColumn(
     ) {
         long dataAddr = col.getDataAddress();
 
-        if (colDef.isNullable()) {
+        if (colDef.hasNullBitmap()) {
             writeNullBitmap(col, rowCount);
         }
 

core/src/main/java/io/questdb/client/cutlass/qwp/client/QwpUdpSender.java

@@ -703,7 +703,7 @@ private static int utf8Length(CharSequence s) {
         return len;
     }
 
-    private QwpTableBuffer.ColumnBuffer acquireColumn(CharSequence name, byte type, boolean nullable) {
+    private QwpTableBuffer.ColumnBuffer acquireColumn(CharSequence name, byte type, boolean useNullBitmap) {
         QwpTableBuffer.ColumnBuffer col = currentTableBuffer.getExistingColumn(name, type);
         if (col == null && currentTableBuffer.getRowCount() > 0) {
             // schema change while having some rows accumulated -> we flush committed rows of the current table
@@ -718,7 +718,7 @@ private QwpTableBuffer.ColumnBuffer acquireColumn(CharSequence name, byte type,
         }
 
         if (col == null) {
-            col = currentTableBuffer.getOrCreateColumn(name, type, nullable);
+            col = currentTableBuffer.getOrCreateColumn(name, type, useNullBitmap);
         }
         return col;
     }
@@ -1043,7 +1043,7 @@ private long estimateCurrentDatagramSizeWithInProgressRow(int targetRows) {
         for (int i = 0; i < inProgressColumnCount; i++) {
             InProgressColumnState state = inProgressColumns[i];
             estimate += state.payloadEstimateDelta;
-            if (state.nullable) {
+            if (state.useNullBitmap) {
                 estimate += bitmapBytes(targetRows) - bitmapBytes(state.sizeBefore);
             }
         }
@@ -1343,7 +1343,7 @@ private static final class InProgressColumnState {
         private int arrayDataOffsetBefore;
         private int arrayShapeOffsetBefore;
         private QwpTableBuffer.ColumnBuffer column;
-        private boolean nullable;
+        private boolean useNullBitmap;
         private long payloadEstimateDelta;
         private int sizeBefore;
         private long stringDataSizeBefore;
@@ -1356,13 +1356,13 @@ void captureAfterWrite() {
 
         void clear() {
             column = null;
-            nullable = false;
+            useNullBitmap = false;
             payloadEstimateDelta = 0;
         }
 
         void of(QwpTableBuffer.ColumnBuffer column) {
             this.column = column;
-            this.nullable = column.usesNullBitmap();
+            this.useNullBitmap = column.usesNullBitmap();
             this.payloadEstimateDelta = 0;
             this.sizeBefore = column.getSize();
             this.valueCountBefore = column.getValueCount();

core/src/main/java/io/questdb/client/cutlass/qwp/protocol/QwpColumnDef.java

@@ -34,33 +34,33 @@
  */
 public final class QwpColumnDef {
     private final String name;
-    private final boolean nullable;
+    private final boolean hasNullBitmap;
     private final byte typeCode;
 
     /**
      * Creates a column definition.
      *
      * @param name     the column name (UTF-8)
-     * @param typeCode the QWP v1 type code (0x01-0x0F, optionally OR'd with 0x80 for nullable)
+     * @param typeCode the QWP v1 type code (0x01-0x0F, optionally OR'd with 0x80 for null bitmap)
      */
     public QwpColumnDef(String name, byte typeCode) {
         this.name = name;
-        // Extract nullable flag (high bit) and base type
-        this.nullable = (typeCode & 0x80) != 0;
+        // Extract null bitmap flag (high bit) and base type
+        this.hasNullBitmap = (typeCode & 0x80) != 0;
         this.typeCode = (byte) (typeCode & 0x7F);
     }
 
     /**
-     * Creates a column definition with explicit nullable flag.
+     * Creates a column definition with explicit null bitmap flag.
      *
-     * @param name     the column name
-     * @param typeCode the base type code (0x01-0x0F)
-     * @param nullable whether the column is nullable
+     * @param name           the column name
+     * @param typeCode       the base type code (0x01-0x0F)
+     * @param hasNullBitmap  whether the column has a null bitmap
      */
-    public QwpColumnDef(String name, byte typeCode, boolean nullable) {
+    public QwpColumnDef(String name, byte typeCode, boolean hasNullBitmap) {
         this.name = name;
         this.typeCode = (byte) (typeCode & 0x7F);
-        this.nullable = nullable;
+        this.hasNullBitmap = hasNullBitmap;
     }
 
     @Override
@@ -69,7 +69,7 @@ public boolean equals(Object o) {
         if (o == null || getClass() != o.getClass()) return false;
         QwpColumnDef that = (QwpColumnDef) o;
         return typeCode == that.typeCode &&
-                nullable == that.nullable &&
+                hasNullBitmap == that.hasNullBitmap &&
                 name.equals(that.name);
     }
 
@@ -81,7 +81,7 @@ public String getName() {
     }
 
     /**
-     * Gets the base type code (without nullable flag).
+     * Gets the base type code (without null bitmap flag).
      *
      * @return type code 0x01-0x0F
      */
@@ -97,34 +97,34 @@ public String getTypeName() {
     }
 
     /**
-     * Gets the wire type code (with nullable flag if applicable).
+     * Gets the wire type code (with null bitmap flag if applicable).
      *
      * @return type code as sent on wire
      */
     public byte getWireTypeCode() {
-        return nullable ? (byte) (typeCode | 0x80) : typeCode;
+        return hasNullBitmap ? (byte) (typeCode | 0x80) : typeCode;
     }
 
     @Override
     public int hashCode() {
         int result = name.hashCode();
         result = 31 * result + typeCode;
-        result = 31 * result + (nullable ? 1 : 0);
+        result = 31 * result + (hasNullBitmap ? 1 : 0);
         return result;
     }
 
     /**
-     * Returns true if this column is nullable.
+     * Returns true if this column has a null bitmap.
      */
-    public boolean isNullable() {
-        return nullable;
+    public boolean hasNullBitmap() {
+        return hasNullBitmap;
     }
 
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append(name).append(':').append(getTypeName());
-        if (nullable) {
+        if (hasNullBitmap) {
             sb.append('?');
         }
         return sb.toString();

core/src/main/java/io/questdb/client/cutlass/qwp/protocol/QwpConstants.java

@@ -309,7 +309,7 @@ public static int getFixedTypeSize(byte typeCode) {
      */
     public static String getTypeName(byte typeCode) {
         int code = typeCode & TYPE_MASK;
-        boolean nullable = (typeCode & TYPE_NULLABLE_FLAG) != 0;
+        boolean hasNullBitmap = (typeCode & TYPE_NULLABLE_FLAG) != 0;
         String name;
         switch (code) {
             case TYPE_BOOLEAN:
@@ -382,7 +382,7 @@ public static String getTypeName(byte typeCode) {
                 name = "UNKNOWN(" + code + ")";
                 break;
         }
-        return nullable ? name + "?" : name;
+        return hasNullBitmap ? name + "?" : name;
     }
 
     /**

core/src/main/java/io/questdb/client/cutlass/qwp/protocol/QwpSchemaHash.java

@@ -152,7 +152,7 @@ public static long computeSchemaHashDirect(io.questdb.client.std.ObjList<QwpTabl
                     hasher.update((byte) (0x80 | (c & 0x3F)));
                 }
             }
-            // Wire type code: type | (nullable ? 0x80 : 0)
+            // Wire type code: type | (useNullBitmap ? 0x80 : 0)
             byte wireType = (byte) (col.getType() | (col.useNullBitmap ? 0x80 : 0));
             hasher.update(wireType);
         }

core/src/main/java/io/questdb/client/cutlass/qwp/protocol/QwpTableBuffer.java

@@ -205,7 +205,7 @@ public ColumnBuffer getExistingColumn(CharSequence name, byte type) {
      * semantics.  The check is a single field comparison on the hot path and has
      * no measurable cost.
      */
-    public ColumnBuffer getOrCreateColumn(CharSequence name, byte type, boolean nullable) {
+    public ColumnBuffer getOrCreateColumn(CharSequence name, byte type, boolean useNullBitmap) {
         if (name == null || name.length() == 0) {
             throw new LineSenderException("column name cannot be empty");
         }
@@ -217,7 +217,7 @@ public ColumnBuffer getOrCreateColumn(CharSequence name, byte type, boolean null
             return existing.size <= rowCount ? existing : null;
         }
         if (TableUtils.isValidColumnName(name, MAX_COLUMN_NAME_LENGTH)) {
-            return createColumn(name, type, nullable);
+            return createColumn(name, type, useNullBitmap);
         }
         throw new LineSenderException(
                 name.length() > MAX_COLUMN_NAME_LENGTH ? "column name too long [maxLength=" + MAX_COLUMN_NAME_LENGTH + "]"
@@ -361,8 +361,8 @@ private static void assertColumnType(CharSequence name, byte type, ColumnBuffer
         }
     }
 
-    private ColumnBuffer createColumn(CharSequence name, byte type, boolean nullable) {
-        ColumnBuffer col = new ColumnBuffer(Chars.toString(name), type, nullable);
+    private ColumnBuffer createColumn(CharSequence name, byte type, boolean useNullBitmap) {
+        ColumnBuffer col = new ColumnBuffer(Chars.toString(name), type, useNullBitmap);
         col.sender = sender;
         int index = columns.size();
         col.index = index;

core/src/test/java/io/questdb/client/test/cutlass/qwp/client/DeltaSymbolDictionaryTest.java

@@ -184,7 +184,7 @@ public void testEdgeCase_nullSymbolValues() throws Exception {
             GlobalSymbolDictionary globalDict = new GlobalSymbolDictionary();
 
             try (QwpTableBuffer batch = new QwpTableBuffer("test")) {
-                QwpTableBuffer.ColumnBuffer col = batch.getOrCreateColumn("sym", TYPE_SYMBOL, true);  // nullable
+                QwpTableBuffer.ColumnBuffer col = batch.getOrCreateColumn("sym", TYPE_SYMBOL, true);  // useNullBitmap
 
                 int aaplId = globalDict.getOrAddSymbol("AAPL");
                 col.addSymbolWithGlobalId("AAPL", aaplId);

core/src/test/java/io/questdb/client/test/cutlass/qwp/client/QwpUdpSenderTest.java

@@ -2164,7 +2164,7 @@ private void decodeBooleans(Object[] values, boolean[] nulls, int valueCount) {
         }
 
         private ColumnValues decodeColumn(QwpColumnDef def, int rowCount) {
-            boolean[] nulls = def.isNullable() ? reader.readNullBitmap(rowCount) : new boolean[rowCount];
+            boolean[] nulls = def.hasNullBitmap() ? reader.readNullBitmap(rowCount) : new boolean[rowCount];
             int valueCount = rowCount - countNulls(nulls);
             Object[] values = new Object[rowCount];
 

core/src/test/java/io/questdb/client/test/cutlass/qwp/protocol/QwpColumnDefTest.java

@@ -80,7 +80,7 @@ public void testValidateNullableCharType() {
         byte nullableChar = (byte) (QwpConstants.TYPE_CHAR | QwpConstants.TYPE_NULLABLE_FLAG);
         QwpColumnDef col = new QwpColumnDef("ch", nullableChar);
         col.validate();
-        assertTrue(col.isNullable());
+        assertTrue(col.hasNullBitmap());
         assertEquals(QwpConstants.TYPE_CHAR, col.getTypeCode());
     }