Drop dangling TYPE_STRING references

The previous merge (#12) removed TYPE_STRING from QwpConstants but left
references in the decoder hot paths and one example. Replace the
TYPE_STRING || TYPE_VARCHAR unions with TYPE_VARCHAR alone, drop the
TYPE_STRING entry from the symbol-vs-varchar dispatch in
getColumnValue/lookupStringBytes, and update the hardening test + the
TypedResultExample to advertise/consume TYPE_VARCHAR on the wire.

The module now compiles and all QWP decoder/table-buffer tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: bluestreak01

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

@@ -403,7 +403,7 @@ public Object getValue(int col, int row) {
         if (wt == QwpConstants.TYPE_BOOLEAN) return getBool(col, row);
         if (wt == QwpConstants.TYPE_FLOAT) return getFloat(col, row);
         if (wt == QwpConstants.TYPE_DOUBLE) return getDouble(col, row);
-        if (wt == QwpConstants.TYPE_STRING || wt == QwpConstants.TYPE_SYMBOL) return getString(col, row);
+        if (wt == QwpConstants.TYPE_SYMBOL) return getString(col, row);
         if (wt == QwpConstants.TYPE_VARCHAR) return getVarchar(col, row);
         if (wt == QwpConstants.TYPE_UUID || wt == QwpConstants.TYPE_DECIMAL128
                 || wt == QwpConstants.TYPE_LONG256 || wt == QwpConstants.TYPE_DECIMAL256) {
@@ -562,7 +562,7 @@ private DirectUtf8Sequence lookupStringBytes(int col, int row, DirectUtf8String
         QwpColumnLayout l = columnLayouts.getQuick(col);
         byte wt = l.info.wireType;
         int denseIdx = l.denseIndex(row);
-        if (wt == QwpConstants.TYPE_STRING || wt == QwpConstants.TYPE_VARCHAR) {
+        if (wt == QwpConstants.TYPE_VARCHAR) {
             int startOff = Unsafe.getUnsafe().getInt(l.valuesAddr + 4L * denseIdx);
             int endOff = Unsafe.getUnsafe().getInt(l.valuesAddr + 4L * (denseIdx + 1));
             return view.of(l.stringBytesAddr + startOff, l.stringBytesAddr + endOff);

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

@@ -584,9 +584,8 @@ private long parseColumn(QwpColumnLayout layout, int rowCount, long p, long limi
             layout.info.scale = Unsafe.getUnsafe().getByte(p++) & 0xFF;
             return advanceFixed(layout, p, limit, 32);
         }
-        if (wt == QwpConstants.TYPE_STRING || wt == QwpConstants.TYPE_VARCHAR
-                || wt == QwpConstants.TYPE_BINARY) {
-            // STRING/VARCHAR/BINARY all share the (N+1) x uint32 offsets + concatenated bytes layout.
+        if (wt == QwpConstants.TYPE_VARCHAR || wt == QwpConstants.TYPE_BINARY) {
+            // VARCHAR/BINARY share the (N+1) x uint32 offsets + concatenated bytes layout.
             // BINARY differs only in that the bytes are opaque (no UTF-8 contract).
             return parseStringColumn(layout, p, limit);
         }

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

@@ -461,10 +461,10 @@ private static int writeStringResultBatch(long buf, int nonNull, int totalBytes)
         p = putVarint(p, 1L);                         // column_count
         p = putByte(p, QwpConstants.SCHEMA_MODE_FULL);
         p = putVarint(p, 0L);                         // schema_id
-        // Schema entries (full): one column "s" of TYPE_STRING
+        // Schema entries (full): one column "s" of TYPE_VARCHAR
         p = putVarint(p, 1L);                         // column name length
         p = putByte(p, (byte) 's');
-        p = putByte(p, QwpConstants.TYPE_STRING);
+        p = putByte(p, QwpConstants.TYPE_VARCHAR);
         // Column body: null_flag = 0 (no nulls), offsets[nonNull+1] u32, then bytes.
         p = putByte(p, (byte) 0);                     // null_flag
         for (int i = 0; i < nonNull; i++) {

examples/src/main/java/com/example/query/TypedResultExample.java

@@ -84,7 +84,7 @@ private static void appendCell(StringBuilder out, QwpColumnBatch batch, int col,
             out.append(batch.getFloat(col, row));
         } else if (type == QwpConstants.TYPE_DOUBLE) {
             out.append(batch.getDouble(col, row));
-        } else if (type == QwpConstants.TYPE_STRING || type == QwpConstants.TYPE_SYMBOL) {
+        } else if (type == QwpConstants.TYPE_SYMBOL) {
             out.append(batch.getString(col, row));
         } else if (type == QwpConstants.TYPE_VARCHAR) {
             out.append(new String(batch.getVarchar(col, row)));