Fixes singletons and wip on HBase GroupBy

src/qir/ast/QIRNull.java

 package qir.ast;
 
-import com.oracle.truffle.api.source.SourceSection;
-
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 
@@ -9,20 +7,14 @@ import qir.util.QIRAny;
  * This class represents the {@code null} value, it is therefore a singleton.
  */
 public final class QIRNull extends QIRNode {
-    private QIRNull(final SourceSection source) {
-        super(source);
+    private QIRNull() {
+        super(null);
     }
 
-    private static final QIRNull singleton = new QIRNull(null);
-
     /**
-     * Use this method to refer to the {@code null} value.
-     *
-     * @return The unique representation of the {@code null} value.
+     * The unique representation of the {@code null} value.
      */
-    public static final QIRNull getInstance() {
-        return singleton;
-    }
+    public static final QIRNull instance = new QIRNull();
 
     @Override
     public final String toString() {
@@ -31,7 +23,7 @@ public final class QIRNull extends QIRNode {
 
     @Override
     public boolean equals(Object other) {
-        return other instanceof QIRNull || other instanceof QIRAny;
+        return other == instance || other == QIRAny.instance;
     }
 
     @Override

src/qir/ast/data/QIRLnil.java

 package qir.ast.data;
 
-import com.oracle.truffle.api.source.SourceSection;
-
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 
@@ -9,20 +7,14 @@ import qir.util.QIRAny;
  * This class represents the empty {@link QIRList}, it is therefore a singleton.
  */
 public final class QIRLnil extends QIRList {
-    private QIRLnil(final SourceSection source) {
-        super(source);
+    private QIRLnil() {
+        super(null);
     }
 
-    private static final QIRLnil singleton = new QIRLnil(null);
-
     /**
-     * Use this method to refer to the empty {@link QIRList}.
-     *
-     * @return The unique representation of the empty {@link QIRList}.
+     * The unique representation of the empty {@link QIRList}.
      */
-    public static final QIRLnil getInstance() {
-        return singleton;
-    }
+    public static final QIRLnil instance = new QIRLnil();
 
     @Override
     public final String toString() {
@@ -31,7 +23,7 @@ public final class QIRLnil extends QIRList {
 
     @Override
     public boolean equals(Object other) {
-        return other instanceof QIRLnil || other instanceof QIRAny;
+        return other == QIRLnil.instance || other == QIRAny.instance;
     }
 
     @Override

src/qir/ast/data/QIRTnil.java

 package qir.ast.data;
 
-import com.oracle.truffle.api.source.SourceSection;
-
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 
@@ -9,20 +7,14 @@ import qir.util.QIRAny;
  * This class represents the empty {@link QIRTuple}, it is therefore a singleton.
  */
 public final class QIRTnil extends QIRTuple {
-    private QIRTnil(final SourceSection source) {
-        super(source);
+    private QIRTnil() {
+        super(null);
     }
 
-    private static final QIRTnil singleton = new QIRTnil(null);
-
     /**
-     * Use this method to refer to the empty {@link QIRTuple}.
-     *
-     * @return The unique representation of the empty {@link QIRTuple}.
+     * The unique representation of the empty {@link QIRTuple}.
      */
-    public static final QIRTnil getInstance() {
-        return singleton;
-    }
+    public static final QIRTnil instance = new QIRTnil();
 
     @Override
     public final String toString() {
@@ -31,7 +23,7 @@ public final class QIRTnil extends QIRTuple {
 
     @Override
     public boolean equals(Object other) {
-        return other instanceof QIRTnil || other instanceof QIRAny;
+        return other == QIRTnil.instance || other == QIRAny.instance;
     }
 
     @Override

src/qir/ast/value/QIRBoolean.java

 package qir.ast.value;
 
-import com.oracle.truffle.api.source.SourceSection;
-
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 
@@ -9,17 +7,16 @@ import qir.util.QIRAny;
  * The {@link QIRBoolean} represents a boolean.
  */
 public final class QIRBoolean extends QIRBaseValue<Boolean> {
-    public QIRBoolean(final SourceSection source, final boolean value) {
-        super(source, value);
+    private QIRBoolean(final boolean value) {
+        super(null, value);
     }
 
+    public static final QIRBoolean qirTrue = new QIRBoolean(true);
+    public static final QIRBoolean qirFalse = new QIRBoolean(false);
+
     @Override
     public boolean equals(Object other) {
-        if (other instanceof QIRAny)
-            return true;
-        if (!(other instanceof QIRBoolean))
-            return false;
-        return value.equals(((QIRBoolean) other).value);
+        return this == other || other == QIRAny.instance;
     }
 
     @Override

src/qir/driver/QIREvaluationVisitor.java

@@ -24,7 +24,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode formatter = qirProject.formatter.accept(this);
         final QIRNode input = qirProject.child.accept(this);
         final Deque<QIRNode> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
+        QIRList result = QIRLnil.instance;
 
         if (input instanceof QIRLnil)
             return input;
@@ -39,7 +39,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
 
     @Override
     public final QIRNode visit(final QIRScan qirScan) {
-        throw new QIRException("Unreachable code reached.");
+        throw new QIRException("Cannot perform scan in QIR evaluation.");
     }
 
     @Override
@@ -47,7 +47,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode filter = qirFilter.filter.accept(this);
         final QIRNode input = qirFilter.child.accept(this);
         final Deque<QIRNode> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
+        QIRList result = QIRLnil.instance;
 
         if (input instanceof QIRLnil)
             return input;
@@ -55,9 +55,9 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
             return new QIRFilter(qirFilter.sourceSection, filter, input);
         for (QIRNode e = input; e instanceof QIRLcons; e = ((QIRLcons) e).tail) {
             final QIRNode pass = new QIRApply(null, filter, ((QIRLcons) e).value).accept(this);
-            if (pass.equals(new QIRBoolean(null, true)))
+            if (pass.equals(QIRBoolean.qirTrue))
                 tmp.push(((QIRLcons) e).value);
-            else if (!pass.equals(new QIRBoolean(null, false)))
+            else if (!pass.equals(QIRBoolean.qirFalse))
                 return new QIRFilter(qirFilter.sourceSection, pass, input);
         }
         while (!tmp.isEmpty())
@@ -81,7 +81,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode left = qirJoin.left.accept(this);
         final QIRNode right = qirJoin.right.accept(this);
         final Deque<QIRNode> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
+        QIRList result = QIRLnil.instance;
 
         if (left instanceof QIRLnil)
             return left;
@@ -90,9 +90,9 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         for (QIRNode l = left; l instanceof QIRLcons; l = ((QIRLcons) l).tail)
             for (QIRNode r = right; r instanceof QIRLcons; r = ((QIRLcons) r).tail) {
                 final QIRNode pass = new QIRApply(null, new QIRApply(null, filter, ((QIRLcons) l).value), ((QIRLcons) r).value).accept(this);
-                if (pass.equals(new QIRBoolean(null, true))) {
+                if (pass.equals(QIRBoolean.qirTrue)) {
                     final Deque<QIRTcons> s = new ArrayDeque<>();
-                    QIRNode res = QIRTnil.getInstance();
+                    QIRNode res = QIRTnil.instance;
                     for (QIRNode t = ((QIRLcons) l).value; t instanceof QIRTcons; t = ((QIRTcons) t).tail)
                         s.push((QIRTcons) t);
                     for (QIRNode t = ((QIRLcons) r).value; t instanceof QIRTcons; t = ((QIRTcons) t).tail)
@@ -100,7 +100,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
                     for (QIRTcons t : s)
                         res = new QIRTcons(t.sourceSection, t.id, t.value, res);
                     tmp.push(res);
-                } else if (!pass.equals(new QIRBoolean(null, false)))
+                } else if (!pass.equals(QIRBoolean.qirFalse))
                     return new QIRJoin(qirJoin.sourceSection, pass, left, right);
             }
         while (!tmp.isEmpty())
@@ -174,9 +174,9 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
     public final QIRNode visit(final QIRIf qirIf) {
         final QIRNode cond = qirIf.condition.accept(this);
 
-        if (cond.equals(new QIRBoolean(null, true)))
+        if (cond.equals(QIRBoolean.qirTrue))
             return qirIf.thenNode.accept(this);
-        if (cond.equals(new QIRBoolean(null, false)))
+        if (cond.equals(QIRBoolean.qirFalse))
             return qirIf.elseNode.accept(this);
         return new QIRIf(qirIf.sourceSection, cond, qirIf.thenNode, qirIf.elseNode);
     }
@@ -259,7 +259,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirAnd.right.accept(this);
 
         if (left instanceof QIRBoolean && right instanceof QIRBoolean)
-            return new QIRBoolean(qirAnd.sourceSection, ((QIRBoolean) left).value && ((QIRBoolean) right).value);
+            return ((QIRBoolean) left).value && ((QIRBoolean) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator && not defined for: " + left.getClass().getName() + " and " + right.getClass().getName() + ".");
         return new QIRAnd(qirAnd.sourceSection, left, right);
@@ -271,7 +271,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirOr.right.accept(this);
 
         if (left instanceof QIRBoolean && right instanceof QIRBoolean)
-            return new QIRBoolean(qirOr.sourceSection, ((QIRBoolean) left).value || ((QIRBoolean) right).value);
+            return ((QIRBoolean) left).value || ((QIRBoolean) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator || not defined for: " + left.getClass().getName() + " and " + right.getClass().getName() + ".");
         return new QIROr(qirOr.sourceSection, left, right);
@@ -283,13 +283,13 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirEqual.right.accept(this);
 
         if (left instanceof QIRNumber && right instanceof QIRNumber)
-            return new QIRBoolean(qirEqual.sourceSection, ((QIRNumber) left).value == ((QIRNumber) right).value);
+            return ((QIRNumber) left).value == ((QIRNumber) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRString && right instanceof QIRString)
-            return new QIRBoolean(qirEqual.sourceSection, ((QIRString) left).value.equals(((QIRString) right).value));
+            return ((QIRString) left).value.equals(((QIRString) right).value) ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBoolean && right instanceof QIRBoolean)
-            return new QIRBoolean(qirEqual.sourceSection, ((QIRBoolean) left).value == ((QIRBoolean) right).value);
+            return ((QIRBoolean) left).value == ((QIRBoolean) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBigNumber && right instanceof QIRBigNumber)
-            return new QIRBoolean(qirEqual.sourceSection, ((QIRBigNumber) left).value.equals(((QIRBigNumber) right).value));
+            return ((QIRBigNumber) left).value.equals(((QIRBigNumber) right).value) ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator == not defined for: " + left.getClass().getName() + " and " + right.getClass().getName() + ".");
         return new QIREqual(qirEqual.sourceSection, left, right);
@@ -301,11 +301,11 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirLowerOrEqual.right.accept(this);
 
         if (left instanceof QIRNumber && right instanceof QIRNumber)
-            return new QIRBoolean(qirLowerOrEqual.sourceSection, ((QIRNumber) left).value <= ((QIRNumber) right).value);
+            return ((QIRNumber) left).value <= ((QIRNumber) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRString && right instanceof QIRString)
-            return new QIRBoolean(qirLowerOrEqual.sourceSection, ((QIRString) left).value.compareTo(((QIRString) right).value) <= 0);
+            return ((QIRString) left).value.compareTo(((QIRString) right).value) <= 0 ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBigNumber && right instanceof QIRBigNumber)
-            return new QIRBoolean(qirLowerOrEqual.sourceSection, ((QIRBigNumber) left).value.compareTo(((QIRBigNumber) right).value) <= 0);
+            return ((QIRBigNumber) left).value.compareTo(((QIRBigNumber) right).value) <= 0 ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator <= not defined for: " + left.getClass().getName() + " and " + right.getClass().getName() + ".");
         return new QIRLowerOrEqual(qirLowerOrEqual.sourceSection, left, right);
@@ -317,11 +317,11 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirLowerThan.right.accept(this);
 
         if (left instanceof QIRNumber && right instanceof QIRNumber)
-            return new QIRBoolean(qirLowerThan.sourceSection, ((QIRNumber) left).value < ((QIRNumber) right).value);
+            return ((QIRNumber) left).value < ((QIRNumber) right).value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRString && right instanceof QIRString)
-            return new QIRBoolean(qirLowerThan.sourceSection, ((QIRString) left).value.compareTo(((QIRString) right).value) < 0);
+            return ((QIRString) left).value.compareTo(((QIRString) right).value) < 0 ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBigNumber && right instanceof QIRBigNumber)
-            return new QIRBoolean(qirLowerThan.sourceSection, ((QIRBigNumber) left).value.compareTo(((QIRBigNumber) right).value) < 0);
+            return ((QIRBigNumber) left).value.compareTo(((QIRBigNumber) right).value) < 0 ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator < not defined for: " + left.getClass().getName() + " and " + right.getClass().getName() + ".");
         return new QIRLowerThan(qirLowerThan.sourceSection, left, right);
@@ -332,7 +332,7 @@ final class QIREvaluationVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode expr = qirNot.child.accept(this);
 
         if (expr instanceof QIRBoolean)
-            return new QIRBoolean(qirNot.sourceSection, !((QIRBoolean) expr).value);
+            return ((QIRBoolean) expr).value ? QIRBoolean.qirFalse : QIRBoolean.qirTrue;
         if (expr instanceof QIRBaseValue<?>)
             throw new QIRException("Typing error: binary operator ! not defined for: " + expr.getClass().getName() + ".");
         return new QIRNot(qirNot.sourceSection, expr);

src/qir/driver/QIRGreedyReduceVisitor.java

@@ -104,9 +104,9 @@ final class QIRGreedyReduceVisitor implements IQIRVisitor<QIRNode> {
     public final QIRNode visit(final QIRIf qirIf) {
         final QIRNode cond = qirIf.condition.accept(this);
 
-        if (cond.equals(new QIRBoolean(null, true)))
+        if (cond.equals(QIRBoolean.qirTrue))
             return qirIf.thenNode.accept(this);
-        if (cond.equals(new QIRBoolean(null, false)))
+        if (cond.equals(QIRBoolean.qirFalse))
             return qirIf.elseNode.accept(this);
         return new QIRIf(qirIf.sourceSection, cond, qirIf.thenNode.accept(this), qirIf.elseNode.accept(this));
     }
@@ -152,9 +152,9 @@ final class QIRGreedyReduceVisitor implements IQIRVisitor<QIRNode> {
         final QIRNode right = qirEqual.right.accept(this);
 
         if (left.equals(right))
-            return new QIRBoolean(null, true);
+            return QIRBoolean.qirTrue;
         if (left instanceof QIRBaseValue<?> && right instanceof QIRBaseValue<?>)
-            return new QIRBoolean(null, false);
+            return QIRBoolean.qirFalse;
         return new QIREqual(qirEqual.sourceSection, left, right);
     }
 

src/qir/driver/hbase/HBaseDriver.java

@@ -35,6 +35,7 @@ import qir.util.QIRException;
  */
 public final class HBaseDriver extends DBDriver<HBaseQuery, String> {
     protected Connection conn;
+    private Configuration conf;
 
     public HBaseDriver(final String configFile) {
         super(configFile);
@@ -44,8 +45,8 @@ public final class HBaseDriver extends DBDriver<HBaseQuery, String> {
     public void openConnection(final String configFile) throws QIRException {
         if (conn != null)
             closeConnection();
-        final Configuration conf = HBaseConfiguration.create();
 
+        conf = HBaseConfiguration.create();
         conf.addResource(configFile);
         try {
             conn = ConnectionFactory.createConnection(conf);
@@ -76,20 +77,20 @@ public final class HBaseDriver extends DBDriver<HBaseQuery, String> {
 
     @Override
     public HBaseQuery translate(final QIRNode root) {
-        return root.accept(new QIRHBaseQueryVisitor());
+        return root.accept(new QIRHBaseQueryVisitor(conf));
     }
 
     @Override
     public QIRList run(final HBaseQuery query) throws QIRException {
         final ResultScanner rs;
         final Deque<QIRTuple> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
+        QIRList result = QIRLnil.instance;
         QIRNode data;
 
         try (final Table table = conn.getTable(TableName.valueOf(query.tableName))) {
             rs = table.getScanner(query.scan);
             for (Result r = rs.next(); r != null; r = rs.next()) {
-                QIRTuple newTuple = QIRTnil.getInstance();
+                QIRTuple newTuple = QIRTnil.instance;
                 for (final Cell cell : r.listCells()) {
                     final String value = Bytes.toString(CellUtil.cloneValue(cell));
                     try {

src/qir/driver/hbase/QIRHBaseQueryVisitor.java

 package qir.driver.hbase;
 
+import java.io.IOException;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.client.Scan;
+import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
+import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
+import org.apache.hadoop.hbase.mapreduce.TableMapper;
+import org.apache.hadoop.hbase.mapreduce.TableReducer;
+import org.apache.hadoop.mapreduce.Job;
 
 import qir.ast.*;
 import qir.ast.data.*;
@@ -13,10 +22,16 @@ import qir.util.QIRException;
  * Translation from a QIR query to a HBase query in {@link HBaseQuery} format.
  */
 final class QIRHBaseQueryVisitor implements IQIRVisitor<HBaseQuery> {
+    final Configuration conf;
+
+    QIRHBaseQueryVisitor(final Configuration conf) {
+        this.conf = conf;
+    }
+
     @Override
     public final HBaseQuery visit(QIRProject qirProject) {
         if (!(qirProject.formatter instanceof QIRLambda && ((QIRLambda) qirProject.formatter).body instanceof QIRTcons))
-            throw new QIRException("QIR SQL Project not implemented for formatter type: " + qirProject.formatter.getClass());
+            throw new QIRException("QIR HBase Project not implemented for formatter type: " + qirProject.formatter.getClass());
         final HBaseQuery child = qirProject.child.accept(this);
 
         for (QIRNode formatter = ((QIRLambda) qirProject.formatter).body; formatter instanceof QIRTcons; formatter = ((QIRTcons) formatter).tail)
@@ -39,6 +54,37 @@ final class QIRHBaseQueryVisitor implements IQIRVisitor<HBaseQuery> {
         return child;
     }
 
+    private static class GroupByMapper extends TableMapper<String, String> {
+        @Override
+        public void map(ImmutableBytesWritable row, Result value, Context context) throws InterruptedException, IOException {
+        }
+    }
+
+    private static class GroupByReducer extends TableReducer<ImmutableBytesWritable, String, ImmutableBytesWritable> {
+        @Override
+        public void reduce(ImmutableBytesWritable key, Iterable<String> values, Context context) {
+        }
+    }
+
+    @Override
+    public final HBaseQuery visit(QIRGroupBy qirGroup) {
+        if (!(qirGroup.group instanceof QIRLambda))
+            throw new QIRException("QIR HBase Group not implemented for group type: " + qirGroup.group.getClass());
+        if (!(qirGroup.child instanceof QIRProject))
+            throw new QIRException("Invalid QIR HBase Group");
+        final HBaseQuery child = qirGroup.child.accept(this);
+        final Job job;
+        try {
+            job = Job.getInstance(conf);
+            job.setJarByClass(QIRHBaseQueryVisitor.class);
+            TableMapReduceUtil.initTableMapperJob(child.tableName, child.scan, GroupByMapper.class, String.class, String.class, job);
+            TableMapReduceUtil.initTableReducerJob(child.tableName, GroupByReducer.class, job);
+        } catch (IOException e) {
+            throw new QIRException(e.getMessage());
+        }
+        return child;
+    }
+
     @Override
     public final <DBRepr, ConnData> HBaseQuery visit(final QIRDBNode<DBRepr, ConnData> qirDBNode) {
         return (HBaseQuery) qirDBNode.translation;

src/qir/driver/sql/QIRSQLStringVisitor.java

@@ -73,10 +73,10 @@ final class QIRSQLStringVisitor implements IQIRVisitor<String> {
                         ((QIRLambda) qirOrder.isAscending).body instanceof QIRLcons) {
             QIRNode rows = ((QIRLambda) qirOrder.order).body;
             QIRNode ascs = ((QIRLambda) qirOrder.isAscending).body;
-            String o = ((QIRLcons) rows).value.accept(this) + (((QIRLcons) ascs).value.accept(this).equals(new QIRBoolean(null, true)) ? "" : " desc");
+            String o = ((QIRLcons) rows).value.accept(this) + (((QIRLcons) ascs).value.accept(this).equals(QIRBoolean.qirTrue) ? "" : " desc");
 
             for (rows = ((QIRLcons) rows).tail, ascs = ((QIRLcons) ascs).tail; rows instanceof QIRLcons; rows = ((QIRLcons) rows).tail, ascs = ((QIRLcons) ascs).tail)
-                o += ", " + ((QIRLcons) rows).value.accept(this) + (((QIRLcons) ascs).value.accept(this).equals(new QIRBoolean(null, true)) ? "" : " desc");
+                o += ", " + ((QIRLcons) rows).value.accept(this) + (((QIRLcons) ascs).value.accept(this).equals(QIRBoolean.qirTrue) ? "" : " desc");
             return "select * from (" + qirOrder.child.accept(this) + ") as " + ((QIRLambda) qirOrder.order).var.accept(this) + " order by " + o;
         }
         throw new QIRException("QIR SQL OrderBy not implemented for: " + qirOrder.order.getClass() + " and " + qirOrder.isAscending.getClass());
@@ -269,7 +269,7 @@ final class QIRSQLStringVisitor implements IQIRVisitor<String> {
 
     @Override
     public final String visit(final QIRLdestr qirLdestr) {
-        final QIRAny any = QIRAny.getInstance();
+        final QIRAny any = QIRAny.instance;
         if (qirLdestr.equals(new QIRLdestr(null, any, any,
                         new QIRLambda(null, null, new QIRVariable(null, "head", null), new QIRLambda(null, null, new QIRVariable(null, "tail", null), new QIRVariable(null, "tail", null))))))
             return "select * from (" + qirLdestr.list.accept(this) + ") as " + genFreshId() + " limit 1";

src/qir/driver/sql/SQLStringDriver.java

@@ -47,11 +47,11 @@ public abstract class SQLStringDriver extends SQLDriver<String> {
             final Statement stmt = conn.createStatement();
             final ResultSet rs = stmt.executeQuery(query);
             final Deque<QIRTuple> tmp = new ArrayDeque<>();
-            QIRList result = QIRLnil.getInstance();
+            QIRList result = QIRLnil.instance;
             QIRNode data;
 
             while (rs.next()) {
-                QIRTuple newTuple = QIRTnil.getInstance();
+                QIRTuple newTuple = QIRTnil.instance;
                 for (int i = rs.getMetaData().getColumnCount(); i >= 1; i--) {
                     int type = rs.getMetaData().getColumnType(i);
                     switch (type) {
@@ -61,13 +61,13 @@ public abstract class SQLStringDriver extends SQLDriver<String> {
                             data = new QIRNumber(null, rs.getLong(i));
                             break;
                         case Types.BOOLEAN:
-                            data = new QIRBoolean(null, rs.getBoolean(i));
+                            data = rs.getBoolean(i) ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
                             break;
                         case Types.DOUBLE:
                             data = new QIRDouble(null, rs.getDouble(i));
                             break;
                         case Types.NULL:
-                            data = QIRNull.getInstance();
+                            data = QIRNull.instance;
                             break;
                         case Types.OTHER:
                             String v = rs.getString(i);
@@ -81,7 +81,7 @@ public abstract class SQLStringDriver extends SQLDriver<String> {
                                 if (value instanceof Long)
                                     data = new QIRNumber(null, (Long) value);
                                 else if (value instanceof Boolean)
-                                    data = new QIRBoolean(null, (Boolean) value);
+                                    data = (Boolean) value ? QIRBoolean.qirTrue : QIRBoolean.qirFalse;
                                 else
                                     data = new QIRString(null, value.toString());
                             } catch (IOException | ClassNotFoundException e) {

src/qir/util/QIRAny.java

 package qir.util;
 
-import com.oracle.truffle.api.source.SourceSection;
-
 import qir.ast.QIRNode;
 import qir.driver.IQIRVisitor;
 
@@ -9,23 +7,14 @@ import qir.driver.IQIRVisitor;
  * This class represents any QIRNode.
  */
 public final class QIRAny extends QIRNode {
-    private QIRAny(final SourceSection src) {
-        super(src);
+    private QIRAny() {
+        super(null);
     }
 
     /**
      * The only instance of {@link QIRAny}.
      */
-    private static final QIRAny singleton = new QIRAny(null);
-
-    /**
-     * Use this method to refer to any QIRNode.
-     *
-     * @return The unique representation of QIRAny.
-     */
-    public static final QIRAny getInstance() {
-        return singleton;
-    }
+    public static final QIRAny instance = new QIRAny();
 
     @Override
     public final String toString() {
@@ -34,7 +23,7 @@ public final class QIRAny extends QIRNode {
 
     @Override
     public boolean equals(Object other) {
-        return other instanceof QIRAny;
+        return other instanceof QIRNode;
     }
 
     @Override