#6 replaced arrays with explicit variables for clarity and performance.

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/AbstractAggregatorFunction.java

-/*
- * Copyright (c) 2014. Vlad Ilyushchenko
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.nfsdb.lang.cst.impl.agg;
-
-import com.nfsdb.factory.configuration.ColumnMetadata;
-
-public abstract class AbstractAggregatorFunction implements AggregatorFunction {
-
-    private int map[];
-
-    @Override
-    public final ColumnMetadata[] getColumns() {
-        ColumnMetadata[] m = getColumnsInternal();
-        map = new int[m.length];
-        return m;
-    }
-
-    @Override
-    public final void mapColumn(int k, int i) {
-        map[k] = i;
-    }
-
-    protected abstract ColumnMetadata[] getColumnsInternal();
-
-    protected int map(int x) {
-        return map[x];
-    }
-}

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/AbstractSingleColumnAggregatorFunction.java

 /*
- * Copyright (c) 2014. Vlad Ilyushchenko
+ * Copyright (c) 2014-2015. Vlad Ilyushchenko
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,25 +20,27 @@ import com.nfsdb.factory.configuration.ColumnMetadata;
 import com.nfsdb.lang.cst.impl.qry.Record;
 import com.nfsdb.lang.cst.impl.qry.RecordSource;
 
-public abstract class AbstractSingleColumnAggregatorFunction extends AbstractAggregatorFunction {
+public abstract class AbstractSingleColumnAggregatorFunction implements AggregatorFunction {
     private final ColumnMetadata[] meta = new ColumnMetadata[1];
-    private int columnIndex;
+    protected int recordIndex;
+    protected int valueIndex;
 
     public AbstractSingleColumnAggregatorFunction(ColumnMetadata meta) {
         this.meta[0] = meta;
     }
 
     @Override
-    protected final ColumnMetadata[] getColumnsInternal() {
+    public ColumnMetadata[] getColumns() {
         return meta;
     }
 
-    protected final int getColumnIndex() {
-        return columnIndex;
+    @Override
+    public void mapColumn(int k, int i) {
+        valueIndex = i;
     }
 
     @Override
-    public final void prepareSource(RecordSource<? extends Record> source) {
-        this.columnIndex = source.getMetadata().getColumnIndex(meta[0].name);
+    public void prepareSource(RecordSource<? extends Record> source) {
+        this.recordIndex = source.getMetadata().getColumnIndex(meta[0].name);
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/CountIntAggregatorFunction.java

@@ -22,30 +22,24 @@ import com.nfsdb.factory.configuration.ColumnMetadata;
 import com.nfsdb.lang.cst.impl.qry.Record;
 import com.nfsdb.lang.cst.impl.qry.RecordSource;
 
-public class CountIntAggregatorFunction extends AbstractAggregatorFunction {
+public class CountIntAggregatorFunction extends AbstractSingleColumnAggregatorFunction {
 
-    private final ColumnMetadata[] meta = new ColumnMetadata[1];
 
     public CountIntAggregatorFunction(String name) {
-        this.meta[0] = new ColumnMetadata().setName(name).setType(ColumnType.INT);
-    }
-
-    @Override
-    protected ColumnMetadata[] getColumnsInternal() {
-        return meta;
+        super(new ColumnMetadata().setName(name).setType(ColumnType.INT));
     }
 
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putInt(map(0), 1);
+            values.putInt(valueIndex, 1);
         } else {
-            values.putInt(map(0), values.getInt(map(0)) + 1);
+            values.putInt(valueIndex, values.getInt(valueIndex) + 1);
         }
     }
 
     @Override
     public void prepareSource(RecordSource<? extends Record> source) {
-
+        // do not call parent method, which will be trying to lookup column in record source.
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/CountLongAggregatorFunction.java

@@ -22,32 +22,23 @@ import com.nfsdb.factory.configuration.ColumnMetadata;
 import com.nfsdb.lang.cst.impl.qry.Record;
 import com.nfsdb.lang.cst.impl.qry.RecordSource;
 
-public class CountLongAggregatorFunction extends AbstractAggregatorFunction {
-
-    private final ColumnMetadata[] meta = new ColumnMetadata[1];
+public class CountLongAggregatorFunction extends AbstractSingleColumnAggregatorFunction {
 
     public CountLongAggregatorFunction(String name) {
-        this.meta[0] = new ColumnMetadata();
-        this.meta[0].name = name;
-        this.meta[0].type = ColumnType.LONG;
-    }
-
-    @Override
-    protected ColumnMetadata[] getColumnsInternal() {
-        return meta;
+        super(new ColumnMetadata().setName(name).setType(ColumnType.LONG));
     }
 
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putLong(map(0), 1);
+            values.putLong(valueIndex, 1);
         } else {
-            values.putLong(map(0), values.getLong(map(0)) + 1);
+            values.putLong(valueIndex, values.getLong(valueIndex) + 1);
         }
     }
 
     @Override
     public void prepareSource(RecordSource<? extends Record> source) {
-
+        // do not call parent method, which will be trying to lookup column in record source.
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/FirstDoubleAggregationFunction.java

 /*
- * Copyright (c) 2014. Vlad Ilyushchenko
+ * Copyright (c) 2014-2015. Vlad Ilyushchenko
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,7 +29,7 @@ public class FirstDoubleAggregationFunction extends AbstractSingleColumnAggregat
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putDouble(map(0), rec.getDouble(getColumnIndex()));
+            values.putDouble(valueIndex, rec.getDouble(recordIndex));
         }
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/FirstLongAggregationFunction.java

@@ -29,7 +29,7 @@ public class FirstLongAggregationFunction extends AbstractSingleColumnAggregator
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putLong(map(0), rec.getLong(getColumnIndex()));
+            values.putLong(valueIndex, rec.getLong(recordIndex));
         }
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/LastDoubleAggregationFunction.java

 /*
- * Copyright (c) 2014. Vlad Ilyushchenko
+ * Copyright (c) 2014-2015. Vlad Ilyushchenko
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,6 @@ public class LastDoubleAggregationFunction extends AbstractSingleColumnAggregato
 
     @Override
     public void calculate(Record rec, MapValues values) {
-        values.putDouble(map(0), rec.getDouble(getColumnIndex()));
+        values.putDouble(valueIndex, rec.getDouble(recordIndex));
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/LastLongAggregationFunction.java

@@ -28,6 +28,6 @@ public class LastLongAggregationFunction extends AbstractSingleColumnAggregatorF
 
     @Override
     public void calculate(Record rec, MapValues values) {
-        values.putLong(map(0), rec.getLong(getColumnIndex()));
+        values.putLong(valueIndex, rec.getLong(recordIndex));
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/SumDoubleAggregationFunction.java

@@ -28,10 +28,9 @@ public class SumDoubleAggregationFunction extends AbstractSingleColumnAggregator
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putDouble(map(0), rec.getDouble(getColumnIndex()));
+            values.putDouble(valueIndex, rec.getDouble(recordIndex));
         } else {
-            int c = map(0);
-            values.putDouble(c, values.getDouble(c) + rec.getDouble(getColumnIndex()));
+            values.putDouble(valueIndex, values.getDouble(valueIndex) + rec.getDouble(recordIndex));
         }
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/SumIntAggregationFunction.java

@@ -28,10 +28,9 @@ public class SumIntAggregationFunction extends AbstractSingleColumnAggregatorFun
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putInt(map(0), rec.getInt(getColumnIndex()));
+            values.putInt(valueIndex, rec.getInt(recordIndex));
         } else {
-            int c = map(0);
-            values.putInt(c, values.getInt(c) + rec.getInt(getColumnIndex()));
+            values.putInt(valueIndex, values.getInt(valueIndex) + rec.getInt(recordIndex));
         }
     }
 }

nfsdb-core/src/main/java/com/nfsdb/lang/cst/impl/agg/SumIntToLongAggregationFunction.java

@@ -29,10 +29,9 @@ public class SumIntToLongAggregationFunction extends AbstractSingleColumnAggrega
     @Override
     public void calculate(Record rec, MapValues values) {
         if (values.isNew()) {
-            values.putLong(map(0), rec.getInt(getColumnIndex()));
+            values.putLong(valueIndex, rec.getInt(recordIndex));
         } else {
-            int c = map(0);
-            values.putLong(c, values.getLong(c) + rec.getInt(getColumnIndex()));
+            values.putLong(valueIndex, values.getLong(valueIndex) + rec.getInt(recordIndex));
         }
     }
 }