Queries optimizations:

- cache prepared statements and two-step queries
- skip reduce query if possible
 - do not use index snapshots by default

modules/core/src/main/java/org/apache/ignite/configuration/CacheConfiguration.java

@@ -373,6 +373,9 @@ public class CacheConfiguration<K, V> extends MutableConfiguration<K, V> {
     /** */
     private int sqlOnheapRowCacheSize = DFLT_SQL_ONHEAP_ROW_CACHE_SIZE;
 
+    /** */
+    private boolean snapshotableIdx;
+
     /** Copy on read flag. */
     private boolean cpOnRead = DFLT_COPY_ON_READ;
 
@@ -463,6 +466,7 @@ public CacheConfiguration(CompleteConfiguration<K, V> cfg) {
         rebalancePoolSize = cc.getRebalanceThreadPoolSize();
         rebalanceTimeout = cc.getRebalanceTimeout();
         rebalanceThrottle = cc.getRebalanceThrottle();
+        snapshotableIdx = cc.isSnapshotableIndex();
         sqlEscapeAll = cc.isSqlEscapeAll();
         sqlFuncCls = cc.getSqlFunctionClasses();
         sqlOnheapRowCacheSize = cc.getSqlOnheapRowCacheSize();
@@ -1899,6 +1903,32 @@ public CacheConfiguration<K, V> setSqlOnheapRowCacheSize(int size) {
         return this;
     }
 
+    /**
+     * Gets flag indicating whether SQL indexes should support snapshots.
+     *
+     * @return {@code True} if SQL indexes should support snapshots.
+     */
+    public boolean isSnapshotableIndex() {
+        return snapshotableIdx;
+    }
+
+    /**
+     * Sets flag indicating whether SQL indexes should support snapshots.
+     * <p>
+     * Default value is {@code false}.
+     * <p>
+     * <b>Note</b> that this flag is ignored if indexes are stored in offheap memory,
+     * for offheap indexes snapshots are always enabled.
+     *
+     * @param snapshotableIdx {@code True} if SQL indexes should support snapshots.
+     * @return {@code this} for chaining.
+     */
+    public CacheConfiguration<K, V> setSnapshotableIndex(boolean snapshotableIdx) {
+        this.snapshotableIdx = snapshotableIdx;
+
+        return this;
+    }
+
     /**
      * Gets array of cache plugin configurations.
      *

modules/core/src/main/java/org/apache/ignite/internal/processors/cache/query/GridCacheSqlQuery.java

@@ -52,6 +52,16 @@ public class GridCacheSqlQuery implements Message {
     /** */
     private byte[] paramsBytes;
 
+    /** */
+    @GridToStringInclude
+    @GridDirectTransient
+    private int[] paramIdxs;
+
+    /** */
+    @GridToStringInclude
+    @GridDirectTransient
+    private int paramsSize;
+
     /** */
     @GridToStringInclude
     @GridDirectTransient
@@ -77,6 +87,14 @@ public GridCacheSqlQuery(String qry, Object[] params) {
         this.qry = qry;
 
         this.params = F.isEmpty(params) ? EMPTY_PARAMS : params;
+        paramsSize = this.params.length;
+    }
+
+    /**
+     * @param paramIdxs Parameter indexes.
+     */
+    public void parameterIndexes(int[] paramIdxs) {
+        this.paramIdxs = paramIdxs;
     }
 
     /**
@@ -222,4 +240,28 @@ public void unmarshallParams(Marshaller m) throws IgniteCheckedException {
     @Override public byte fieldsCount() {
         return 3;
     }
+
+    /**
+     * @param args Arguments.
+     * @return Copy.
+     */
+    public GridCacheSqlQuery copy(Object[] args) {
+        GridCacheSqlQuery cp = new GridCacheSqlQuery();
+
+        cp.qry = qry;
+        cp.cols = cols;
+        cp.paramIdxs = paramIdxs;
+        cp.paramsSize = paramsSize;
+
+        if (F.isEmpty(args))
+            cp.params = EMPTY_PARAMS;
+        else {
+            cp.params = new Object[paramsSize];
+
+            for (int paramIdx : paramIdxs)
+                cp.params[paramIdx] = args[paramIdx];
+        }
+
+        return cp;
+    }
 }

modules/core/src/main/java/org/apache/ignite/internal/processors/cache/query/GridCacheTwoStepQuery.java

@@ -47,16 +47,27 @@ public class GridCacheTwoStepQuery {
     /** */
     private Set<String> spaces;
 
+    /** */
+    private final boolean skipMergeTbl;
+
     /**
      * @param spaces All spaces accessed in query.
      * @param rdc Reduce query.
+     * @param skipMergeTbl {@code True} if reduce query can skip merge table creation and
+     *      get data directly from merge index.
      */
-    public GridCacheTwoStepQuery(Set<String> spaces, GridCacheSqlQuery rdc) {
+    public GridCacheTwoStepQuery(Set<String> spaces, GridCacheSqlQuery rdc, boolean skipMergeTbl) {
         assert rdc != null;
 
         this.spaces = spaces;
-
         this.rdc = rdc;
+        this.skipMergeTbl = skipMergeTbl;
+    }
+    /**
+     * @return {@code True} if reduce query can skip merge table creation and get data directly from merge index.
+     */
+    public boolean skipMergeTable() {
+        return skipMergeTbl;
     }
 
     /**
@@ -89,9 +100,12 @@ public int pageSize() {
 
     /**
      * @param qry SQL Query.
+     * @return {@code this}.
      */
-    public void addMapQuery(GridCacheSqlQuery qry) {
+    public GridCacheTwoStepQuery addMapQuery(GridCacheSqlQuery qry) {
         mapQrys.add(qry);
+
+        return this;
     }
 
     /**
@@ -122,6 +136,21 @@ public void spaces(Set<String> spaces) {
         this.spaces = spaces;
     }
 
+    /**
+     * @param args New arguments to copy with.
+     * @return Copy.
+     */
+    public GridCacheTwoStepQuery copy(Object[] args) {
+        assert !explain;
+
+        GridCacheTwoStepQuery cp = new GridCacheTwoStepQuery(spaces, rdc.copy(args), skipMergeTbl);
+        cp.pageSize = pageSize;
+        for (int i = 0; i < mapQrys.size(); i++)
+            cp.mapQrys.add(mapQrys.get(i).copy(args));
+
+        return cp;
+    }
+
     /** {@inheritDoc} */
     @Override public String toString() {
         return S.toString(GridCacheTwoStepQuery.class, this);

modules/core/src/main/java/org/apache/ignite/internal/processors/query/GridQueryProcessor.java

@@ -1671,35 +1671,10 @@ public static void onCompleted(GridCacheContext<?, ?> cctx, Object res, Throwabl
                 ", duration=" + duration + ", fail=" + fail + ", res=" + res + ']');
     }
 
-    /**
-     *
-     */
-    private abstract static class Property {
-        /**
-         * Gets this property value from the given object.
-         *
-         * @param key Key.
-         * @param val Value.
-         * @return Property value.
-         * @throws IgniteCheckedException If failed.
-         */
-        public abstract Object value(Object key, Object val) throws IgniteCheckedException;
-
-        /**
-         * @return Property name.
-         */
-        public abstract String name();
-
-        /**
-         * @return Class member type.
-         */
-        public abstract Class<?> type();
-    }
-
     /**
      * Description of type property.
      */
-    private static class ClassProperty extends Property {
+    private static class ClassProperty extends GridQueryProperty {
         /** */
         private final Member member;
 
@@ -1794,7 +1769,7 @@ public boolean knowsClass(Class<?> cls) {
     /**
      *
      */
-    private class PortableProperty extends Property {
+    private class PortableProperty extends GridQueryProperty {
         /** Property name. */
         private String propName;
 
@@ -1938,7 +1913,7 @@ private static class TypeDescriptor implements GridQueryTypeDescriptor {
 
         /** */
         @GridToStringExclude
-        private final Map<String, Property> props = new HashMap<>();
+        private final Map<String, GridQueryProperty> props = new HashMap<>();
 
         /** */
         @GridToStringInclude
@@ -1992,12 +1967,17 @@ void name(String name) {
             return fields;
         }
 
+        /** {@inheritDoc} */
+        @Override public GridQueryProperty property(String name) {
+            return props.get(name);
+        }
+
         /** {@inheritDoc} */
         @SuppressWarnings("unchecked")
         @Override public <T> T value(String field, Object key, Object val) throws IgniteCheckedException {
             assert field != null;
 
-            Property prop = props.get(field);
+            GridQueryProperty prop = props.get(field);
 
             if (prop == null)
                 throw new IgniteCheckedException("Failed to find field '" + field + "' in type '" + name + "'.");
@@ -2096,7 +2076,7 @@ void keyClass(Class<?> keyCls) {
          * @param failOnDuplicate Fail on duplicate flag.
          * @throws IgniteCheckedException In case of error.
          */
-        public void addProperty(Property prop, boolean failOnDuplicate) throws IgniteCheckedException {
+        public void addProperty(GridQueryProperty prop, boolean failOnDuplicate) throws IgniteCheckedException {
             String name = prop.name();
 
             if (props.put(name, prop) != null && failOnDuplicate)

modules/core/src/main/java/org/apache/ignite/internal/processors/query/GridQueryProperty.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.ignite.internal.processors.query;
+
+import org.apache.ignite.IgniteCheckedException;
+
+/**
+ * Description and access method for query entity field.
+ */
+public abstract class GridQueryProperty {
+    /**
+     * Gets this property value from the given object.
+     *
+     * @param key Key.
+     * @param val Value.
+     * @return Property value.
+     * @throws IgniteCheckedException If failed.
+     */
+    public abstract Object value(Object key, Object val) throws IgniteCheckedException;
+
+    /**
+     * @return Property name.
+     */
+    public abstract String name();
+
+    /**
+     * @return Class member type.
+     */
+    public abstract Class<?> type();
+}

modules/core/src/main/java/org/apache/ignite/internal/processors/query/GridQueryTypeDescriptor.java

@@ -49,6 +49,12 @@ public interface GridQueryTypeDescriptor {
      */
     public <T> T value(String field, Object key, Object val) throws IgniteCheckedException;
 
+    /**
+     * @param name Property name.
+     * @return Property.
+     */
+    public GridQueryProperty property(String name);
+
     /**
      * Gets indexes for this type.
      *

modules/indexing/src/main/java/org/apache/ignite/internal/processors/query/h2/GridH2ResultSetIterator.java

@@ -40,15 +40,20 @@ public abstract class GridH2ResultSetIterator<T> extends GridCloseableIteratorAd
     /** */
     protected final Object[] row;
 
+    /** */
+    private final boolean closeStmt;
+
     /** */
     private boolean hasRow;
 
     /**
      * @param data Data array.
+     * @param closeStmt If {@code true} closes result set statement when iterator is closed.
      * @throws IgniteCheckedException If failed.
      */
-    protected GridH2ResultSetIterator(ResultSet data) throws IgniteCheckedException {
+    protected GridH2ResultSetIterator(ResultSet data, boolean closeStmt) throws IgniteCheckedException {
         this.data = data;
+        this.closeStmt = closeStmt;
 
         if (data != null) {
             try {
@@ -115,11 +120,13 @@ private boolean fetchNext() {
             // Nothing to close.
             return;
 
-        try {
-            U.closeQuiet(data.getStatement());
-        }
-        catch (SQLException e) {
-            throw new IgniteCheckedException(e);
+        if (closeStmt) {
+            try {
+                U.closeQuiet(data.getStatement());
+            }
+            catch (SQLException e) {
+                throw new IgniteCheckedException(e);
+            }
         }
 
         U.closeQuiet(data);