Add version() system information function.

This function is used by some PostgreSQL protocol based clients.

docs/appendices/release-notes/unreleased.rst

@@ -52,11 +52,11 @@ None
 Changes
 =======
 
+- Added the :ref:`version() <version>` system information function.
+
 - Added support for the PostgreSQL notation to refer to array types. For
   example, it is now possible to use ``text[]`` instead of ``array(test)``.
 
-None
-
 Fixes
 =====
 

docs/general/builtins/scalar.rst

@@ -2402,6 +2402,33 @@ Example:
     +--------------+
     SELECT 1 row in set (... sec)
 
+.. _version:
+
+``version``
+-----------
+
+Returns the CrateDB version information.
+
+Returns: ``text``
+
+Synopsis::
+
+  version()
+
+Example:
+
+::
+
+    cr> select version();
+    +---------...-+
+    | version()   |
+    +---------...-+
+    | CrateDB ... |
+    +---------...-+
+    SELECT 1 row in set (... sec)
+
+
+
 Special functions
 =================
 

sql/src/main/java/io/crate/expression/scalar/ScalarFunctionModule.java

@@ -63,6 +63,7 @@
 import io.crate.expression.scalar.systeminformation.CurrentSchemasFunction;
 import io.crate.expression.scalar.systeminformation.PgGetExpr;
 import io.crate.expression.scalar.systeminformation.PgTypeofFunction;
+import io.crate.expression.scalar.systeminformation.VersionFunction;
 import io.crate.expression.scalar.timestamp.CurrentTimestampFunction;
 import io.crate.expression.scalar.timestamp.TimezoneFunction;
 import io.crate.metadata.FunctionIdent;
@@ -171,6 +172,7 @@ protected void configure() {
         PgGetUserByIdFunction.register(this);
         PgTypeofFunction.register(this);
         register(new CurrentDatabaseFunction());
+        VersionFunction.register(this);
 
         // bind all registered functions and resolver
         // by doing it here instead of the register functions, plugins can also use the

sql/src/main/java/io/crate/expression/scalar/systeminformation/VersionFunction.java

@@ -0,0 +1,93 @@
+/*
+ * Licensed to Crate under one or more contributor license agreements.
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.  Crate 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.
+ *
+ * However, if you have executed another commercial license agreement
+ * with Crate these terms will supersede the license and you may use the
+ * software solely pursuant to the terms of the relevant commercial
+ * agreement.
+ */
+
+package io.crate.expression.scalar.systeminformation;
+
+import io.crate.data.Input;
+import io.crate.expression.scalar.ScalarFunctionModule;
+import io.crate.metadata.FunctionIdent;
+import io.crate.metadata.FunctionInfo;
+import io.crate.metadata.FunctionName;
+import io.crate.metadata.Scalar;
+import io.crate.metadata.TransactionContext;
+import io.crate.metadata.pgcatalog.PgCatalogSchemaInfo;
+import io.crate.types.DataTypes;
+import org.elasticsearch.Build;
+import org.elasticsearch.Version;
+
+import java.util.Collections;
+import java.util.Locale;
+
+public class VersionFunction extends Scalar<String, Void> {
+
+    public static final String NAME = "version";
+
+    private static final FunctionName FQN = new FunctionName(PgCatalogSchemaInfo.NAME, NAME);
+
+    protected static final FunctionInfo INFO = new FunctionInfo(
+        new FunctionIdent(FQN, Collections.emptyList()), DataTypes.DOUBLE,
+        FunctionInfo.Type.SCALAR, FunctionInfo.NO_FEATURES);
+
+    public static void register(ScalarFunctionModule scalarFunctionModule) {
+        scalarFunctionModule.register(new VersionFunction());
+    }
+
+    private static String formatVersion() {
+        String version = Version.displayVersion(Version.CURRENT, Version.CURRENT.isSnapshot());
+        String built = String.format(
+            Locale.ENGLISH,
+            "built %s/%s",
+            Build.CURRENT.hashShort(),
+            Build.CURRENT.timestamp());
+        String vmVersion = String.format(
+            Locale.ENGLISH,
+            "%s %s",
+            System.getProperty("java.vm.name"),
+            System.getProperty("java.vm.version"));
+        String osVersion = String.format(
+            Locale.ENGLISH,
+            "%s %s %s",
+            System.getProperty("os.name"),
+            System.getProperty("os.version"),
+            System.getProperty("os.arch"));
+
+        return String.format(
+            Locale.ENGLISH,
+            "CrateDB %s (%s, %s, %s)",
+            version,
+            built,
+            osVersion,
+            vmVersion);
+    }
+
+    private static final String VERSION = formatVersion();
+
+    @Override
+    public String evaluate(TransactionContext txnCtx, Input<Void>... args) {
+        return VERSION;
+    }
+
+    @Override
+    public FunctionInfo info() {
+        return INFO;
+    }
+}

sql/src/test/java/io/crate/expression/scalar/postgres/VersionFunctionTest.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to Crate under one or more contributor license agreements.
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.  Crate 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.
+ *
+ * However, if you have executed another commercial license agreement
+ * with Crate these terms will supersede the license and you may use the
+ * software solely pursuant to the terms of the relevant commercial
+ * agreement.
+ */
+
+package io.crate.expression.scalar.postgres;
+
+import io.crate.expression.scalar.AbstractScalarFunctionsTest;
+import org.elasticsearch.Version;
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.startsWith;
+
+public class VersionFunctionTest extends AbstractScalarFunctionsTest {
+
+    @Test
+    public void testVersion() {
+        String expected = "CrateDB " + Version.displayVersion(Version.CURRENT, Version.CURRENT.isSnapshot()) + " (";
+        assertEvaluate("version()", startsWith(expected));
+    }
+}