Make wait() method wait for query execution

With Impala the `\ThriftSQL\ImpalaQuery` object is ready as soon as the query is parsed / accepted to match up with `wait()` method with Hive fetch up to the first 2 rows during the `wait()` method so that the query gets executed.

Author: xyu

ThriftSQL.phar

@@ -15,6 +15,10 @@ public function __construct( $response, $client ) {
   }
 
   public function wait() {
+    if ( $this->_ready ) {
+      return $this;
+    }
+
     // Wait for results
     $sleeper = new \ThriftSQL\Utils\Sleeper();
     $sleeper->reset();

src/ThriftSQL/HiveQuery.php

@@ -7,6 +7,7 @@ class ImpalaQuery implements \ThriftSQLQuery {
   private $_handle;
   private $_client;
   private $_ready;
+  private $_lastResponse;
 
   public function __construct( $queryStr, $client ) {
     $queryCleaner = new \ThriftSQL\Utils\QueryCleaner();
@@ -19,14 +20,15 @@ public function __construct( $queryStr, $client ) {
   }
 
   public function wait() {
-    $sleeper = new \ThriftSQL\Utils\Sleeper();
+    if ( $this->_ready ) {
+      return $this;
+    }
 
-    // Wait for results
+    // Wait for query to be ready
+    $sleeper = new \ThriftSQL\Utils\Sleeper();
     $sleeper->reset();
     do {
-
       $slept = $sleeper->sleep()->getSleptSecs();
-
       if ( $slept > 18000 ) { // 5 Hours
         // TODO: Actually kill the query then throw exception.
         throw new \ThriftSQL\Exception( 'Impala Query Killed!' );
@@ -51,35 +53,47 @@ public function wait() {
 
     } while (true);
 
+    // Wait for results by fetching some rows -- triggers query to run
+    $this->_fetchResponse( 2 );
+
     $this->_ready = true;
     return $this;
   }
 
   public function fetch( $maxRows ) {
+    $result = array();
     if ( !$this->_ready ) {
       throw new \ThriftSQL\Exception( "Query is not ready. Call `->wait()` before `->fetch()`" );
     }
     try {
-      $sleeper = new \ThriftSQL\Utils\Sleeper();
-      $sleeper->reset();
-
-      do {
-        $response = $this->_client->fetch( $this->_handle, false, $maxRows );
-        if ( $response->ready ) {
-          break;
-        }
-        $slept = $sleeper->sleep()->getSleptSecs();
-
-        if ( $slept > 60 ) { // 1 minute
-          throw new \ThriftSQL\Exception( 'Impala Query took too long to fetch!' );
-        }
-
-      } while ( true );
+      if ( !( $this->_lastResponse instanceof \ThriftSQL\Results ) ) {
+        $this->_fetchResponse( $maxRows );
+      }
 
-      return $this->_parseResponse( $response );
+      $result = $this->_parseResponse( $this->_lastResponse );
+      $this->_lastResponse = null;
     } catch( Exception $e ) {
       throw new \ThriftSQL\Exception( $e->getMessage() );
     }
+
+    return $result;
+  }
+
+  private function _fetchResponse( $maxRows ) {
+    $sleeper = new \ThriftSQL\Utils\Sleeper();
+    $sleeper->reset();
+
+    do {
+      $this->_lastResponse = $this->_client->fetch( $this->_handle, false, $maxRows );
+      if ( $this->_lastResponse->ready ) {
+        return;
+      }
+
+      if ( $sleeper->sleep()->getSleptSecs() > 60 ) { // 1 minute
+        throw new \ThriftSQL\Exception( 'Impala Query took too long to fetch!' );
+      }
+
+    } while ( true );
   }
 
   private function _parseResponse( $response ) {