From cb391a1856cb8c79694cd5a4485c173efb557522 Mon Sep 17 00:00:00 2001
From: Dries Buytaert <dries@buytaert.net>
Date: Sun, 4 Apr 2010 07:20:05 +0000
Subject: - Patch #748340 by Berdir, andypost, catch, noahb, Crell:
 MySQL-optimized tableExists() implementation.

---
 includes/database/mysql/schema.inc | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

(limited to 'includes/database/mysql')

diff --git a/includes/database/mysql/schema.inc b/includes/database/mysql/schema.inc
index 9af75fd50..93c547eea 100644
--- a/includes/database/mysql/schema.inc
+++ b/includes/database/mysql/schema.inc
@@ -460,6 +460,40 @@ class DatabaseSchema_mysql extends DatabaseSchema {
     return preg_replace('/; InnoDB free:.*$/', '', $comment);
   }
 
+  public function tableExists($table) {
+    // The information_schema table is very slow to query under MySQL 5.0.
+    // Instead, we try to select from the table in question.  If it fails,
+    // the most likely reason is that it does not exist. That is dramatically
+    // faster than using information_schema.
+    // @link http://bugs.mysql.com/bug.php?id=19588
+    // @todo: This override should be removed once we require a version of MySQL
+    // that has that bug fixed.
+    try {
+      $this->connection->queryRange("SELECT 1 FROM {" . $table . "}", 0, 1);
+      return TRUE;
+    }
+    catch (Exception $e) {
+      return FALSE;
+    }
+  }
+
+  public function fieldExists($table, $column) {
+    // The information_schema table is very slow to query under MySQL 5.0.
+    // Instead, we try to select from the table and field in question. If it
+    // fails, the most likely reason is that it does not exist. That is
+    // dramatically faster than using information_schema.
+    // @link http://bugs.mysql.com/bug.php?id=19588
+    // @todo: This override should be removed once we require a version of MySQL
+    // that has that bug fixed.
+    try {
+      $this->connection->queryRange("SELECT $column FROM {" . $table . "}", 0, 1);
+      return TRUE;
+    }
+    catch (Exception $e) {
+      return FALSE;
+    }
+  }
+
 }
 
 /**
-- 
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