From 15aa8a612a6d4660c2aa71f9ea0d66593e277125 Mon Sep 17 00:00:00 2001
From: marcus <marcus@36083f99-b078-4883-b0ff-0f9b5a30f544>
Date: Mon, 3 Nov 2008 17:24:16 +0000
Subject: Experimental database query caching, please report problems asap.

git-svn-id: https://code.elgg.org/elgg/trunk@2381 36083f99-b078-4883-b0ff-0f9b5a30f544
---
 engine/lib/database.php | 79 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 56 insertions(+), 23 deletions(-)

diff --git a/engine/lib/database.php b/engine/lib/database.php
index e1f007399..640b1aa5b 100644
--- a/engine/lib/database.php
+++ b/engine/lib/database.php
@@ -13,6 +13,7 @@
 	 */
 
 	$DB_PROFILE = array();
+	//$DB_QUERY_CACHE = array();
 	
 	/**
 	 * Connect to the database server and use the Elgg database for a particular database link
@@ -151,20 +152,23 @@
     
         function get_data($query, $callback = "") {
             
-            global $CONFIG, $dbcalls, $DB_PROFILE;
+            global $CONFIG, $dbcalls, $DB_PROFILE, $DB_QUERY_CACHE;
             
             $dblink = get_db_link('read');
             
             $resultarray = array();
+            
+            if (!$DB_QUERY_CACHE) $DB_QUERY_CACHE = array();
+       		if (isset($DB_QUERY_CACHE[$query])) {
+       			if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            		error_log ("$query results returned from cache");
+            	//return $DB_QUERY_CACHE[$query];
+            }
+            
             $dbcalls++;
             
         	if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
-            {
             	$DB_PROFILE[] = $query;
-            	
-            	//error_log("--- DB QUERY --- $query");
-            	//error_log("--- EXPLANATION --- " . print_r(explain_query($query,$dblink), true));
-            }
             
             if ($result = mysql_query("$query", $dblink)) {
                 while ($row = mysql_fetch_object($result)) {
@@ -183,7 +187,13 @@
        				error_log("WARNING: DB query \"$query\" returned no results.");
        				
                 return false;
-            }
+            }
+            
+            // Cache result
+            if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            	error_log("$query results cached");
+            $DB_QUERY_CACHE[$query] = $resultarray;
+            
             return $resultarray;
         }
         
@@ -195,24 +205,32 @@
     
         function get_data_row($query) {
             
-            global $CONFIG, $dbcalls, $DB_PROFILE;
+            global $CONFIG, $dbcalls, $DB_PROFILE, $DB_QUERY_CACHE;
             
             $dblink = get_db_link('read');
-            
+            
+            if (!$DB_QUERY_CACHE) $DB_QUERY_CACHE = array();
+        	if (isset($DB_QUERY_CACHE[$query])) {
+        		if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            		error_log ("$query results returned from cache");
+            	//return $DB_QUERY_CACHE[$query];
+            }
+            
             $dbcalls++;
             
         	if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
-            {
             	$DB_PROFILE[] = $query;
-            	
-            	//error_log("--- DB QUERY --- $query");
-            	//error_log("--- EXPLANATION --- " . print_r(explain_query($query,$dblink), true));
-            }
             
-            if ($result = mysql_query("$query", $dblink)) {
-                while ($row = mysql_fetch_object($result)) {
-                    return $row;
-                }
+            if ($result = mysql_query("$query", $dblink)) {
+            	
+            	$row = mysql_fetch_object($result);
+            	
+            	// Cache result (even if query returned no data
+            	if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+                	error_log("$query results cached");
+            	$DB_QUERY_CACHE[$query] = $row;
+            	
+                if ($row) return $row;
             }
             
             if (mysql_errno($dblink))
@@ -233,7 +251,7 @@
     
         function insert_data($query) {
             
-            global $CONFIG, $dbcalls, $DB_PROFILE;
+            global $CONFIG, $dbcalls, $DB_PROFILE, $DB_QUERY_CACHE;
             
             $dblink = get_db_link('write');
             
@@ -244,7 +262,12 @@
             	$DB_PROFILE[] = $query;
             	
             	//error_log("--- DB QUERY --- $query");
-            }
+            }
+            
+            // Invalidate query cache
+            $DB_QUERY_CACHE = array();
+            if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            	error_log("Query cache invalidated");
             
             if (mysql_query("$query", $dblink)) 
                 return mysql_insert_id($dblink);
@@ -264,7 +287,7 @@
     
         function update_data($query) {
             
-            global $dbcalls, $CONFIG, $DB_PROFILE;
+            global $dbcalls, $CONFIG, $DB_PROFILE, $DB_QUERY_CACHE;
             
             $dblink = get_db_link('write');
             
@@ -275,7 +298,12 @@
             	$DB_PROFILE[] = $query; 
             	
             	//error_log("--- DB QUERY --- $query");
-            }
+            }
+            
+            // Invalidate query cache
+            $DB_QUERY_CACHE = array();
+            if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            	error_log("Query cache invalidated");
             
             if (mysql_query("$query", $dblink))
             	return true; //return mysql_affected_rows();
@@ -296,7 +324,7 @@
     
         function delete_data($query) {
             
-            global $dbcalls, $CONFIG, $DB_PROFILE;
+            global $dbcalls, $CONFIG, $DB_PROFILE, $DB_QUERY_CACHE;
             
             $dblink = get_db_link('write');
             
@@ -308,6 +336,11 @@
             	
             	//error_log("--- DB QUERY --- $query");
             }
+            
+            // Invalidate query cache
+            $DB_QUERY_CACHE = array();
+            if ((isset($CONFIG->debug)) && ($CONFIG->debug==true))
+            	error_log("Query cache invalidated");
             
             if (mysql_query("$query", $dblink)) 
                 return mysql_affected_rows();
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