From 2067d1a727e7eb5e5ffb40e967f3d1fc4c8a41b2 Mon Sep 17 00:00:00 2001 From: Derek Allard Date: Thu, 13 Nov 2008 22:59:24 +0000 Subject: Changing EOL style to LF --- user_guide/database/caching.html | 438 +++++++++++++++++++-------------------- 1 file changed, 219 insertions(+), 219 deletions(-) (limited to 'user_guide/database/caching.html') diff --git a/user_guide/database/caching.html b/user_guide/database/caching.html index 9016ffe06..485d7f4c3 100644 --- a/user_guide/database/caching.html +++ b/user_guide/database/caching.html @@ -1,220 +1,220 @@ - - - - - -Database Caching Class : CodeIgniter User Guide - - - - - - - - - - - - - - - - - - - - - -
- - - - - -

CodeIgniter User Guide Version 1.7

-
- - - - - - - - - -
- - - -
- - - -
- -

Database Caching Class

- -

The Database Caching Class permits you to cache your queries as text files for reduced database load.

- -

Important:  This class is initialized automatically by the database driver -when caching is enabled. Do NOT load this class manually.

- -Also note:  Not all query result functions are available when you use caching. Please read this page carefully.

- -

Enabling Caching

- -

Caching is enabled in three steps:

- - - -

Once enabled, caching will happen automatically whenever a page is loaded that contains database queries.

- - -

How Does Caching Work?

- -

CodeIgniter's query caching system happens dynamically when your pages are viewed. -When caching is enabled, the first time a web page is loaded, the query result object will -be serialized and stored in a text file on your server. The next time the page is loaded the cache file will be used instead of -accessing your database. Your database usage can effectively be reduced to zero for any pages that have been cached.

- -

Only read-type (SELECT) queries can be cached, since these are the only type of queries that produce a result. -Write-type (INSERT, UPDATE, etc.) queries, since they don't generate a result, will not be cached by the system.

- -

Cache files DO NOT expire. Any queries that have been cached will remain cached until you delete them. The caching system -permits you clear caches associated with individual pages, or you can delete the entire collection of cache files. -Typically you'll want to use the housekeeping functions described below to delete cache files after certain -events take place, like when you've added new information to your database.

- -

Will Caching Improve Your Site's Performance?

- -

Getting a performance gain as a result of caching depends on many factors. -If you have a highly optimized database under very little load, you probably won't see a performance boost. -If your database is under heavy use you probably will see an improved response, assuming your file-system is not -overly taxed. Remember that caching simply changes how your information is retrieved, shifting it from being a database -operation to a file-system one.

- -

In some clustered server environments, for example, caching may be detrimental since file-system operations are so intense. -On single servers in shared environments, caching will probably be beneficial. Unfortunately there is no -single answer to the question of whether you should cache your database. It really depends on your situation.

- -

How are Cache Files Stored?

- -

CodeIgniter places the result of EACH query into its own cache file. Sets of cache files are further organized into -sub-folders corresponding to your controller functions. To be precise, the sub-folders are named identically to the -first two segments of your URI (the controller class name and function name).

- -

For example, let's say you have a controller called blog with a function called comments that -contains three queries. The caching system will create a cache folder -called blog+comments, into which it will write three cache files.

- -

If you use dynamic queries that change based on information in your URI (when using pagination, for example), each instance of -the query will produce its own cache file. It's possible, therefore, to end up with many times more cache files than you have -queries.

- - -

Managing your Cache Files

- -

Since cache files do not expire, you'll need to build deletion routines into your application. For example, let's say you have a blog -that allows user commenting. Whenever a new comment is submitted you'll want to delete the cache files associated with the -controller function that serves up your comments. You'll find two delete functions described below that help you -clear data.

- - -

Not All Database Functions Work with Caching

- -

Lastly, we need to point out that the result object that is cached is a simplified version of the full result object. For that reason, -some of the query result functions are not available for use.

- -

The following functions ARE NOT available when using a cached result object:

- - - -

Also, the two database resources (result_id and conn_id) are not available when caching, since result resources only -pertain to run-time operations.

- - -
- -

Function Reference

- - - -

$this->db->cache_on()  /   $this->db->cache_off()

- -

Manually enables/disables caching. This can be useful if you want to -keep certain queries from being cached. Example:

- - -// Turn caching on
-$this->db->cache_on();
-$query = $this->db->query("SELECT * FROM mytable");
-
-// Turn caching off for this one query
-$this->db->cache_off();
-$query = $this->db->query("SELECT * FROM members WHERE member_id = '$current_user'");
-
-// Turn caching back on
-$this->db->cache_on();
-$query = $this->db->query("SELECT * FROM another_table"); - - - -

$this->db->cache_delete()

- -

Deletes the cache files associated with a particular page. This is useful if you need to clear caching after you update your database.

- -

The caching system saves your cache files to folders that correspond to the URI of the page you are viewing. For example, if you are viewing -a page at example.com/index.php/blog/comments, the caching system will put all cache files associated with it in a folder -called blog+comments. To delete those particular cache files you will use:

- -$this->db->cache_delete('blog', 'comments'); - -

If you do not use any parameters the current URI will be used when determining what should be cleared.

- - -

$this->db->cache_delete_all()

- -

Clears all existing cache files. Example:

- -$this->db->cache_delete_all(); - - - - - - - - - - -
- - - - - - + + + + + +Database Caching Class : CodeIgniter User Guide + + + + + + + + + + + + + + + + + + + + + +
+ + + + + +

CodeIgniter User Guide Version 1.7

+
+ + + + + + + + + +
+ + + +
+ + + +
+ +

Database Caching Class

+ +

The Database Caching Class permits you to cache your queries as text files for reduced database load.

+ +

Important:  This class is initialized automatically by the database driver +when caching is enabled. Do NOT load this class manually.

+ +Also note:  Not all query result functions are available when you use caching. Please read this page carefully.

+ +

Enabling Caching

+ +

Caching is enabled in three steps:

+ + + +

Once enabled, caching will happen automatically whenever a page is loaded that contains database queries.

+ + +

How Does Caching Work?

+ +

CodeIgniter's query caching system happens dynamically when your pages are viewed. +When caching is enabled, the first time a web page is loaded, the query result object will +be serialized and stored in a text file on your server. The next time the page is loaded the cache file will be used instead of +accessing your database. Your database usage can effectively be reduced to zero for any pages that have been cached.

+ +

Only read-type (SELECT) queries can be cached, since these are the only type of queries that produce a result. +Write-type (INSERT, UPDATE, etc.) queries, since they don't generate a result, will not be cached by the system.

+ +

Cache files DO NOT expire. Any queries that have been cached will remain cached until you delete them. The caching system +permits you clear caches associated with individual pages, or you can delete the entire collection of cache files. +Typically you'll want to use the housekeeping functions described below to delete cache files after certain +events take place, like when you've added new information to your database.

+ +

Will Caching Improve Your Site's Performance?

+ +

Getting a performance gain as a result of caching depends on many factors. +If you have a highly optimized database under very little load, you probably won't see a performance boost. +If your database is under heavy use you probably will see an improved response, assuming your file-system is not +overly taxed. Remember that caching simply changes how your information is retrieved, shifting it from being a database +operation to a file-system one.

+ +

In some clustered server environments, for example, caching may be detrimental since file-system operations are so intense. +On single servers in shared environments, caching will probably be beneficial. Unfortunately there is no +single answer to the question of whether you should cache your database. It really depends on your situation.

+ +

How are Cache Files Stored?

+ +

CodeIgniter places the result of EACH query into its own cache file. Sets of cache files are further organized into +sub-folders corresponding to your controller functions. To be precise, the sub-folders are named identically to the +first two segments of your URI (the controller class name and function name).

+ +

For example, let's say you have a controller called blog with a function called comments that +contains three queries. The caching system will create a cache folder +called blog+comments, into which it will write three cache files.

+ +

If you use dynamic queries that change based on information in your URI (when using pagination, for example), each instance of +the query will produce its own cache file. It's possible, therefore, to end up with many times more cache files than you have +queries.

+ + +

Managing your Cache Files

+ +

Since cache files do not expire, you'll need to build deletion routines into your application. For example, let's say you have a blog +that allows user commenting. Whenever a new comment is submitted you'll want to delete the cache files associated with the +controller function that serves up your comments. You'll find two delete functions described below that help you +clear data.

+ + +

Not All Database Functions Work with Caching

+ +

Lastly, we need to point out that the result object that is cached is a simplified version of the full result object. For that reason, +some of the query result functions are not available for use.

+ +

The following functions ARE NOT available when using a cached result object:

+ + + +

Also, the two database resources (result_id and conn_id) are not available when caching, since result resources only +pertain to run-time operations.

+ + +
+ +

Function Reference

+ + + +

$this->db->cache_on()  /   $this->db->cache_off()

+ +

Manually enables/disables caching. This can be useful if you want to +keep certain queries from being cached. Example:

+ + +// Turn caching on
+$this->db->cache_on();
+$query = $this->db->query("SELECT * FROM mytable");
+
+// Turn caching off for this one query
+$this->db->cache_off();
+$query = $this->db->query("SELECT * FROM members WHERE member_id = '$current_user'");
+
+// Turn caching back on
+$this->db->cache_on();
+$query = $this->db->query("SELECT * FROM another_table"); + + + +

$this->db->cache_delete()

+ +

Deletes the cache files associated with a particular page. This is useful if you need to clear caching after you update your database.

+ +

The caching system saves your cache files to folders that correspond to the URI of the page you are viewing. For example, if you are viewing +a page at example.com/index.php/blog/comments, the caching system will put all cache files associated with it in a folder +called blog+comments. To delete those particular cache files you will use:

+ +$this->db->cache_delete('blog', 'comments'); + +

If you do not use any parameters the current URI will be used when determining what should be cleared.

+ + +

$this->db->cache_delete_all()

+ +

Clears all existing cache files. Example:

+ +$this->db->cache_delete_all(); + + + + + + + + + + +
+ + + + + + \ No newline at end of file -- cgit v1.2.3-24-g4f1b