1. Parsing Strange:URL to SQL to HTML Hal Stern snowmanonfire.comslideshare.net/freeholdhal headshot by Richard Stevenshttp://dieselsweeties.com

2. Why Do You Care? Database performance = user experience A little database expertise goes a long way Taxonomies for more than sidebar lists Custom post types WordPress as a powerful CMS >> blog Change default behaviors Defy the common wisdom Integrate other content sources/filters WordCamp NYC 2010 2

3. Flow of Control Web server URL manipulation Real file or permalink URL? URL to query variables What to display? Tag? Post? Category? Query variables to SQL generation How exactly to get that content? Template file selection How will content be displayed? Content manipulation 3 WordCamp NYC 2010

4. Whose File Is This? User URL request passed to web server Web server checks.htaccessfile WP install root Other .htaccessfiles may interfere Basic rewriting rules:If file or directory URL doesn’t exist, start WordPress via index.php WordCamp NYC 2010 4 <IfModulemod_rewrite.c> RewriteEngine On RewriteBase /whereyouputWordPress/ RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule>

5. Example Meta Fail: 404 Not Found Access broken image URLs for unintended results: no 404 pages!myblog/images/not-a-pic.jpg Web server can’t find file, assumes it’s a permalink, hands to WP WP can’t interpret it, so defaults to home WordCamp NYC 2010 5 myblog/ myblog/wp-content (etc) myblog/images

6. What Happens Before The Loop Parse URL into a query Set conditionals & select templates Execute the query & cache results Run the Loop:<?phpif (have_posts()) : while (have_posts()) : the_post(); //loop contentendwhile;endif;?> WordCamp NYC 2010 6

7. Examining the Query String SQL passed to MySQL in WP_Query object’s request element Brute force: edit theme footer.phpto see main loop’s query for displayed page WordCamp NYC 2010 7 <?php global $wp_query; echo ”SQL for this page "; echo $wp_query->request; echo "<br>"; ?>

8. SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post’ AND(wp_posts.post_status = 'publish' ORwp_posts.post_status = 'private’)ORDER BY wp_posts.post_date DESC LIMIT 0, 10 “Home Page” Query Deconstruction WordCamp NYC 2010 8 Get all fields from posts table, but limit number of returned rows Only get posts, and those that are published or private to the user Sort the results by date in descending order Start results starting with record 0 and up to 10 more results

9. Query Parsing parse_request() method of WP_Query extracts query variables from URL Execute rewrite rules Pick off ?p=67 style http GET variables Match permalink structure Match keywords like “author” and “tag” Match custom post type slugs WordCamp NYC 2010 9

10. Query Variables to SQL Query type: post by title, posts by category or tag, posts by date Variables for the query Slug values for category/tags Month/day numbers Explicit variable values post_typevariable has been around for a while; CPT queries fill in new values WordCamp NYC 2010 10

11. Simple Title Slug Parsing Rewrite matches root of permalink, extracts tail of URL as a title slug WordCamp NYC 2010 11 /2010/premio-sausage SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND YEAR(wp_posts.post_date)='2010' AND wp_posts.post_name = 'premio-sausage' AND wp_posts.post_type = 'post' ORDER BY wp_posts.post_date DESC

12. CPT Query Variables Register CPT with a custom query variable 'query_var' => 'ebay' Variable works in URLs like built-ins myblog.com/?ebay=current_items myblog.com/?ebay=cool_searches Variable value matches CPT title slug WordCamp NYC 2010 12

13. WordPress Meta Data Common DB mechanics for all meta data Categories, tags, custom taxonomies Normalized down to 3 tables Terms: word strings and their slugs Taxonomies: collections of terms Relationships: terms attached to posts It’s so simple it gets really complex. Really. WordCamp NYC 2010 13

14. Graphs and JOIN Operations WordPress maps tags and categories 1:N to posts (each term in many posts) You need to punch MySQL to handle this INNER JOIN builds intermediate tables on common key values Following link in a graph is equivalent to an INNER JOIN on tables of linked items WordCamp NYC 2010 14

15. WordPress Taxonomy Tables Term relationships table maps N terms to each post Term taxonomy maps N terms to each taxonomy Term table has slugs for URL mapping WordCamp NYC 2010 15 wp_term_relationshipsobject_idterm_taxonomy_id wp_postspost_id….post_date… post_content wp_term_taxonomyterm_taxonomy_idterm_idtaxonomydescription wp_terms term_idnameslug

16. SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_postsINNER JOIN wp_term_relationships ON(wp_posts.ID = wp_term_relationships.object_id)INNER JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id)INNER JOIN wp_terms ON (wp_term_taxonomy.term_id = wp_terms.term_id)WHERE 1=1 AND wp_term_taxonomy.taxonomy = 'post_tag' AND wp_terms.slug IN ('premio') AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 10 Taxonomy Lookup WordCamp NYC 2010 16 /tag/premio

17. More on Canonical URLs Canonical URLs improve SEO WordPress is really good about generating 301 Redirects for non-standard URLs Example: URL doesn’t appear to match a permalink, WordPress does prediction Use “LIKE title%” in WHERE clause Matches “title” as initial substring with % wildcard WordCamp NYC 2010 17

18. Modifying the Query Brute force isn’t necessarily good Using query_posts() ignores all previous parsing, runs a new SQL query Filter query_vars Change default parsing (convert any day to a week’s worth of posts, for example) Actions parse_query & parse_request Access WP_Query object before execution is_xx() conditionals are already set WordCamp NYC 2010 18

19. SQL Generation Filters posts_where More explicit control over query variable to SQL grammar mapping posts_join Add or modify JOIN operations for other graph relationships Many other filters Change grouping of results Change ordering of results WordCamp NYC 2010 19

20. Custom Post Types Change SQL WHERE clause on post type wp_posts.post_type=‘ebay’ Add new rewrite rules for URL parsing similar to category & tag Set slug in CPT registration array'rewrite' => array ("slug" => “ebay”), Watch out for competing, overwritten or unflushed rewrite entries<?php echo "<pre>”;print_r(get_option('rewrite_rules'));echo "</pre>”;?> WordCamp NYC 2010 20

21. Applications Stylized listings Category sorted alphabetically Use posts as listings of resources (jobs, clients, events) – good CPT application Custom URL slugs Add rewrite rules to match slug and set query variables Joining other social graphs Suggested/related content WordCamp NYC 2010 21

22. Template File Selection is_x() conditionals set in query parsing Used to drive template selection is_tag() looks for tag-slug, tag-id, then tag Full search hierarchy in Codex template_redirectaction Called in the template loader Add actions to override defaults WordCamp NYC 2010 22

23. HTML Generation Done in the_post() method Raw content retrieved from MySQL Short codes interpreted CSS applied Some caching plugins generate and store HTML, so YMMV WordCamp NYC 2010 23

24. Why Do You Care? User experience improvement JOINS are expensive Large post table & repetitive SELECTs = slow Running query once keeps cache warm Category, permalink, title slug choices matter More CMS, less “blog” Alphabetical sort Adding taxonomy/social graph elements WordCamp NYC 2010 24

25. Resources Core files where SQL stuff happens query.php post.php canonical.php rewrite.php Template loader search path http://codex.wordpress.org/Template_Hierarchy WordCamp NYC 2010 25

26. Contact Hal Stern freeholdhal@gmail.com @freeholdhal snowmanonfire.com facebook.com/hal.stern Other Projects: amphibimen.com facebook.com/letusin slideshare.net/freeholdhal WordCamp NYC 2010 26