[wp-trac] Re: [WordPress Trac] #5183: General Meta-Data Table

[WordPress Trac]

#5183: General Meta-Data Table
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 Reporter:  filosofo                     |        Owner:  anonymous     
     Type:  enhancement                  |       Status:  reopened      
 Priority:  normal                       |    Milestone:  Future Release
Component:  General                      |      Version:  2.9           
 Severity:  normal                       |   Resolution:                
 Keywords:  needs-patch meta-table meta  |  
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Comment(by Denis-de-Bernardy):

 Haven't tried MU in a while, but here's the current schema:

 http://trac.mu.wordpress.org/browser/trunk/wp-admin/includes/schema.php

 Re your prior question... To me, a "real" database means when the query
 engine decides that using an index can be faster than a seq scan. (Truth
 is, most databases are so small that the query optimizer will seq scan the
 bloody mess, since the table stats show it's faster to load all pages into
 the memory anyway.) Large is when having the correct indexes becomes
 meaningful (usually 50-100k rows). Very large means you're dead unless
 your indexes are optimized to fit your queries and data. That can be 100k
 to hundreds of millions of rows, depending on the app.

 As for the query you highlighted, it looks very yucky, but I'm guessing
 that the showcase.nid=%d will prompt the optimizer to return a nested loop
 plan. Whereas the odds are the optimizer will be merge joining its way
 through temporary files on the swap if you try the same with showcase.nid
 IN (..) on a few dozens of thousands of rows.

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Ticket URL: <http://core.trac.wordpress.org/ticket/5183#comment:36>
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