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Hash/key Partition by something other than PK
Posted by: John Smith
Date: August 23, 2010 05:50AM

Is there any performance penalty or pit falls associated with hash/key partitioning by something other than the PK?

Say I have a table:

CREATE TABLE tweets (
tweet_id INT NOT NULL AUTO_INCREMENT,
author_id INT NOT NULL,
text CHAR(140) NOT NULL,
PRIMARY KEY (tweet_id)
)
PARTITION BY HASH(author_id)
PARTITIONS 12;

Will inserting new records into this table be any slower just because it is partitioned by author_id while the PK is a different field that is an auto-increment?

Also if I need to do a query like this:

SELECT *
FROM tweets
WHERE tweet_id=123

This query would require searching all partitions so it could be slow.

What if I modify the query into:

SELECT *
FROM tweets
WHERE tweet_id=123 AND author_id=33

The added condition "author_id=33" is unnecessary because the original condition "tweet_id=123" was enough to identify a unique record. But would this new query help MySQL to prune the partitions (only 1 partition satisfies the added condition of "author_id=33") and thus speed up the query?

Is MySQL capable of taking advantages of extra information like this to speed up query?

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Hash/key Partition by something other than PK
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August 23, 2010 05:50AM


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