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Pruning with HASH or KEY
Posted by: Shlomi Noach
Date: August 19, 2006 12:50AM

Hello, everyone,

In the latest article on developer zone, "MySQL 5.1 New Features: MySQL Partitions", the writer says that "Pruning is good with RANGE and LIST partitions, irrelevant with HASH and KEY partitions".

However, on MySQL 5.1 reference manual, http://mysql.com/doc/refman/5.1/en/partitioning-pruning.html, it says: "For tables that are partitioned by HASH or KEY, partition pruning is also possible. However, it can be used only on integer columns of tables using these partitioning types..."

Which of the two is correct?

I have a table my_table which I partition by HASH over an int field my_field (which is, accidently, one of the keys for the table - it has an index - but not the primary key).
Will MySQL perform pruning when I query:
SELECT * FROM my_table WHERE my_field = 1234 AND other_field = 5678 AND ...
?

Is there a general way (such as in EXPLAIN SELECT) to know in advance if MySQL will perform pruning?

Thanks in advance,
Shlomi

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