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merge table - index cardinality
Posted by: d batz
Date: November 23, 2011 01:02AM

Hi MySQL community,

I need your help or some few advice. This is my first post in MySQL forum.
I made some changes on our database and i created a new merge table.
I noticed some weird numbers of Index on Merge table.

Example:
I have 20 tables complete with indexes.

Each table contains:
id1 BTREE CARDINALITY XXXXX
id2 BTREE CARDINALITY XXXXX
id3 BTREE CARDINALITY XXXXX
cardinality is good in each table.... the usual.


The "Merge table" contains:
id1 BTREE CARDINALITY 71 <--- huh??
id2 BTREE CARDINALITY 26 <--- huh??
id3 BTREE CARDINALITY 0 <--- huh??

The merge table is pretty NORMAL TO USE (columns and index declaration are ok... i assumed ). When I look at the index numbers is weird. I dunno where that numbers are from....
or is there something i lack ??????? XDDDD

i did some few tests, querying the merge bale. Sometimes fast, sometimes slow... .

BTW all total records around 1,500,000. When i target id1 and id2..... I hit 1 second more or less.

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