Re: Primary key performance int vs. char
This is a good explanation. But it is valid only as long as no key packing happens (see reference manual 13.1.5. CREATE TABLE Syntax, Section "PACK_KEYS").
With packed keys, only the first key in the page is stored with its full value. All following keys with the same value use only one byte (plus the data pointer as for every key). A changing key value within a page is stored only with the value behind a common prefix and a byte telling how long the common prefix is. In this situation it is difficult to tell, which key will be faster.
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July 26, 2005 08:47PM
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