SQL fixed-value IN() vs. INNER JOIN performance

Question

In answer to this SQL question, I\'ve encountered a statement that fixed-value IN() operator is much slower than INNER JOIN with the same content,

Answer 1

This relates to the length of the IN clause - and what is sometimes called a BUG in MySQL.

MySQL seems to have a low threshold for IN clauses, when it will swap to a TABLE/INDEX SCAN instead of collecting multiple partitions (one per IN item) and merging them.

With an INNER JOIN, it is almost always forced to use a direct row-by-row in JOIN collection, which is why it is sometimes faster

Refer to these MySQL manual pages

• In Subquery considerations
• In (constant list) performance

I could be wrong since it seems to imply that IN (constant value list) should always use a binary search on each item...