Slow INSERTs to MEMORY table

[Rafal Plewa]

Hi,

I've a performance problem with "INSERT INTO ... SELECT FROM" statement. Internal SELECT statement is fast, it based on 10M rows table and returns results in 0.3 seconds.

The problem begins when I try to insert returned results (notice, that it's only 12k records!) to another temporary tabel with MEMORY engine using "INSERT INTO ... SELECT FROM" statement. A time of whole statement is more than 5 seconds. I would add that I run on fast (16 core, 24GB RAM) dedicated server. Temporary table has no indexes, and it's empty.

So, the question is why these INSERTs to MEMORY table are so slow? Maybe sb could help me to find a solution to improve timings of INSERTS.