One thing I also tested was the performance of the in memory (HEAP) table type. I noticed that it used quite a bit more RAM. The 64-bit version uses about twice as much ram for the index_length, although the data_length was about the same. However, on disk the index and data file size were the same on 32-bit vs 64-bit. The key_buffer config variable is one of the most important config variables in mysql. If the 64-bit version is using twice as much ram for index buffering then its really holding half as many keys? Thats my guess but I could be wrong. I wonder if doubling the key_buffer size config var in the 64-bit version would change your query results. Mark Andreas Jaeger wrote:
One further note: You might want to compare these 3 scenarios:
- 64-bit mysql under 64-bit kernel - 32-bit mysql under 64-bit kernel - 32-bit mysql under 32-bit kernel
Andreas