Re: Proposal: Recent mutated table tracking in memory

Hi Nadav,

Thank you for updating the patch!

> Thank you for the comments!
>
> I agree with all of them. Let me know what you think of the changes and new
> naming.

I still think "memory_map" is too generic. Anything put on memory for
data mapping could be called "memory map". I recommend to change the
name to more feature specific one: What about replacing "memory_map"
with "track_table_mutation"? It's a little bit longer name but it
clearly represents the feature. Any better ideas are welcome.

- memory_map_enabled: Enable/disable the feature (default: off)
- memory_map_ttl_factor: TTL multiplier for replication delay (default: 5.0)
- memory_map_cold_start_duration: Cold start period in ms (default: 2000)
- memory_map_table_buckets: Hash buckets for table map (default: 1024)
- memory_map_table_size: Max tracked tables (default: 2048)
- memory_map_query_buckets: Hash buckets for query cache (default: 2048)
- memory_map_query_cache_size: Max cached queries (default: 10000)

Also I feel memory_map_query_cache_size is confusing because there's
already "query cache" feature in pgpool. Can we change it something
like "query_parse_cache_size"?

Review comments:

(1) Why the regression test is 45? Shouldn't it be 42? (the last
feature test is 041.external_replication_delay).

(2) You enhance the patch to deal with leader watch changing. That's
good. However, I don't see a test case for it in test.sh.

(3) It seems the patch does not support TRUNCATE, MERGE, PREPARE and
WITH + updating. If so, it should be noted in the docs as a limitation
of the feature.
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
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