[pgpool-hackers: 2338] Re: PostgreSQL 10 backward incompatibilities

[Tatsuo Ishii]

>> From the PostgreSQL 10 relelease note:
>>
>> Rename SQL functions, tools, and options that reference “xlog” to “wal”
>> (Robert Haas)
>>
>> This surely affects to Pgpool-II. I found these calls in Pgpool-II:
>>
>>                 query = "SELECT pg_current_xlog_location()";
>>                 query = "SELECT pg_last_xlog_replay_location()";
>>
>> We have to deal with this. Just changing these function names to new
>> ones will make Pgpool-II not work with pre-10 versions of
>> PostgreSQL. So will not be acceptable. Any idea?
>>
> 
> I think these calls are only made by pgpool-worker child process, So one
> way could be to get the server version of each attached backend at the
> child startup (SELECT current_setting('server_version_num'))  and store the
> version for each backend node in respective backend data structure.
> And latter before sending the query we can construct the appropriate query
> by looking at the version information for that backend.

server_version_num appeared in PostgreSQL 8.2. Since those functions
are only used in streaming replication, which first appeared in 9.6,
we can safely your method. Nice idea!

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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