| From: | Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Peter van Hardenberg <pvh(at)pvh(dot)ca>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Patch: Implement failover on libpq connect level. |
| Date: | 2016-11-16 04:31:54 |
| Message-ID: | CAD__OujrhLNB6QtWLxZtvJt5n=gT+waWtRMLSLk=7J+fiOAFqg@mail.gmail.com |
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| Lists: | pgsql-hackers pgsql-jdbc |
>
> > So I am tempted to just
> > hold my nose and hard-code the SQL as JDBC is presumably already
> doing.
JDBC is sending "show transaction_read_only" to find whether it is master
or not.
Victor's patch also started with it, but later it was transformed into
pg_is_in_recovery
by him as it appeared more appropriate to identify the master / slave.
ConnectionFactoryImpl.java:685
+ private boolean isMaster(QueryExecutor queryExecutor, Logger logger)
+ throws SQLException, IOException {
+ byte[][] results = SetupQueryRunner.run(queryExecutor, "show
transaction_read_only", true);
+ String value = queryExecutor.getEncoding().decode(results[0]);
+ return value.equalsIgnoreCase("off");
}
--
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com
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