Tom Lane 4526951d56 Make postgres_fdw's "Relations" output agree with the rest of EXPLAIN. ... The relation aliases shown in the "Relations" line for a foreign scan didn't always agree with those used in the rest of EXPLAIN's output. The regression test result changes appearing here provide examples. It's really impossible for postgres_fdw to duplicate EXPLAIN's alias assignment logic during postgresGetForeignRelSize(), because of the de-duplication that EXPLAIN does on a global basis --- and anyway, trying to duplicate that would be unmaintainable. Instead, just put numeric rangetable indexes into the string, and convert those to table names/aliases in postgresExplainForeignScan, which does have access to the results of ruleutils.c's alias assignment logic. Aside from being more reliable, this shifts some work from planning to EXPLAIN, which is a good tradeoff for performance. (I also changed from using StringInfo to using psprintf, which makes the code slightly simpler and reduces its memory consumption.) A kluge required by this solution is that we have to reverse-engineer the rtoffset applied by setrefs.c. If that logic ever fails (presumably because the member tables of a join got offset by different amounts), we'll need some more cooperation with setrefs.c to keep things straight. But for now, there's no need for that. Arguably this is a back-patchable bug fix, but since this is a mostly cosmetic issue and there have been no field complaints, I'll refrain for now. Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us		2019-12-02 16:31:03 -05:00
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postgres_fdw.out	Make postgres_fdw's "Relations" output agree with the rest of EXPLAIN.	2019-12-02 16:31:03 -05:00