Alvaro Herrera <alvhe...@2ndquadrant.com> writes: > Tom Lane wrote: >> A difficulty with either your patch or my idea is that they require adding >> another field to ExplainState, which is an ABI break for any third-party >> code that might be declaring variables of that struct type. That's fine >> for HEAD but would be risky to back-patch. Any thoughts about whether we >> can get away with that (ie, anybody have an idea if there are third-party >> extensions that call explain.c)?
> codesearch.debian.net shows a couple of hits for ExplainState in > multicorn (an extension for FDW from Python data sources); I didn't look > but it seems that the FDW API is using that struct. It is, but FDWs are not at risk here: they merely reference ExplainStates that were allocated by core backend code. So as long as we add the new field at the end it's not a problem for them. Problematic usage would be like what auto_explain does: ExplainState es; ExplainInitState(&es); ... In hindsight, that's a bad API and we should change it to something like ExplainState *es = NewExplainState(); so that the sizeof the struct isn't embedded in extension code. But we definitely can't do that in back branches. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers