Re: pgsql: Pull up isReset flag from AllocSetContext to MemoryContext struc

Heikki Linnakangas <heikki.linnakangas@iki.fi> writes:
> Pull up isReset flag from AllocSetContext to MemoryContext struct. This
> avoids the overhead of one function call when calling MemoryContextReset(),
> and it seems like the isReset optimization would be applicable to any new
> memory context we might invent in the future anyway.

> This buys back the overhead I just added in previous patch to always call
> MemoryContextReset() in ExecScan, even when there's no quals or projections.

Do you actually have any measurements that prove that?  This seems like
a rather ugly destruction of a modularity boundary in return for a
hypothetical performance gain.  I'm also concerned that you've probably
added cycles on net to MemoryContextAlloc (where it's no longer possible
to tail-call AllocSetAlloc), which could very easily cost more cycles on
most workloads than could ever be saved by making MemoryContextReset a
shade faster.

            regards, tom lane