On Mon, 15 Jul 2019 at 17:54, Edmund Horner <ejr...@gmail.com> wrote: > Summary of changes compared to last time: > - I've added the additional "scan_setlimits" table AM method. To > check whether it's implemented in the planner, I have added an > additional "has_scan_setlimits" flag to RelOptInfo. It seems to work. > - I've also changed nodeTidrangescan to not require anything from heapam > now. > - To simply the patch and avoid changing heapam, I've removed the > backward scan support (which was needed for FETCH LAST/PRIOR) and made > ExecSupportsBackwardScan return false for this plan type. > - I've removed the vestigial passing of "direction" through > nodeTidrangescan. If my understanding is correct, the direction > passed to TidRangeNext will always be forward. But I did leave FETCH > LAST/PRIOR in the regression tests (after adding SCROLL to the > cursor).
I spent some time today hacking at this. I fixed a bug in how has_scan_setlimits set, rewrite a few comments and simplified some of the code. When I mentioned up-thread about the optional scan_setlimits table AM callback, I'd forgotten that you'd not have access to check that directly during planning. As you mention above, you've added RelOptInfo has_scan_setlimits so the planner knows if it can use TID Range scans or not. It would be nice to not have to add this flag, but that would require either: 1. Making scan_setlimits a non-optional callback function in table AM, or; 2. Allowing the planner to have access to the opened Relation. #2 is not for this patch, but there has been some talk about it. It was done for the executor last year in d73f4c74dd3. I wonder if Andres has any thoughts on #1? The other thing I was thinking about was if enable_tidscan should be in charge of TID Range scans too. I see you have it that way, but should we be adding enable_tidrangescan? The docs claim that enable_tidscan: "Enables or disables the query planner's use of TID scan plan types.". Note: "types" is plural. Maybe we could call that fate and keep it the way the patch has it already. Does anyone have another idea about that? I've attached a delta of the changes I made and also a complete v9 patch. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
v8_to_v9_delta.patch
Description: Binary data
v9_tid_range_scans.patch
Description: Binary data
