On Tue, 16 Apr 2024 at 14:52, Alexander Korotkov <aekorot...@gmail.com> wrote:
> On Mon, Apr 15, 2024 at 11:17 PM Andres Freund <and...@anarazel.de> wrote: > > On 2024-04-15 16:02:00 -0400, Robert Haas wrote: > > > Do you want that patch applied, not applied, or applied with some set > of > > > modifications? > > > > I think we should apply Alexander's proposed revert and then separately > > discuss what we should do about 041b96802ef. > > Taking a closer look at acquire_sample_rows(), I think it would be > good if table AM implementation would care about block-level (or > whatever-level) sampling. So that acquire_sample_rows() just fetches > tuples one-by-one from table AM implementation without any care about > blocks. Possible table_beginscan_analyze() could take an argument of > target number of tuples, then those tuples are just fetches with > table_scan_analyze_next_tuple(). What do you think? > Hi, Alexander! I like the idea of splitting abstraction levels for: 1. acquirefuncs (FDW or physical table) 2. new specific row fetch functions (alike to existing _scan_analyze_next_tuple()), that could be AM-specific. Then scan_analyze_next_block() or another iteration algorithm would be contained inside table AM implementation of _scan_analyze_next_tuple(). So, init of scan state would be inside table AM implementation of _beginscan_analyze(). Scan state (like BlockSamplerData or other state that could be custom for AM) could be transferred from _beginscan_analyze() to _scan_analyze_next_tuple() by some opaque AM-specific data structure. If so we'll also may need AM-specific table_endscan_analyze to clean it. Regards, Pavel
