Re: Row pattern recognition

> Will continue reviewes tomorrow.

Sorry for delay. Here is the review for
v50-0005-match-once-per-row.patch.

--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -239,6 +239,10 @@ static int64 row_is_in_reduced_frame(WindowObject winobj, int64 pos);

static void clear_reduced_frame(WindowAggState *winstate);
static int get_reduced_frame_status(WindowAggState *winstate, int64 pos);
+static void advance_nav_mark(WindowAggState *winstate, int64 currentPos);
+static void advance_reduced_frame_nfa(WindowObject winobj,
+ RPRNFAContext *targetCtx, int64 pos,
+ bool hasLimitedFrame, int64 frameOffset);
static void update_reduced_frame(WindowObject winobj, int64 pos);

/* Forward declarations - NFA row evaluation */
@@ -2521,6 +2525,16 @@ ExecWindowAgg(PlanState *pstate)
{
if (winstate->rpSkipTo == ST_NEXT_ROW)
clear_reduced_frame(winstate);
+
+ /*
+ * Drive the row pattern match every row, so it tracks the row
+ * scan rather than frame access: a window function that skips
+ * the frame (e.g. nth_value() with a NULL offset) must not
+ * leave the match state behind currentpos.
+ */
+ Assert(winstate->nav_winobj != NULL);
+ (void) row_is_in_reduced_frame(winstate->nav_winobj,
+ winstate->currentpos);

Is there any reason that we call row_is_in_reduced_frame() here,
instead of something like:

update_frameheadpos(winstate);
update_reduced_frame(winobj, pos);

row_is_in_reduced_frame() returns row status. Ignoring it using (void)
looks a little bit confusing to me.

Regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
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