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Remove dead NoMovementScanDirection code

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Here remove some dead code from heapgettup() and heapgettup_pagemode()
which was trying to support NoMovementScanDirection scans.  This code can
never be reached as standard_ExecutorRun() never calls ExecutePlan with
NoMovementScanDirection.

Additionally, plans which were scanning an unordered index would use
NoMovementScanDirection rather than ForwardScanDirection.  There was no
real need for this, so here we adjust this so we use ForwardScanDirection
for unordered index scans.  A comment in pathnodes.h claimed that
NoMovementScanDirection was used for PathKey reasons, but if that was
true, it no longer is, per code in build_index_paths().

This does change the non-text format of the EXPLAIN output so that
unordered index scans now have a "Forward" scan direction rather than
"NoMovement".  The text format of EXPLAIN has not changed.

Author: Melanie Plageman
Reviewed-by: Tom Lane, David Rowley
Discussion: https://postgr.es/m/CAAKRu_bvkhka0CZQun28KTqhuUh5ZqY=_T8QEqZqOL02rpi2bw@mail.gmail.com
This commit is contained in:
David Rowley
2023-02-01 10:52:41 +13:00
parent 856ca51a23
commit e9aaf06328
10 changed files with 43 additions and 102 deletions
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7
src/include/nodes/pathnodes.h
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@@ -1672,12 +1672,9 @@ typedef struct Path
* on which index column each ORDER BY can be used with.)
*
* 'indexscandir' is one of:
* ForwardScanDirection: forward scan of an ordered index
* ForwardScanDirection: forward scan of an index
* BackwardScanDirection: backward scan of an ordered index
* NoMovementScanDirection: scan of an unordered index, or don't care
* (The executor doesn't care whether it gets ForwardScanDirection or
* NoMovementScanDirection for an indexscan, but the planner wants to
* distinguish ordered from unordered indexes for building pathkeys.)
* Unordered indexes will always have an indexscandir of ForwardScanDirection.
*
* 'indextotalcost' and 'indexselectivity' are saved in the IndexPath so that
* we need not recompute them when considering using the same index in a