The docs are misleading for this feature, since they say: "This option disables all page-skipping behavior, and is intended to be used only when the contents of the visibility map are suspect, which should happen only if there is a hardware or software issue causing database corruption."
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The code is quite clear: DISABLE_PAGE_SKIPPING makes the vacuum into an aggressive vacuum. Line 487, heap_vacuum_rel(). Aggressive vacuums can still skip a page that is frozen, and rely on the visibility map for that information.
So the docs are wrong - we don't disable *all* page-skipping and it is not appropriate to warn users away from this feature by saying "is intended to be used only when the contents of the visibility map are suspect".
This patch seems mis-placed, at least in HEAD. If DISABLE_PAGE_SKIPPING isn't doing what the documentation says it should, but instead provides identical behavior to FREEZE, then the bug should be fixed in HEAD. I'd argue for batch-patching it as well.
