On Mon, Apr 30, 2001 at 01:11:21AM -0400, Tom Lane wrote:
> Always remember that the cost estimates quoted by EXPLAIN are estimates,
> not reality.
>
> In this case the reason for the difference is that the planner doesn't
> have any detailed understanding of the semantics of bracket-expressions
> in regexps, so it doesn't realize that ^[AB] could usefully use an
> index. It wants to see ^ followed by at least one character of fixed
> pattern before it will think about an indexscan ...
so the query planner doesn't use indexes for ~'^[A-F]' then?
(meaning, such regex queries are all sequential scans...)
or are you saying that just the explainer routines don't?
(meaning, explain doesn't grok as well as the actual fetch-
and-match routines do...)
hmm?
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