Re: bind variables, soft vs hard parse

In some cases, Oracle will also replace literals with bind variables so that
it can perform a sort-of-bind-value soft parse later.

On 11/15/05, Jim C. Nasby <jnasby(at)pervasive(dot)com> wrote:
>
> PostgreSQL combines both parses into one, so every new query is
> effectively a hard parse (unless it's prepared, then there is no parse
> or optimization at all).
>
> On Tue, Nov 15, 2005 at 07:33:46PM +0100, Marcus Engene wrote:
> > Hi list.
> >
> > I've mostly used Oracle in the past, but for a web-project I took the
> > opportunity to try Postgres.
> >
> > When a select is done in Oracle, it first checks if the select is cached
> > (ie parsed tree, optimizer choices & such). It does this by
> > [functionality equal to] a byte to byte compare with the other sql
> strings.
> >
> > select a from b where c = 1
> > select a from b where c = 2
> >
> > ...will thus force a hard parse on the second select. But if using bind
> > variables it wont as the string stored is something like
> >
> > select a from b where c = ?
> >
> > Which will be the same as the second call. There is quite a big
> > difference in performance using bind variables.
> >
> > Does Postgres work the same? Where can I go for more info?
> >
> > Oracle recently gave some money to Zend to make proper Oracle support
> > for PHP. In that interface they use bind variables. Apart from greater
> > speed, sqlinjection becomes history as well.
> >
> > Best regards,
> > Marcus
> >
> >
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>
> --
> Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
> Pervasive Software http://pervasive.com work: 512-231-6117
> vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
>
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