Re: [SQL] How match percent sign in SELECT using LIKE?

Good ideas. Added to TODO list.

> Bruce Momjian wrote:
> > I agree we should allow ESC, but that would make LIKE a trinary
> > operation, rather than a binary. If you want really confusing, the code
> > for LIKE really does:
> >
> > | a_expr LIKE a_expr
> > { $$ = makeIndexable("~~", $1, $3); }
> >
> > so it maps LIKE to a binary operator "~~". How do we map that into a
> > trinary operator, which we don't support? Doesn't really seem worth it.
> >
> > I can add an item to the TODO list if you wish?
>
> One useful and probably not too hard thing to do is to allow ESCAPE '\' on
> the end of the LIKE clause. Any character other than '\' will be an error.
> This allows Postgres users to write compliant SQL code that can be used
> with other databases.
>
> Another approach is to "rewrite" the match string at parse time. If it is a
> known constant, you can do the whole job there. Otherwise, you'd insert an
> extra node in the parse tree which does the rewrite just before calling hte
> "~~" operator. (I am assuming the match string can be a general expression
> and that you can add a function of two arguments which rewrites the first
> argument using the second argument as the escape character. This is of
> course not the utmost of micro efficiency, but I doubt it would matter
> much.)
>
> But I don't have in depth knowledge of the Postgres SQL parser and
> evaluator so I may be way off base.
>
> -Z-
>

--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026