Re: Identifying no-op length coercions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org, Robert Haas <robertmhaas(at)gmail(dot)com>, Alexey Klyukin <alexk(at)commandprompt(dot)com>
Subject: Re: Identifying no-op length coercions
Date: 2011-06-11 19:03:18
Message-ID: 20117.1307818998@sss.pgh.pa.us
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Noah Misch <noah(at)leadboat(dot)com> writes:
> Good points. I'm thinking, then, add an Expr argument to simplify_function()
> and have the CoerceViaIO branch of eval_const_expressions_mutator() pass NULL
> for both its simplify_function() calls. If simplify_function() gets a NULL Expr
> for a function that has a protransform, synthesize a FuncExpr based on its other
> arguments before calling the transform function. Seem reasonable? Granted,
> that would be dead code until someone applies a transform function to a type I/O
> function, which could easily never happen. Perhaps just ignore the transform
> function when we started with a CoerceViaIO node?

Until we actually have a use-case for simplifying I/O functions like this,
I can't see going out of our way for it ...

regards, tom lane

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