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Re: expression_tree_walker() and primitive node types

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: expression_tree_walker() and primitive node types
Date: 2007-10-12 14:23:17
Message-ID: 26246.1192198997@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Neil Conway <neilc(at)samurai(dot)com> writes:
> I wouldn't call this behavior buggy, but I found it somewhat surprising.
> expression_tree_walker() assumes that the walker has already been
> invoked on the current node (the node that a given recursive call of
> expression_tree_walker() has been invoked on). Therefore, calling
> expression_tree_walker() on a primitive node type, such as a Var, is a
> no-op.

The documented usage method is to call the walker itself at the top
level of recursion.  The walker calls expression_tree_walker (after
doing its thing on the node); other code should not call
expression_tree_walker directly.

			regards, tom lane

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