| Lists: | pgsql-bugs |
|---|
| From: | Neil Conway <neilc(at)samurai(dot)com> |
|---|---|
| To: | pgsql-bugs(at)postgresql(dot)org |
| Subject: | expression_tree_walker() and primitive node types |
| Date: | 2007-10-12 06:16:43 |
| Message-ID: | 1192169803.9420.6.camel@goldbach |
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| Lists: | pgsql-bugs |
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.
| 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 |
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| 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