[Patch] RBTree iteration interface improvement

From: Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>
To: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: [Patch] RBTree iteration interface improvement
Date: 2016-07-27 14:26:45
Message-ID: 20160727172645.3180b2e0@fujitsu
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Hello

While working on some new feature for PostgreSQL (which is still in
development and is irrelevant in this context) I noticed that current
RBTree implementation interface is following:

```
extern void rb_begin_iterate(RBTree *rb, RBOrderControl ctrl);
extern RBNode *rb_iterate(RBTree *rb);
```

As you see it doesn't allow to do multiple iterations over a single
tree. I believe it's a major flaw for a general-purpose container.

Proposed patch introduces a new iteration interface that doesn't has
such a flaw. Naturally I wrote some unit tests, but I was not sure where
exactly to place them in PostgreSQL source code. For now I've just
uploaded them to GitHub:

https://github.com/afiskon/c-algorithms-examples/blob/master/rbtree_example.c

According to these tests new implementation works as fast as current
implementation and produces exactly same results.

I didn't dare to remove current interface since in theory some
extensions can use it. Still I believe such a move is worth considering.

--
Best regards,
Aleksander Alekseev

Attachment Content-Type Size
rbtree-iteration-improvement.patch text/x-patch 8.6 KB

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