Tom Lane wrote:
Andrew Dunstan <[EMAIL PROTECTED]> writes:
My instinct would be to follow your first strategy, i.e. detect which path is needed rather than try one and then if it fails do the other.

The very first thing you need to think about is how to solve the race
condition problem, ie, two backends concurrently trying to insert
identical data.  Until you have a plausible mechanism for that, the
whole thing is pie-in-the-sky.

How about:

1. Insert new heap tuple
2. Try to insert the index tuple. If there's a duplicate tuple, lock the existing tuple instead of throwing an error.
3. If there was no duplicate, we're done.

4. Otherwise, kill the new tuple inserted in step 1, by setting it's xmin to InvalidTransactionId.
5. Perform the UPDATE on the existing tuple.

This requires one change to the indexam api: a duplicate key violation needs to lock the existing tuple instead of throwing an error.

  Heikki Linnakangas

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