Bumping it to attract some attention.
On Tue, Mar 21, 2023 at 12:51 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> Hi,
> Hash table scans (seq_scan_table/level) are cleaned up at the end of a
> transaction in AtEOXact_HashTables(). If a hash seq scan continues
> beyond transaction end it will meet "ERROR: no hash_seq_search scan
> for hash table" in deregister_seq_scan(). That seems like a limiting
> the hash table usage.
>
> Our use case is
> 1. Add/update/remove entries in hash table
> 2. Scan the existing entries and perform one transaction per entry
> 3. Close scan
>
> repeat above steps in an infinite loop. Note that we do not
> add/modify/delete entries in step 2. We can't use linked lists since
> the entries need to be updated or deleted using hash keys. Because the
> hash seq scan is cleaned up at the end of the transaction, we
> encounter error in the 3rd step. I don't see that the actual hash
> table scan depends upon the seq_scan_table/level[] which is cleaned up
> at the end of the transaction.
>
> I have following questions
> 1. Is there a way to avoid cleaning up seq_scan_table/level() when the
> transaction ends?
> 2. Is there a way that we can use hash table implementation in
> PostgreSQL code for our purpose?
>
>
> --
> Best Wishes,
> Ashutosh Bapat
--
Best Wishes,
Ashutosh Bapat
