Hi, I spent some time trying to create a repro (other than testing it on the
production instance where we encountered the bug), but was unable to create one
within a reasonable time.
The tricky part is that the bug symptoms are run-time symptoms -- so not only
do you need, first, to satisfy conditions (1), (2), and (3), without the query
optimizer optimizing them away! -- but you also need, second, a query that runs
long enough for one or more of the parallel workers' state machines to get
confused. (This wasn't a problem on the production instance where we
encountered the bug and I tested the fix.)
Also, third-- passing InvalidBlockNumber to ReadBuffer() generally just appends
a new block to the relation, so the bug doesn't even result in an error
condition on an RW instance. (The production instance was RO...) So the bug,
although very small!, is annoying!
James
On 9/9/20, 6:14 AM, "Amit Kapila" <amit.kapil...@gmail.com> wrote:
CAUTION: This email originated from outside of the organization. Do not
click links or open attachments unless you can confirm the sender and know the
content is safe.
On Tue, Sep 8, 2020 at 11:55 PM Jameson, Hunter 'James'
<hunj...@amazon.com> wrote:
>
> Hi, I ran across a small (but annoying) bug in initializing parallel
BTree scans, which causes the parallel-scan state machine to get confused.
>
>
> To reproduce, you need a query that:
>
>
>
> 1. Executes parallel BTree index scan;
>
> 2. Has an IN-list of size > 1;
>
> 3. Has an additional index filter that makes it impossible to satisfy the
>
> first IN-list condition.
>
>
>
> (We encountered such a query, and therefore the bug, on a production
instance.)
>
>
I think I can understand what you are pointing out here but it would
be great if you can have a reproducible test case because that will
make it apparent and we might want to include that in the regression
tests if possible.
--
With Regards,
Amit Kapila.
