Re: path toward faster partition pruning

Hello Amit,

Thanks for the updated patches

On Wed, Oct 25, 2017 at 1:07 PM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2017/10/25 15:47, Amit Langote wrote:
>> On 2017/10/24 1:38, Beena Emerson wrote:
>>> I had noticed this and also that this crash:
>>>
>>> tprt PARTITION BY RANGE(Col1)
>>> tprt_1 FOR VALUES FROM (1) TO (50001) PARTITION BY RANGE(Col1)
>>> tprt_11 FOR VALUES FROM (1) TO (10000),
>>> tprt_1d DEFAULT
>>> tprt_2 FOR VALUES FROM (50001) TO (100001)
>>>
>>> EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 BETWEEN 20000 AND 70000;
>>> server closed the connection unexpectedly
>>> This probably means the server terminated abnormally
>>> before or while processing the request.
>>> The connection to the server was lost. Attempting reset: Failed.
>>> !>
>>
>> ...and this (crash) were due to bugs in the 0005 patch.
>
> [ .... ]
>
>> Should be fixed in the attached updated version.
>
> Oops, not quite. The crash that Beena reported wasn't fixed (or rather
> reintroduced by some unrelated change after once confirming it was fixed).
>
> Really fixed this time.
>

The crashes are fixed. However, handling of DEFAULT partition in
various queries is not proper.

Case 1: In this case default should be selected.
DROP TABLE tprt;
CREATE TABLE tprt (col1 int, col2 int) PARTITION BY range(col1);
CREATE TABLE tprt_1 PARTITION OF tprt FOR VALUES FROM (1) TO (50001)
PARTITION BY list(col1);
CREATE TABLE tprt_11 PARTITION OF tprt_1 FOR VALUES IN (20000, 25000);
CREATE TABLE tprt_12 PARTITION OF tprt_1 FOR VALUES IN (50000, 35000);
CREATE TABLE tprt_13 PARTITION OF tprt_1 FOR VALUES IN (10000);
CREATE TABLE tprt_1d PARTITION OF tprt_1 DEFAULT;

postgres=# EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 < 10000;
QUERY PLAN
--------------------------
Result
One-Time Filter: false
(2 rows)

Case 2: In this case DEFAULT need not be selected.

DROP TABLE tprt;
CREATE TABLE tprt (col1 int, col2 int) PARTITION BY range(col1);
CREATE TABLE tprt_1 PARTITION OF tprt FOR VALUES FROM (1) TO (50001)
PARTITION BY range(col1);
CREATE TABLE tprt_11 PARTITION OF tprt_1 FOR VALUES FROM (1) TO (10000);
CREATE TABLE tprt_12 PARTITION OF tprt_1 FOR VALUES FROM (10000) TO (20000);
CREATE TABLE tprt_13 PARTITION OF tprt_1 FOR VALUES FROM (20000) TO (30000);
CREATE TABLE tprt_1d PARTITION OF tprt_1 DEFAULT;
INSERT INTO tprt SELECT generate_series(1,50000), generate_series(1,50000);

postgres=# EXPLAIN (COSTS OFF) SELECT * FROM tprt WHERE col1 < 10000;
QUERY PLAN
--------------------------------
Append
-> Seq Scan on tprt_11
Filter: (col1 < 10000)
-> Seq Scan on tprt_1d
Filter: (col1 < 10000)
(5 rows)

--

Beena Emerson

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