Horton

Thread

Commits

  1. postgres_fdw: Fix interaction of PHVs with child joins.

  1. PlaceHolderVars in pushed down child-join cause error

    Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> — 2018-02-22T12:41:36Z

    Hi,
postgres_fdw isn't expected to push down joins with placeholder vars.
But the check for that in foreign_join_ok() only considers
joinrel->relids. For a child-join relids contains the child relids but
PlaceHolderInfo refers to the top parent's relids. Hence postgres_fdw
tries to push down a child-join with PlaceHolderVars in it and fails
with error "unsupported expression type for deparse: 198". 198 being
T_PlaceHolderVar.

The fix is to use joinrel->top_parent_relids for a child-join.
Attached patch for the same.

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company

  2. Re: PlaceHolderVars in pushed down child-join cause error

    Robert Haas <robertmhaas@gmail.com> — 2018-02-22T15:06:42Z

    On Thu, Feb 22, 2018 at 7:41 AM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
> postgres_fdw isn't expected to push down joins with placeholder vars.
> But the check for that in foreign_join_ok() only considers
> joinrel->relids. For a child-join relids contains the child relids but
> PlaceHolderInfo refers to the top parent's relids. Hence postgres_fdw
> tries to push down a child-join with PlaceHolderVars in it and fails
> with error "unsupported expression type for deparse: 198". 198 being
> T_PlaceHolderVar.
>
> The fix is to use joinrel->top_parent_relids for a child-join.
> Attached patch for the same.

Committed, but I changed the formatting, because as you had it,
pgindent would have mangled it.  While I was at it, I tweaked the
wording of the comment a bit.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

  3. Re: PlaceHolderVars in pushed down child-join cause error

    Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> — 2018-02-26T04:05:45Z

    On Thu, Feb 22, 2018 at 8:36 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Feb 22, 2018 at 7:41 AM, Ashutosh Bapat
> <ashutosh.bapat@enterprisedb.com> wrote:
>> postgres_fdw isn't expected to push down joins with placeholder vars.
>> But the check for that in foreign_join_ok() only considers
>> joinrel->relids. For a child-join relids contains the child relids but
>> PlaceHolderInfo refers to the top parent's relids. Hence postgres_fdw
>> tries to push down a child-join with PlaceHolderVars in it and fails
>> with error "unsupported expression type for deparse: 198". 198 being
>> T_PlaceHolderVar.
>>
>> The fix is to use joinrel->top_parent_relids for a child-join.
>> Attached patch for the same.
>
> Committed, but I changed the formatting, because as you had it,
> pgindent would have mangled it.  While I was at it, I tweaked the
> wording of the comment a bit.

Thanks.


-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company