| From: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
|---|---|
| To: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | PlaceHolderVars in pushed down child-join cause error |
| Date: | 2018-02-22 12:41:36 |
| Message-ID: | CAFjFpRf=J_KPOtw+bhZeURYkbizr8ufSaXg6gPEF6DKpgH-t6g@mail.gmail.com |
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| Lists: | pgsql-hackers |
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
| Attachment | Content-Type | Size |
|---|---|---|
| pgfdw_child_join_phvs.patch | text/x-patch | 3.7 KB |
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