Обсуждение: PlaceHolderVars in pushed down child-join cause error
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
Вложения
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
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