Re: UPDATE on Domain Array that is based on a composite key crashes - Mailing list pgsql-hackers

[ please do not quote the entire thread when replying ]

Zhihong Yu <zyu@yugabyte.com> writes:
> Here is the patch.

This patch seems quite misguided to me.  The proximate cause of
the crash is that we're arriving at ExecEvalFieldStoreDeForm with
*op->resnull and *op->resvalue both zero, which is a completely
invalid situation for a pass-by-reference datatype; so something
upstream of this messed up.  Even if there were an argument for
acting as though that were a valid NULL value, this patch fails to
do so; that'd require setting all the output fieldstore.nulls[]
entries to true, which you didn't.

Moreover, experiment quickly shows that the problem only shows up with
an array of domain over composite, not an array of plain composite.
The proposed patch doesn't seem to have anything to do with that
observation.

After some digging around, I see where the issue actually is:
the expression tree we're dealing with looks like

                 {SUBSCRIPTINGREF
                 :refexpr
                    {VAR
                    }
                 :refassgnexpr
                    {COERCETODOMAIN
                    :arg
                       {FIELDSTORE
                       :arg
                          {CASETESTEXPR
                          }
                       }
                    }
                 }

The array element we intend to replace has to be passed down to
the CaseTestExpr, but that isn't happening.  That's because
isAssignmentIndirectionExpr fails to recognize a tree like
this, so ExecInitSubscriptingRef doesn't realize it needs to
arrange for that.

I believe the attached is a correct fix.

                        regards, tom lane