Horton

Thread

Commits

  1. Remove no-longer-relevant test case.

  2. Fix old bug with coercing the result of a COLLATE expression.

  1. Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Yulin PEI <ypeiae@connect.ust.hk> — 2021-04-12T15:39:38Z

    HI hackers,
    I found it could cause a crash when executing sql statement: `CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10)); ` in postgres 13.2 release.

    The crash happens at view.c:89 and I did some analysis:

```

ColumnDef  *def = makeColumnDef(tle->resname,
                        exprType((Node *) tle->expr),
                        exprTypmod((Node *) tle->expr),
                        exprCollation((Node *) tle->expr));



/*
 * It's possible that the column is of a collatable type but the
 * collation could not be resolved, so double-check.
 */

// Here is the analysis:

//example :  ('4' COLLATE "C")::INT

//exprCollation((Node *) tle->expr) is the oid of collate "COLLATE 'C'" so def->collOid is valid
//exprType((Node *) tle->expr)) is 23 which is the oid of type int4.
//We know that int4 is not collatable by calling type_is_collatable()

if (type_is_collatable(exprType((Node *) tle->expr)))
{
   if (!OidIsValid(def->collOid))
      ereport(ERROR,
            (errcode(ERRCODE_INDETERMINATE_COLLATION),
             errmsg("could not determine which collation to use for view column \"%s\"",
                  def->colname),
             errhint("Use the COLLATE clause to set the collation explicitly.")));
}
else

   // So we are here! int is not collatable and def->collOid is valid.
   Assert(!OidIsValid(def->collOid));

```

I am not sure whether to fix this bug in function DefineVirtualRelation or to fix this bug in parse tree and analyze procedure, so maybe we can discuss.




Best Regard!
Yulin PEI

  2. Re: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Tom Lane <tgl@sss.pgh.pa.us> — 2021-04-12T16:59:43Z

    Yulin PEI <ypeiae@connect.ust.hk> writes:
>     I found it could cause a crash when executing sql statement: `CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10)); ` in postgres 13.2 release.

Nice catch.  I don't think the code in DefineVirtualRelation is wrong:
exprCollation shouldn't report any collation for an expression of a
non-collatable type.  Rather the problem is with an old kluge in
coerce_type(), which will push a type coercion underneath a CollateExpr
... without any mind for the possibility that the coercion result isn't
collatable.  So the right fix is more or less the attached.

			regards, tom lane

  3. 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Yulin PEI <ypeiae@connect.ust.hk> — 2021-04-13T08:27:20Z

        After reading the code and the patch, I think the patch is good. If the type is non-collatable, we do not add a CollateExpr node as a 'parent' node to the coerced node.

________________________________
发件人: Tom Lane <tgl@sss.pgh.pa.us>
发送时间: 2021年4月13日 0:59
收件人: Yulin PEI <ypeiae@connect.ust.hk>
抄送: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
主题: Re: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

Yulin PEI <ypeiae@connect.ust.hk> writes:
>     I found it could cause a crash when executing sql statement: `CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10)); ` in postgres 13.2 release.

Nice catch.  I don't think the code in DefineVirtualRelation is wrong:
exprCollation shouldn't report any collation for an expression of a
non-collatable type.  Rather the problem is with an old kluge in
coerce_type(), which will push a type coercion underneath a CollateExpr
... without any mind for the possibility that the coercion result isn't
collatable.  So the right fix is more or less the attached.

                        regards, tom lane

  4. 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Yulin PEI <ypeiae@connect.ust.hk> — 2021-04-13T09:27:08Z

    I think it is better to add this test case to regress.
________________________________
发件人: Tom Lane <tgl@sss.pgh.pa.us>
发送时间: 2021年4月13日 0:59
收件人: Yulin PEI <ypeiae@connect.ust.hk>
抄送: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
主题: Re: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

Yulin PEI <ypeiae@connect.ust.hk> writes:
>     I found it could cause a crash when executing sql statement: `CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10)); ` in postgres 13.2 release.

Nice catch.  I don't think the code in DefineVirtualRelation is wrong:
exprCollation shouldn't report any collation for an expression of a
non-collatable type.  Rather the problem is with an old kluge in
coerce_type(), which will push a type coercion underneath a CollateExpr
... without any mind for the possibility that the coercion result isn't
collatable.  So the right fix is more or less the attached.

                        regards, tom lane

  5. 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Yulin PEI <ypeiae@connect.ust.hk> — 2021-04-18T16:31:07Z

        After several tests, I found that this patch do not fix the bug well.

    I think we should use the same logic to treat parent CollateExpr and child CollateExpr. In your patch, if the parent node is CollateExpr and the target type is non-collatable,  we coerce CollateExpr->arg. If the child node is CollateExpr and the target type is non-collatable, we just skip.
    Some types can be casted to another type even if  type_is_collatable returns false. Like bytea to int (It depends on the content of the string). If we simply skip,  bytea will never be casted to int even if the content is all digits.

So the attachment is my patch and it works well as far as I tested.



________________________________
发件人: Tom Lane <tgl@sss.pgh.pa.us>
发送时间: 2021年4月13日 0:59
收件人: Yulin PEI <ypeiae@connect.ust.hk>
抄送: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
主题: Re: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

Yulin PEI <ypeiae@connect.ust.hk> writes:
>     I found it could cause a crash when executing sql statement: `CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10)); ` in postgres 13.2 release.

Nice catch.  I don't think the code in DefineVirtualRelation is wrong:
exprCollation shouldn't report any collation for an expression of a
non-collatable type.  Rather the problem is with an old kluge in
coerce_type(), which will push a type coercion underneath a CollateExpr
... without any mind for the possibility that the coercion result isn't
collatable.  So the right fix is more or less the attached.

                        regards, tom lane

  6. Re: 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Tom Lane <tgl@sss.pgh.pa.us> — 2021-04-18T17:46:46Z

    Yulin PEI <ypeiae@connect.ust.hk> writes:
>     After several tests, I found that this patch do not fix the bug well.

What do you think is wrong with it?

> So the attachment is my patch and it works well as far as I tested.

This seems equivalent to the already-committed patch [1] except that
it wastes a makeNode call in the coerce-to-uncollatable-type case.

			regards, tom lane

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=c402b02b9fb53aee2a26876de90a8f95f9a9be92

  7. 回覆: 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Yulin PEI <ypeiae@connect.ust.hk> — 2021-04-19T15:19:29Z

    Consider the SQL statement 'SELECT (('1' COLLATE "C") ||(B'1'));' . Intuitively, the result will be '11' and the result is '11' in pg 13.2 release as well.

The function stack is make_fn_arguments -> coerce_type, which means that the param "Node *node" of function coerce_type could be a CollateExpr Node.
Let's look at your patch:

```
// node is ('1' COLLATE "C")
// targetType is varbit and it is non-collatable
if (IsA(node, CollateExpr) && type_is_collatable(targetTypeId))
{

// we will not reach here.

CollateExpr *coll = (CollateExpr *) node;
CollateExpr *newcoll = makeNode(CollateExpr);

....

// An error will be generated. "failed to find conversion function"

}

```

So I suggest:

```
// node is ('1' COLLATE "C")

if (IsA(node, CollateExpr))
   {
      CollateExpr *coll = (CollateExpr *) node;
      CollateExpr *newcoll = makeNode(CollateExpr);


      //targetType is varbit and it is non-collatable

      if (!type_is_collatable(targetTypeId)) {

         // try to convert '1'(string) to varbit

         // We do not make a new CollateExpr here, but don't forget to coerce coll->arg.

         return coerce_type(pstate, (Node *) coll->arg,
                        inputTypeId, targetTypeId, targetTypeMod,
                        ccontext, cformat, location);
      }
     ...
   }

```






________________________________
寄件者: Tom Lane <tgl@sss.pgh.pa.us>
寄件日期: 2021年4月19日 1:46
收件者: Yulin PEI <ypeiae@connect.ust.hk>
副本: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
主旨: Re: 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

Yulin PEI <ypeiae@connect.ust.hk> writes:
>     After several tests, I found that this patch do not fix the bug well.

What do you think is wrong with it?

> So the attachment is my patch and it works well as far as I tested.

This seems equivalent to the already-committed patch [1] except that
it wastes a makeNode call in the coerce-to-uncollatable-type case.

                        regards, tom lane

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=c402b02b9fb53aee2a26876de90a8f95f9a9be92

  8. Re: 回覆: 回复: Core dump happens when execute sql CREATE VIEW v1(c1) AS (SELECT ('4' COLLATE "C")::INT FROM generate_series(1, 10));

    Tom Lane <tgl@sss.pgh.pa.us> — 2021-04-19T16:47:38Z

    Yulin PEI <ypeiae@connect.ust.hk> writes:
> Let's look at your patch:

> ```
> // node is ('1' COLLATE "C")
> // targetType is varbit and it is non-collatable
> if (IsA(node, CollateExpr) && type_is_collatable(targetTypeId))
> {

> // we will not reach here.

That's not the committed patch, though.  I realized after posting
it that it didn't maintain the same behavior in coerce_type as
coerce_to_target_type.  But the actually-committed fix does, and
as I said, what you're suggesting seems equivalent though a bit
messier.

			regards, tom lane