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]

    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 <t...@sss.pgh.pa.us>
发送时间: 2021年4月13日 0:59
收件人: Yulin PEI <ype...@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 <ype...@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