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

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(at)sss(dot)pgh(dot)pa(dot)us>
发送时间: 2021年4月13日 0:59
收件人: Yulin PEI <ypeiae(at)connect(dot)ust(dot)hk>
抄送: pgsql-hackers(at)lists(dot)postgresql(dot)org <pgsql-hackers(at)lists(dot)postgresql(dot)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(at)connect(dot)ust(dot)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