Message-ID: <b2ac2392-9727-5f76-e890-721ac80c1615@gmail.com>
Date: Thu, 12 Oct 2023 13:00:01 +0300
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Subject: Re: cataloguing NOT NULL constraints
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To: Alvaro Herrera <alvherre@alvh.no-ip.org>,
 Dean Rasheed <dean.a.rasheed@gmail.com>,
 Peter Eisentraut <peter@eisentraut.org>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@lists.postgresql.org
References: <20230825113833.4li4xnii2h4r3mqd@alvherre.pgsql>
From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <20230825113833.4li4xnii2h4r3mqd@alvherre.pgsql>
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Hi Alvaro,

25.08.2023 14:38, Alvaro Herrera wrote:
> I have now pushed this again.  Hopefully it'll stick this time.

I've discovered that that commit added several recursive functions, and
some of them are not protected from stack overflow.

Namely, with "max_locks_per_transaction = 600" and default ulimit -s (8192),
I observe server crashes with the following scripts:
# ATExecSetNotNull()
(n=40000; printf "create table t0 (a int, b int);";
for ((i=1;i<=$n;i++)); do printf "create table t$i() inherits(t$(( $i - 1 ))); "; done;
printf "alter table t0 alter b set not null;" ) | psql >psql.log

# dropconstraint_internal()
(n=20000; printf "create table t0 (a int, b int not null);";
for ((i=1;i<=$n;i++)); do printf "create table t$i() inherits(t$(( $i - 1 ))); "; done;
printf "alter table t0 alter b drop not null;" ) | psql >psql.log

# set_attnotnull()
(n=110000; printf "create table tp (a int, b int, primary key(a, b)) partition by range (a); create table tp0 (a int 
primary key, b int) partition by range (a);";
for ((i=1;i<=$n;i++)); do printf "create table tp$i partition of tp$(( $i - 1 )) for values from ($i) to (1000000) 
partition by range (a);"; done;
printf "alter table tp attach partition tp0 for values from (0) to (1000000);") | psql >psql.log # this takes half an 
hour on my machine

May be you would find appropriate to add check_stack_depth() to these
functions.

(ATAddCheckNNConstraint() is protected because it calls
AddRelationNewConstraints(), which in turn calls StoreRelCheck() ->
CreateConstraintEntry() ->  recordDependencyOnSingleRelExpr() ->
find_expr_references_walker() ->  expression_tree_walker() ->
expression_tree_walker() -> check_stack_depth().)

(There were patches prepared for similar cases [1], but they don't cover new
functions, of course, and I'm not sure how to handle all such instances.)

[1] https://commitfest.postgresql.org/45/4239/

Best regards,
Alexander