Re: After dropping the rule - Not able to insert / server crash (onetime ONLY)

On Mon, Dec 11, 2017 at 3:54 PM, tushar <tushar.ahuja@enterprisedb.com> wrote:

Hi,

While testing something , I found that even after rule has dropped  not able to insert data  and in an another scenario , there is a Crash/

Please refer this scenario's -

1) Rows not inserted after dropping the RULE

postgres=# create table e(n int);
CREATE TABLE
postgres=# create rule e1 as on insert to e do instead nothing;
CREATE RULE
postgres=# create function e11(n int) returns int as $$ begin insert into e values(10); return 1; end; $$ language 'plpgsql';
CREATE FUNCTION
postgres=# select e11(1);
 e11
-----
   1
(1 row)

postgres=# select e11(1);
 e11
-----
   1
(1 row)

postgres=# select * from e;  => Expected , due to  the RULE enforced
 n
---
(0 rows)


postgres=# drop rule e1 on e;  ==>Drop the rule
DROP RULE

postgres=# select e11(1);  =>again try to insert into table
 e11
-----
   1
(1 row)

postgres=# select * from e;  =>This time , value should be inserted but still showing 0 row.
 n
---
(0 rows)

2)Server crash (one time)

postgres=# create table en(n int);
CREATE TABLE
postgres=# create function en1(n int) returns int as $$ begin insert into en values(10); return 1; end; $$ language 'plpgsql';
CREATE FUNCTION
postgres=#
postgres=# select en1(1);
 en1
-----
   1
(1 row)

postgres=# select * from en;
 n
----
 10
(1 row)

postgres=# create rule en11 as on insert to en do instead nothing;
CREATE RULE
postgres=# select en1(1);
ostgres=# select en1(1);
TRAP: FailedAssertion("!(!stmt->mod_stmt)", File: "pl_exec.c", Line: 3721)
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.

I have looked into this crash, seems like below assert in exec_stmt_execsql is not correct

case SPI_OK_REWRITTEN:

Assert(!stmt->mod_stmt);

In this issue first time execution of select en1(1); statement, stmt->mod_stmt is set to true for the insert query inside the function. Then before next execution we have created the rule "create rule en11 as on insert to en do instead nothing;".  Because of this nothing will be executed and output will be SPI_OK_REWRITTEN.  But we are asserting that stmt->mod_stmt should be false (which were set to true in first execution).