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

On Mon, Dec 11, 2017 at 3:54 PM, tushar <tushar(dot)ahuja(at)enterprisedb(dot)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).

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com