Throws ERROR when statement_mem is set to greater than max_statement_mem

[fairyfar]

Summary

The GPDB's document says that:

statement_mem
Sets the maximum memory limit for a query. Helps avoid out-of-memory errors on a segment host during query processing as a result of setting statement_mem too high.

However, there is no any ERROR when I set statement_mem to greater than max_statement_mem.
So, max_statement_mem loses protection for statement_mem.

Test Case

postgres=# select version();
                                                                                                       version
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 12.12 (Greenplum Database 7.0.0-beta.1+dev.90.g7ac8734891 build dev) on x86_64-pc-linux-gnu, compiled by gcc (GCC) 9.3.1 20200408 (Red Hat 9.3.1-2), 64-bit compiled on Feb 17 2023 10:00:04 Bhuvnesh C.
(1 row)

postgres=# show max_statement_mem;
 max_statement_mem
-------------------
 2000MB
(1 row)

postgres=# show statement_mem;
 statement_mem
---------------
 125MB
(1 row)

-- Set statement_mem > max_statement_mem,
-- but no ERROR reported.
postgres=# set statement_mem = '4000MB';
SET
postgres=# show statement_mem;
 statement_mem
---------------
 4000MB
(1 row)

-- The 'Memory used' of query is 4000MB(4096000kB)
postgres=# explain analyze select 1;
                                     QUERY PLAN
------------------------------------------------------------------------------------
 Result  (cost=0.00..0.00 rows=1 width=1) (actual time=0.002..0.002 rows=1 loops=1)
 Optimizer: Pivotal Optimizer (GPORCA)
 Planning Time: 1.447 ms
   (slice0)    Executor memory: 4K bytes.
 Memory used:  4096000kB
 Execution Time: 0.034 ms
(6 rows)

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[SmartKeyerror]

LTGM. Thanks for your contribution!