Thread: BUG #16770: PostgreSQL software V11 does not eliminate this recheck_on_update option?

The following bug has been logged on the website:

Bug reference:      16770
Logged by:          yanliang lei
Email address:      leiyanliang@highgo.com
PostgreSQL version: 11.10
Operating system:   CentOS7.6
Description:

in pg11 create index statement have recheck_on_update option，but this option
do not exist in the documents
in the pg11.1 releasenote，recheck_on_update optimization is
disabled(https://www.postgresql.org/docs/11/release-11-1.html) 
and in the pg11 create index
document(https://www.postgresql.org/docs/current/sql-createindex.html#SQL-CREATEINDEX-STORAGE-PARAMETERS)，there
is nothing about recheck_on_update 

but the create index sql with recheck_on_update='on' execute succuessfully,
why? PostgreSQL software V11 does not  eliminate this recheck_on_update
option?

postgres=# CREATE INDEX idx1_t_tab_x ON t_tab_x(upper(c4)) WITH
(recheck_on_update = on) ;
CREATE INDEX
postgres=# \d+ t_tab_x
                                         Table "public.t_tab_x"
 Column |         Type          | Collation | Nullable | Default | Storage
| Stats target | Description 
--------+-----------------------+-----------+----------+---------+----------+--------------+-------------
 c1     | integer               |           | not null |         | plain
|              | 
 c2     | integer               |           | not null |         | plain
|              | 
 c3     | integer               |           |          |         | plain
|              | 
 c4     | character varying(10) |           |          |         | extended
|              | 
Indexes:
    "t_tab_x_pkey" PRIMARY KEY, btree (c1, c2) INCLUDE (c3)
    "idx1_t_tab_x" btree (upper(c4::text)) WITH (recheck_on_update='on')

postgres=# \d+ idx_t_tab_x
Did not find any relation named "idx_t_tab_x".
postgres=# \d+ idx1_t_tab_x
                   Index "public.idx1_t_tab_x"
 Column | Type | Key? |   Definition    | Storage  | Stats target 
--------+------+------+-----------------+----------+--------------
 upper  | text | yes  | upper(c4::text) | extended | 
btree, for table "public.t_tab_x"
Options: recheck_on_update=on

postgres=# 
postgres=# select version();
                                                 version
                             
----------------------------------------------------------------------------------------------------------
 PostgreSQL 11.10 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-39), 64-bit
(1 row)

postgres=#

Hello

It's related to commits:
https://git.postgresql.org/pg/commitdiff/c203d6cf81b4d7e43edb2b75ec1b741ba48e04e0
https://git.postgresql.org/pg/commitdiff/5d28c9bd73e29890cccd3f6b188b86f81031f671
https://git.postgresql.org/pg/commitdiff/1c53c4dec3985512f7f2f53c9d76a5295cd0a2dd

Feature was reverted in master. Remains present in pg11, but nonfunctional and undocumented to avoid an ABI break for
codetouching relcache entries.
 

regards, Sergei