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Date: Fri, 25 Jul 2025 08:20:26 -0700
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Subject: Re: Upper / lower case keys in JSON objects
To: Mark <nvpostgres@gmail.com>, pgsql-general@postgresql.org
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From: Adrian Klaver <adrian.klaver@aklaver.com>
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On 7/25/25 05:26, Mark wrote:
> Hi all
> 
> Apologies for any unexpected protocol exceptions, I do not post to 
> mailing lists very often
> 
> I have been trying to work with JSON objects and noticed I could not get 
> the function json_to_record to produce results, unless I had the key 
> values in lower case, through testing what works.
> 
> I completed a search, but could not find any pointer (except for some 
> front end comments on labels being all upper or all lower case)
> 
> Could anybody comment if the postgres standard is to have key labels in 
> lower case?

Yes and no. It comes down to this:

https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS

"Quoting an identifier also makes it case-sensitive, whereas unquoted 
names are always folded to lower case. For example, the identifiers FOO, 
foo, and "foo" are considered the same by PostgreSQL, but "Foo" and 
"FOO" are different from these three and each other. (The folding of 
unquoted names to lower case in PostgreSQL is incompatible with the SQL 
standard, which says that unquoted names should be folded to upper case. 
Thus, foo should be equivalent to "FOO" not "foo" according to the 
standard. If you want to write portable applications you are advised to 
always quote a particular name or never quote it.)"

So on the Postgres(SQL) side 'as x(seclvl int, firbal text, firlvl text
, thilvl text, fourlvl int)' if you want to match the mixed case keys 
coming from the JSON object you need to double quote the field names.

The yes is that Postgres by default folds identifiers to lower case, but 
no that does not mean you have to use lower case by default for the JSON 
keys.

> 
> Many thanks for any help you can provide
> 
> Mark
> 
> query:
> select * from json_to_record('{"secLvl": 13, "firBal": "somethi", 
> "firLvl": "C", "thiLvl": "A", "fourLvl": 2}'::json) as x(seclvl int, 
> firbal text, firlvl text
> , thilvl text, fourlvl int);
> 
> result:
> seclvl | firbal | firlvl | thilvl | fourlvl
> --------+--------+--------+--------+---------
>         |        |        |        |
> (1 row)
> 
> 
> query:
> select * from json_to_record('{"seclvl": 13, "firbal": "somethi", 
> "firlvl": "C", "thilvl": "A", "fourlvl": 2}'::json) as x(seclvl int, 
> firbal text, firlvl text
> , thilvl text, fourlvl int);
> 
> result:
> seclvl | firbal  | firlvl | thilvl | fourlvl
> --------+---------+--------+--------+---------
>      13 | somethi | C      | A      |       2
> (1 row)
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com