Re: making the backend's json parser work in frontend code

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Mark Dilger <mark.dilger@enterprisedb.com>

Cc: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, David Steele <david@pgmasters.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>

Date: 2020-01-27T13:30:27Z

Lists: pgsql-hackers

On Sun, Jan 26, 2020 at 9:05 PM Mark Dilger
<mark.dilger@enterprisedb.com> wrote:
> Ok, the tests pass.  Here are those two patches again, both regenerated with a fresh invocation of ‘git format-patch’.

Regarding 0006:

+#ifndef FRONTEND
 #include "miscadmin.h"
-#include "utils/jsonapi.h"
+#endif

I suggest

#ifdef FRONTEND
#define check_stack_depth()
#else
#include "miscadmin.h"
#endif

- lex->token_terminator = s + pg_mblen(s);
+ lex->token_terminator = s +
pg_wchar_table[lex->input_encoding].mblen((const unsigned char *) s);

Can we use pq_encoding_mblen() here? Regardless, it doesn't seem great
to add more direct references to pg_wchar_table. I think we should
avoid that.

+ return JSON_BAD_PARSER_STATE;

I don't like this, either. I'm thinking about adding some
variable-argument macros that either elog() in backend code or else
pg_log_fatal() and exit(1) in frontend code. There are some existing
precedents already (e.g. rmtree.c, pgfnames.c) which could perhaps be
generalized. I think I'll start a new thread about that.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

Add jsonapi.c to Mkvcbuild.pm's @pgcommonallfiles.
- 006b9dcad419 13.0 landed
Move jsonapi.c and jsonapi.h to src/common.
- beb4699091e9 13.0 landed
Move some code from jsonapi.c to jsonfuncs.c.
- 73ce2a03f30b 13.0 landed
Adjust pg_parse_json() so that it does not directly ereport().
- 1f3a021730be 13.0 landed
Remove jsonapi.c's lex_accept().
- 530609aa4263 13.0 landed
Split JSON lexer/parser from 'json' data type support.
- 11b5e3e35d39 13.0 landed
Rationalize code placement between wchar.c, encnames.c, and mbutils.c.
- 5afaa2e42655 13.0 landed
Move wchar.c and encnames.c to src/common/.
- e6afa8918c46 13.0 landed
Update header comments for wchar.c and encnames.c.
- 3d4cb5d6c180 13.0 landed
Make StringInfo available to frontend code.
- 26aaf97b683d 13.0 cited
Use SASLprep to normalize passwords for SCRAM authentication.
- 60f11b87a234 10.0 cited