Message-ID: <gh-pgjdbc-pgjdbc-1136-c514481089@github.com>
From: "maimai3478 (@maimai3478)" <noreply+maimai3478@github.com>
To: "pgjdbc/pgjdbc" <noreply+pgjdbc-pgjdbc@github.com>
Date: Wed, 24 Jul 2019 05:06:14 +0000
Subject: Re: [pgjdbc/pgjdbc] issue #1136: Show SQL text (and/or binds) in SQLException message
In-Reply-To: <gh-pgjdbc-pgjdbc-1136@github.com>
References: <gh-pgjdbc-pgjdbc-1136@github.com>
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> In this case, are more details not possible to be retrieved from the server?

I saw the PostgreSQL codes and it seems me it only generate the error message like "syntax error at or near...". I couldn't find the logic which add more details to error message by the server settings during seeing codes.

That error is generated in during parsing SQL statement.
https://github.com/postgres/postgres/blob/7d81bdc8c0ce838efa248928065e9b2da829f981/src/backend/parser/scan.l#L1145-L1149
```
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
		/* translator: first %s is typically the translation of "syntax error" */
				 errmsg("%s at or near \"%s\"", _(message), loc),
				 lexer_errposition()));
```

ereport() is defined like this.
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/include/utils/elog.h#L120-L142
```
#ifdef HAVE__BUILTIN_CONSTANT_P
#define ereport_domain(elevel, domain, rest)	\
	do { \
		pg_prevent_errno_in_scope(); \
		if (errstart(elevel, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
			errfinish rest; \
		if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
			pg_unreachable(); \
	} while(0)
#else							/* !HAVE__BUILTIN_CONSTANT_P */
#define ereport_domain(elevel, domain, rest)	\
	do { \
		const int elevel_ = (elevel); \
		pg_prevent_errno_in_scope(); \
		if (errstart(elevel_, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
			errfinish rest; \
		if (elevel_ >= ERROR) \
			pg_unreachable(); \
	} while(0)
#endif							/* HAVE__BUILTIN_CONSTANT_P */

#define ereport(elevel, rest)	\
	ereport_domain(elevel, TEXTDOMAIN, rest)
```

errstart() creates an error stack entry and store the given parameters in it.
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/backend/utils/error/elog.c#L360-L365
```
bool
errstart(int elevel, const char *filename, int lineno,
		 const char *funcname, const char *domain)
{
...
	/* Initialize data for this error frame */
	edata = &errordata[errordata_stack_depth];
	MemSet(edata, 0, sizeof(ErrorData));
	edata->elevel = elevel;
	edata->output_to_server = output_to_server;
	edata->output_to_client = output_to_client;
```

The message "syntax error at or near..." is stored in stack entry at errmsg().
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/backend/utils/error/elog.c#L793
```
errmsg(const char *fmt,...)
{
...
	edata->message_id = fmt;
```

errfinish() actually process the error report.
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/backend/utils/error/elog.c#L464
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/backend/utils/error/elog.c#L1712-L1720

Process jump to Postgresmain and finally EmitErrorReport() will send the error message to client.
https://github.com/postgres/postgres/blob/fd7d387e0548fd371c06a91d75bc4632541ccfdd/src/backend/tcop/postgres.c#L4044
```
PostgresMain(int argc, char *argv[],
			 const char *dbname,
			 const char *username)
{
...
		EmitErrorReport();
```

(I'm sorry for not knowing how to cite other repositories source code correctly...)