RE: libpq debug log

Hi Horiguchi san and Tsunakawa san,

Thank you for you review.

I update patch to v28. In this patch, I removed array.
And I fixed some code according to Horiguchi san and Tsunakawa san review comment.

> From: Tsunakawa, Takayuki/綱川 貴之 <tsunakawa(dot)takay(at)fujitsu(dot)com>
> Sent: Thursday, March 18, 2021 12:38 PM
> I sort of think so to remove the big arrays. But to minimize duplicate code, I
> think the code structure will look like:
>
> fprintf(timestamp, length);
> switch (type)
> {
> case '?':
> pqTraceOutput?(...);
> break;
> case '?':
> /* No message content */
> fprintf("message_type_name");
> break;
> }
>
> void
> pqTraceOutput?(...)
> {
> fprintf("message_type_name");
> print message content;
> }

The code follows above format.
And I changed .sgml documentation;
- Changed order of message length and type
- Removed byte-16 and byte-32 explanation because I removed # output in previous patch.

Output style is following;

```
2021-03-18 08:59:36.141660 < 5 ReadyForQuery I
2021-03-18 08:59:36.141723 > 4 Terminate
2021-03-18 08:59:36.173263 > 155 Query "CREATE TABLESPACE regress_tblspacewith LOCATION '/home/iwata/pgsql/postgres/src/test/regress/testtablespace' WITH (some_nonexistent_parameter = true);"
2021-03-18 08:59:36.174439 < 124 ErrorResponse S "ERROR" V "ERROR" C "22023" M "unrecognized parameter "some_nonexistent_parameter"" F "reloptions.c" L "1456" R "parseRelOptionsInternal" \x00 "Z"
2021-03-18 08:59:36.174483 < 5 ReadyForQuery I
2021-03-18 08:59:36.174545 > 144 Query "CREATE TABLESPACE regress_tblspacewith LOCATION '/home/iwata/pgsql/postgres/src/test/regress/testtablespace' WITH (random_page_cost = 3.0);"
2021-03-18 08:59:36.176155 < 22 CommandComplete "CREATE TABLESPACE"
2021-03-18 08:59:36.176190 < 5 ReadyForQuery I
2021-03-18 08:59:36.176243 > 81 Query "SELECT spcoptions FROM pg_tablespace WHERE spcname = 'regress_tblspacewith';"
2021-03-18 08:59:36.179286 < 35 RowDescription 1 "spcoptions" 1213 5 1009 65535 -1 0
2021-03-18 08:59:36.179326 < 32 DataRow 1 22 '{random_page_cost=3.0}'
2021-03-18 08:59:36.179339 < 13 CommandComplete "SELECT 1"
2021-03-18 08:59:36.179349 < 5 ReadyForQuery I
2021-03-18 08:59:36.179504 > 42 Query "DROP TABLESPACE regress_tblspacewith;"
2021-03-18 08:59:36.180400 < 20 CommandComplete "DROP TABLESPACE"
2021-03-18 08:59:36.180432 < 5 ReadyForQuery I
```

> -----Original Message-----
> From: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
> Sent: Thursday, March 18, 2021 5:30 PM
>
> At Thu, 18 Mar 2021 07:34:36 +0000, "tsunakawa(dot)takay(at)fujitsu(dot)com"
> <tsunakawa(dot)takay(at)fujitsu(dot)com> wrote in
> > From: Iwata, Aya/岩田 彩 <iwata(dot)aya(at)fujitsu(dot)com>
> > > > Yes, precisely, 2 bytes for the double quotes needs to be
> > > > subtracted as
> > > > follows:
> > > >
> > > > len = fprintf(...);
> > > > *cursor += (len - 2);
> > >
> > > Thank you for your advice. I changed pqTraceOutputString set cursor
> > > to fprintf return -2.
> > > And I removed cursor movement from that function.
> >
> > Ouch, not 2 but 3, to include a single whitespace at the beginning.
> >
> > The rest looks good. I hope we're almost at the finish line.
>
> Maybe.

String is end by '\0'. So (len -2) is OK.
However it seems like mistake because fprintf output string and 3 characters.
So I added explanation here and changed (len -2) to (len -3 +1).
I think it is OK because I found similar style in ecpg code.

> > + pqTraceOutputR(const char *message, FILE *f) {
> > + int cursor = 0;
> > +
> > + pqTraceOutputInt32(message, &cursor, f);
> >
> > I don't understand the reason for spliting message and &cursor here.
> >
> > + pqTraceOutputR(const char *message, FILE *f) {
> > + char *p = message;
> > +
> > + pqTraceOutputInt32(&p, f);
> >
> > works well.
>
> Yes, that would also work. But I like the separate cursor + fixed starting
> point here, probably because it's sometimes confusing to see the pointer
> value changed inside functions. (And a pointer itself is an allergy for some
> people, not to mention a pointer to ointer...) Also, libpq uses cursors for
> network I/O buffers. So, I think the patch can be as it is now.

I think pass message and cursor is better. Because it is easy to understand and
The moving cursor style is used when libpq execute protocol message.
So I didn't make this change.

> +/* RowDescription */
> +static void
> +pqTraceOutputT(const char *message, int end, FILE *f) {
> + int cursor = 0;
> + int nfields;
> + int i;
> +
> + nfields = pqTraceOutputInt16(message, &cursor, f);
> +
> + for (i = 0; i < nfields; i++)
> + {
> + pqTraceOutputString(message, &cursor, end, f);
> + pqTraceOutputInt32(message, &cursor, f);
> + pqTraceOutputInt16(message, &cursor, f);
> + pqTraceOutputInt32(message, &cursor, f);
> + pqTraceOutputInt16(message, &cursor, f);
> + pqTraceOutputInt32(message, &cursor, f);
> + pqTraceOutputInt16(message, &cursor, f);
> + }
> +}
>
> I didn't looked closer, but lookong the usage of the variable "end", something's
> wrong in the function.

I removed end from the function.
pqTraceOutputString no longer use message end cursor.

Regards,
Aya Iwata