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From: jian he <jian.universality@gmail.com>
Date: Tue, 21 Jan 2025 17:29:30 +0800
Message-ID: <CACJufxEA-Q2hatN_BLcNrgfo8-4-m102gDdwVp0NTbuM2zyeDA@mail.gmail.com>
Subject: Re: Non-text mode for pg_dumpall
To: Mahendra Singh Thalor <mahi6run@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Guillaume Lelarge <guillaume@lelarge.info>, 
	Nathan Bossart <nathandbossart@gmail.com>, Magnus Hagander <magnus@hagander.net>, 
	Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew@dunslane.net>, 
	PostgreSQL-development <pgsql-hackers@postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>
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Precedence: bulk

hi.

+ printfPQExpBuffer(query,
+ "SELECT substring ( "
+ " '%s' , "
+ " '%s' ) ", str, ptrn);
+   result = executeQuery(conn, query->data);
+ if (PQresultStatus(result) == PGRES_TUPLES_OK)
+ {
+ if (PQntuples(result) == 1)
+ {
+ const char *outstr;
+
+ outstr = PQgetvalue(result, 0, 0);
i think here you should use PQgetisnull(result, 0, 0)
?


example: pg_dumpall and pg_restore:
$BIN10/pg_dumpall --verbose --format=custom --file=x12.dump
$BIN10/pg_restore --verbose --dbname=src10 x12.dump

some log message for the above command:
pg_restore: found dbname as : "template1" and db_oid:1 in map.dat file
while restoring
pg_restore: found dbname as : "s1" and db_oid:17960 in map.dat file
while restoring
pg_restore: found dbname as : "src10" and db_oid:5 in map.dat file
while restoring
pg_restore: found total 3 database names in map.dat file
pg_restore: needs to restore 3 databases out of 3 databases
pg_restore: restoring dump of pg_dumpall without -C option, there
might be multiple databases in directory.
pg_restore: restoring database "template1"
pg_restore: connecting to database for restore
pg_restore: implied data-only restore
pg_restore: restoring database "s1"
pg_restore: connecting to database for restore
pg_restore: processing data for table "public.t"
pg_restore: while PROCESSING TOC:
pg_restore: from TOC entry 3376; 0 17961 TABLE DATA t jian
pg_restore: error: could not execute query: ERROR:  relation
"public.t" does not exist
Command was: COPY public.t (a) FROM stdin;


1. message: "pg_restore: implied data-only restore"
Normally pg_dump and  pg_restore will dump the schema and the data,
then when we are connecting to the same database with pg_restore,
there will be lots of schema elements already exists ERROR.
but the above command case, pg_restore only restores the content/data
not schema, that's why there is very little error happening.
so here pg_restore not restore schema seems not ok?


2. pg_dumpall with non-text mode, we don't have \connect command in
file global.dat or map.dat
I have database "s1" with table "public.t".
if I create a table src10.public.t (database.schema.table)  with column a.
then pg_restore will restore content of s1.public.t (database s1) to
src10.public.t (database src10).

in ConnectDatabase(Archive *AHX,
                const ConnParams *cparams,
                bool isReconnect)
i added
    if (cparams->dbname)
        fprintf(stderr, "pg_backup_db.c:%d %s called connecting to %s
now\n", __LINE__, __func__, cparams->dbname);
to confirm that we are connecting the same database "src10", while
dumping all the contents in x12.dump.