Allow db.schema.table patterns, but complain about random garbage.

psql, pg_dump, and pg_amcheck share code to process object name
patterns like 'foo*.bar*' to match all tables with names starting in
'bar' that are in schemas starting with 'foo'. Before v14, any number
of extra name parts were silently ignored, so a command line '\d
foo.bar.baz.bletch.quux' was interpreted as '\d bletch.quux'.  In v14,
as a result of commit 2c8726c, we
instead treated this as a request for table quux in a schema named
'foo.bar.baz.bletch'. That caused problems for people like Justin
Pryzby who were accustomed to copying strings of the form
db.schema.table from messages generated by PostgreSQL itself and using
them as arguments to \d.

Accordingly, revise things so that if an object name pattern contains
more parts than we're expecting, we throw an error, unless there's
exactly one extra part and it matches the current database name.
That way, thisdb.myschema.mytable is accepted as meaning just
myschema.mytable, but otherdb.myschema.mytable is an error, and so
is some.random.garbage.myschema.mytable.

Mark Dilger, per report from Justin Pryzby and discussion among
various people.

Discussion: https://www.postgresql.org/message-id/20211013165426.GD27491%40telsasoft.com

Author: robertmhaas

doc/src/sgml/ref/psql-ref.sgml

@@ -3641,14 +3641,27 @@ select 1\; select 2\; select 3;
   </para>
 
   <para>
-   A pattern that contains a dot (<literal>.</literal>) is interpreted as a schema
+   A relation pattern that contains a dot (<literal>.</literal>) is interpreted as a schema
    name pattern followed by an object name pattern.  For example,
    <literal>\dt foo*.*bar*</literal> displays all tables whose table name
    includes <literal>bar</literal> that are in schemas whose schema name
    starts with <literal>foo</literal>.  When no dot appears, then the pattern
    matches only objects that are visible in the current schema search path.
    Again, a dot within double quotes loses its special meaning and is matched
-   literally.
+   literally.  A relation pattern that contains two dots (<literal>.</literal>)
+   is interpreted as a database name followed by a schema name pattern followed
+   by an object name pattern.  The database name portion will not be treated as
+   a pattern and must match the name of the currently connected database, else
+   an error will be raised.
+  </para>
+
+  <para>
+   A schema pattern that contains a dot (<literal>.</literal>) is interpreted
+   as a database name followed by a schema name pattern.  For example,
+   <literal>\dn mydb.*foo*</literal> displays all schemas whose schema name
+   includes <literal>foo</literal>.  The database name portion will not be
+   treated as a pattern and must match the name of the currently connected
+   database, else an error will be raised.
   </para>
 
   <para>

src/bin/pg_amcheck/pg_amcheck.c

@@ -1308,10 +1308,17 @@ static void
 append_database_pattern(PatternInfoArray *pia, const char *pattern, int encoding)
 {
 	PQExpBufferData buf;
+	int			dotcnt;
 	PatternInfo *info = extend_pattern_info_array(pia);
 
 	initPQExpBuffer(&buf);
-	patternToSQLRegex(encoding, NULL, NULL, &buf, pattern, false);
+	patternToSQLRegex(encoding, NULL, NULL, &buf, pattern, false, false,
+					  &dotcnt);
+	if (dotcnt > 0)
+	{
+		pg_log_error("improper qualified name (too many dotted names): %s", pattern);
+		exit(2);
+	}
 	info->pattern = pattern;
 	info->db_regex = pstrdup(buf.data);
 
@@ -1332,12 +1339,19 @@ append_schema_pattern(PatternInfoArray *pia, const char *pattern, int encoding)
 {
 	PQExpBufferData dbbuf;
 	PQExpBufferData nspbuf;
+	int			dotcnt;
 	PatternInfo *info = extend_pattern_info_array(pia);
 
 	initPQExpBuffer(&dbbuf);
 	initPQExpBuffer(&nspbuf);
 
-	patternToSQLRegex(encoding, NULL, &dbbuf, &nspbuf, pattern, false);
+	patternToSQLRegex(encoding, NULL, &dbbuf, &nspbuf, pattern, false, false,
+					  &dotcnt);
+	if (dotcnt > 1)
+	{
+		pg_log_error("improper qualified name (too many dotted names): %s", pattern);
+		exit(2);
+	}
 	info->pattern = pattern;
 	if (dbbuf.data[0])
 	{
@@ -1369,13 +1383,20 @@ append_relation_pattern_helper(PatternInfoArray *pia, const char *pattern,
 	PQExpBufferData dbbuf;
 	PQExpBufferData nspbuf;
 	PQExpBufferData relbuf;
+	int			dotcnt;
 	PatternInfo *info = extend_pattern_info_array(pia);
 
 	initPQExpBuffer(&dbbuf);
 	initPQExpBuffer(&nspbuf);
 	initPQExpBuffer(&relbuf);
 
-	patternToSQLRegex(encoding, &dbbuf, &nspbuf, &relbuf, pattern, false);
+	patternToSQLRegex(encoding, &dbbuf, &nspbuf, &relbuf, pattern, false,
+					  false, &dotcnt);
+	if (dotcnt > 2)
+	{
+		pg_log_error("improper relation name (too many dotted names): %s", pattern);
+		exit(2);
+	}
 	info->pattern = pattern;
 	if (dbbuf.data[0])
 	{

src/bin/pg_amcheck/t/002_nonesuch.pl

@@ -147,6 +147,100 @@
 	[qr/pg_amcheck: error: no heap tables to check matching "\."/],
 	'checking table pattern "."');
 
+# Check that a multipart database name is rejected
+$node->command_checks_all(
+	[ 'pg_amcheck', '-d', 'localhost.postgres' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): localhost\.postgres/
+	],
+	'multipart database patterns are rejected'
+);
+
+# Check that a three-part schema name is rejected
+$node->command_checks_all(
+	[ 'pg_amcheck', '-s', 'localhost.postgres.pg_catalog' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): localhost\.postgres\.pg_catalog/
+	],
+	'three part schema patterns are rejected'
+);
+
+# Check that a four-part table name is rejected
+$node->command_checks_all(
+	[ 'pg_amcheck', '-t', 'localhost.postgres.pg_catalog.pg_class' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper relation name \(too many dotted names\): localhost\.postgres\.pg_catalog\.pg_class/
+	],
+	'four part table patterns are rejected'
+);
+
+# Check that too many dotted names still draws an error under --no-strict-names
+# That flag means that it is ok for the object to be missing, not that it is ok
+# for the object name to be ungrammatical
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-t', 'this.is.a.really.long.dotted.string' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper relation name \(too many dotted names\): this\.is\.a\.really\.long\.dotted\.string/
+	],
+	'ungrammatical table names still draw errors under --no-strict-names'
+);
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-s', 'postgres.long.dotted.string' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): postgres\.long\.dotted\.string/
+	],
+	'ungrammatical schema names still draw errors under --no-strict-names'
+);
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-d', 'postgres.long.dotted.string' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): postgres\.long\.dotted\.string/
+	],
+	'ungrammatical database names still draw errors under --no-strict-names'
+);
+
+# Likewise for exclusion patterns
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-T', 'a.b.c.d' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper relation name \(too many dotted names\): a\.b\.c\.d/
+	],
+	'ungrammatical table exclusions still draw errors under --no-strict-names'
+);
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-S', 'a.b.c' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): a\.b\.c/
+	],
+	'ungrammatical schema exclusions still draw errors under --no-strict-names'
+);
+$node->command_checks_all(
+	[ 'pg_amcheck', '--no-strict-names', '-D', 'a.b' ],
+	2,
+	[qr/^$/],
+	[
+		qr/pg_amcheck: error: improper qualified name \(too many dotted names\): a\.b/
+	],
+	'ungrammatical database exclusions still draw errors under --no-strict-names'
+);
+
+
 #########################################
 # Test checking non-existent databases, schemas, tables, and indexes
 
@@ -165,9 +259,7 @@
 		'-d',         'no*such*database',
 		'-r',         'none.none',
 		'-r',         'none.none.none',
-		'-r',         'this.is.a.really.long.dotted.string',
 		'-r',         'postgres.none.none',
-		'-r',         'postgres.long.dotted.string',
 		'-r',         'postgres.pg_catalog.none',
 		'-r',         'postgres.none.pg_class',
 		'-t',         'postgres.pg_catalog.pg_class',          # This exists
@@ -186,15 +278,12 @@
 		qr/pg_amcheck: warning: no connectable databases to check matching "no\*such\*database"/,
 		qr/pg_amcheck: warning: no relations to check matching "none\.none"/,
 		qr/pg_amcheck: warning: no connectable databases to check matching "none\.none\.none"/,
-		qr/pg_amcheck: warning: no connectable databases to check matching "this\.is\.a\.really\.long\.dotted\.string"/,
 		qr/pg_amcheck: warning: no relations to check matching "postgres\.none\.none"/,
-		qr/pg_amcheck: warning: no relations to check matching "postgres\.long\.dotted\.string"/,
 		qr/pg_amcheck: warning: no relations to check matching "postgres\.pg_catalog\.none"/,
 		qr/pg_amcheck: warning: no relations to check matching "postgres\.none\.pg_class"/,
 		qr/pg_amcheck: warning: no connectable databases to check matching "no_such_database"/,
 		qr/pg_amcheck: warning: no connectable databases to check matching "no\*such\*database"/,
 		qr/pg_amcheck: warning: no connectable databases to check matching "none\.none\.none"/,
-		qr/pg_amcheck: warning: no connectable databases to check matching "this\.is\.a\.really\.long\.dotted\.string"/,
 	],
 	'many unmatched patterns and one matched pattern under --no-strict-names'
 );

src/bin/pg_dump/pg_dump.c

@@ -178,6 +178,9 @@ static void expand_table_name_patterns(Archive *fout,
 									   SimpleStringList *patterns,
 									   SimpleOidList *oids,
 									   bool strict_names);
+static void prohibit_crossdb_refs(PGconn *conn, const char *dbname,
+								  const char *pattern);
+
 static NamespaceInfo *findNamespace(Oid nsoid);
 static void dumpTableData(Archive *fout, const TableDataInfo *tdinfo);
 static void refreshMatViewData(Archive *fout, const TableDataInfo *tdinfo);
@@ -1315,10 +1318,21 @@ expand_schema_name_patterns(Archive *fout,
 
 	for (cell = patterns->head; cell; cell = cell->next)
 	{
+		PQExpBufferData	dbbuf;
+		int		dotcnt;
+
 		appendPQExpBufferStr(query,
 							 "SELECT oid FROM pg_catalog.pg_namespace n\n");
+		initPQExpBuffer(&dbbuf);
 		processSQLNamePattern(GetConnection(fout), query, cell->val, false,
-							  false, NULL, "n.nspname", NULL, NULL);
+							  false, NULL, "n.nspname", NULL, NULL, &dbbuf,
+							  &dotcnt);
+		if (dotcnt > 1)
+			pg_fatal("improper qualified name (too many dotted names): %s",
+					 cell->val);
+		else if (dotcnt == 1)
+			prohibit_crossdb_refs(GetConnection(fout), dbbuf.data, cell->val);
+		termPQExpBuffer(&dbbuf);
 
 		res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 		if (strict_names && PQntuples(res) == 0)
@@ -1362,10 +1376,16 @@ expand_extension_name_patterns(Archive *fout,
 	 */
 	for (cell = patterns->head; cell; cell = cell->next)
 	{
+		int		dotcnt;
+
 		appendPQExpBufferStr(query,
 							 "SELECT oid FROM pg_catalog.pg_extension e\n");
 		processSQLNamePattern(GetConnection(fout), query, cell->val, false,
-							  false, NULL, "e.extname", NULL, NULL);
+							  false, NULL, "e.extname", NULL, NULL, NULL,
+							  &dotcnt);
+		if (dotcnt > 0)
+			pg_fatal("improper qualified name (too many dotted names): %s",
+					 cell->val);
 
 		res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 		if (strict_names && PQntuples(res) == 0)
@@ -1409,10 +1429,16 @@ expand_foreign_server_name_patterns(Archive *fout,
 
 	for (cell = patterns->head; cell; cell = cell->next)
 	{
+		int		dotcnt;
+
 		appendPQExpBufferStr(query,
 							 "SELECT oid FROM pg_catalog.pg_foreign_server s\n");
 		processSQLNamePattern(GetConnection(fout), query, cell->val, false,
-							  false, NULL, "s.srvname", NULL, NULL);
+							  false, NULL, "s.srvname", NULL, NULL, NULL,
+							  &dotcnt);
+		if (dotcnt > 0)
+			pg_fatal("improper qualified name (too many dotted names): %s",
+					 cell->val);
 
 		res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 		if (PQntuples(res) == 0)
@@ -1455,6 +1481,9 @@ expand_table_name_patterns(Archive *fout,
 
 	for (cell = patterns->head; cell; cell = cell->next)
 	{
+		PQExpBufferData	dbbuf;
+		int		dotcnt;
+
 		/*
 		 * Query must remain ABSOLUTELY devoid of unqualified names.  This
 		 * would be unnecessary given a pg_table_is_visible() variant taking a
@@ -1470,9 +1499,17 @@ expand_table_name_patterns(Archive *fout,
 						  RELKIND_RELATION, RELKIND_SEQUENCE, RELKIND_VIEW,
 						  RELKIND_MATVIEW, RELKIND_FOREIGN_TABLE,
 						  RELKIND_PARTITIONED_TABLE);
+		initPQExpBuffer(&dbbuf);
 		processSQLNamePattern(GetConnection(fout), query, cell->val, true,
 							  false, "n.nspname", "c.relname", NULL,
-							  "pg_catalog.pg_table_is_visible(c.oid)");
+							  "pg_catalog.pg_table_is_visible(c.oid)", &dbbuf,
+							  &dotcnt);
+		if (dotcnt > 2)
+			pg_fatal("improper relation name (too many dotted names): %s",
+					 cell->val);
+		else if (dotcnt == 2)
+			prohibit_crossdb_refs(GetConnection(fout), dbbuf.data, cell->val);
+		termPQExpBuffer(&dbbuf);
 
 		ExecuteSqlStatement(fout, "RESET search_path");
 		res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
@@ -1493,6 +1530,26 @@ expand_table_name_patterns(Archive *fout,
 	destroyPQExpBuffer(query);
 }
 
+/*
+ * Verifies that the connected database name matches the given database name,
+ * and if not, dies with an error about the given pattern.
+ *
+ * The 'dbname' argument should be a literal name parsed from 'pattern'.
+ */
+static void
+prohibit_crossdb_refs(PGconn *conn, const char *dbname, const char *pattern)
+{
+	const char *db;
+
+	db = PQdb(conn);
+	if (db == NULL)
+		pg_fatal("You are currently not connected to a database.");
+
+	if (strcmp(db, dbname) != 0)
+		pg_fatal("cross-database references are not implemented: %s",
+				 pattern);
+}
+
 /*
  * checkExtensionMembership
  *		Determine whether object is an extension member, and if so,

src/bin/pg_dump/pg_dumpall.c

@@ -1269,10 +1269,21 @@ expand_dbname_patterns(PGconn *conn,
 
 	for (SimpleStringListCell *cell = patterns->head; cell; cell = cell->next)
 	{
+		int		dotcnt;
+
 		appendPQExpBufferStr(query,
 							 "SELECT datname FROM pg_catalog.pg_database n\n");
 		processSQLNamePattern(conn, query, cell->val, false,
-							  false, NULL, "datname", NULL, NULL);
+							  false, NULL, "datname", NULL, NULL, NULL,
+							  &dotcnt);
+
+		if (dotcnt > 0)
+		{
+			pg_log_error("improper qualified name (too many dotted names): %s",
+						 cell->val);
+			PQfinish(conn);
+			exit_nicely(1);
+		}
 
 		res = executeQuery(conn, query->data);
 		for (int i = 0; i < PQntuples(res); i++)