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postgres_fdw: Fix oversights in fetch_attstats().

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The query to get attribute statistics from a remote server applied the
"C" collation to a column of type name without checking the server's
version.  Since the name type was made collatable in Postgres 12, this
could break attribute statistics import if the server was older.  Fix by
casting the column value to text before collating it if the server is
older.

Also, fix a typo in the if-test in the same function.

Oversights in commit 28972b6fc; the former was reported by Fujii Masao.

Reported-by: Fujii Masao <masao.fujii@gmail.com>
Author: Etsuro Fujita <etsuro.fujita@gmail.com>
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwGvA_3q7Wg7GXQkuugGZj3%3DkxDRjDsKgVvK1uwAxHTopQ%40mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Etsuro Fujita
2026-09-18 17:45:00 +09:00
parent 59bc960fa1
commit bea01b825c
1 changed files with 22 additions and 7 deletions
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29
contrib/postgres_fdw/postgres_fdw.c
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@@ -6003,12 +6003,23 @@ fetch_attstats(PGconn *conn, int server_version_num,
StringInfoData sql;
PGresult *res;
/* The caller guarantees the remote server is v9.1 or later. */
/*
* The caller guarantees the remote server is v9.1, which supported
* COLLATE "C", or later
*/
Assert(server_version_num >= 90100);
initStringInfo(&sql);
/* Type name is collatable since Postgres 12 */
if (server_version_num >= 120000)
appendStringInfoString(&sql,
"SELECT DISTINCT ON (attname COLLATE \"C\") attname,");
else
appendStringInfoString(&sql,
"SELECT DISTINCT ON (attname::text COLLATE \"C\") attname,");
appendStringInfoString(&sql,
"SELECT DISTINCT ON (attname COLLATE \"C\") attname,"
" null_frac,"
" avg_width,"
" n_distinct,"
@@ -6018,7 +6029,7 @@ fetch_attstats(PGconn *conn, int server_version_num,
" correlation,");
/* Elements stats are supported since Postgres 9.2 */
if (server_version_num >= 92000)
if (server_version_num >= 90200)
appendStringInfoString(&sql,
" most_common_elems,"
" most_common_elem_freqs,"
@@ -6049,11 +6060,15 @@ fetch_attstats(PGconn *conn, int server_version_num,
column_list);
/*
* inherited and COLLATE are supported since Postgres 9.0 and 9.1,
* respectively.
* Type name is collatable since Postgres 12 (inherited is supported
* since Postgres 9.0)
*/
appendStringInfoString(&sql,
" ORDER BY attname COLLATE \"C\", inherited DESC");
if (server_version_num >= 120000)
appendStringInfoString(&sql,
" ORDER BY attname COLLATE \"C\", inherited DESC");
else
appendStringInfoString(&sql,
" ORDER BY attname::text COLLATE \"C\", inherited DESC");
res = pgfdw_exec_query(conn, sql.data, NULL);
if (PQresultStatus(res) != PGRES_TUPLES_OK)