From: Nathan Bossart <nathan@postgresql.org>
Subject: [PATCH v2] attempt multibyte-aware truncation of database names
Date: Wed, 20 Nov 2024 16:30:11 -0600
---
src/backend/utils/init/postinit.c | 76 +++++++++++++++++++++++++++++--
1 file changed, 73 insertions(+), 3 deletions(-)
100.0% src/backend/utils/init/
inline patch 1: src/backend/utils/init/postinit.c (+73/-3 lines) download inline-1.patchdiff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.cindex 5b657a3f13..a594c0d4f3 100644--- a/src/backend/utils/init/postinit.c+++ b/src/backend/utils/init/postinit.c@@ -1003,14 +1003,84 @@ InitPostgres(const char *in_dbname, Oid dboid,
{
HeapTuple tuple;
Form_pg_database dbform;
+ char trunc_dbname[NAMEDATALEN];++ /* truncate to NAMEDATALEN-1 bytes first */+ strncpy(trunc_dbname, in_dbname, NAMEDATALEN - 1);+ trunc_dbname[NAMEDATALEN - 1] = '\0';++ tuple = GetDatabaseTuple(trunc_dbname);+ if (HeapTupleIsValid(tuple))+ strcpy(dbname, trunc_dbname);++ /*+ * If the original name is too long and we see two consecutive bytes+ * with their high bits set at the truncation point, we might have+ * truncated in the middle of a multibyte character. In multibyte+ * encodings, every byte of a multibyte character has its high bit+ * set. So if IS_HIGHBIT_SET is true for both NAMEDATALEN-1 and+ * NAMEDATALEN-2, we know we're in the middle of a multibyte+ * character. We need to try truncating one more byte back to find the+ * start of the next character.+ */+ if (strlen(in_dbname) >= NAMEDATALEN &&+ IS_HIGHBIT_SET(in_dbname[NAMEDATALEN - 1]) &&+ IS_HIGHBIT_SET(in_dbname[NAMEDATALEN - 2]))+ {+ /*+ * Try progressively shorter truncations to find a character+ * boundary. We check at most MAX_MULTIBYTE_CHAR_LEN-1 bytes back.+ */+ for (int i = 1; i < MAX_MULTIBYTE_CHAR_LEN - 1; i++)+ {+ HeapTuple tmp;++ /* truncate one more byte back */+ trunc_dbname[NAMEDATALEN - 1 - i] = '\0';+ tmp = GetDatabaseTuple(trunc_dbname);++ /*+ * If we already had a match then the name is ambiguous and we+ * must fail.+ */+ if (HeapTupleIsValid(tmp))+ {+ if (HeapTupleIsValid(tuple))+ ereport(FATAL,+ (errmsg("ambiguous database name")));+ tuple = tmp;+ strcpy(dbname, trunc_dbname);+ }++ /*+ * If we've hit a byte with high bit clear (an ASCII byte), we+ * know we can't be in the middle of a multibyte character,+ * because all bytes of a multibyte character must have their+ * high bits set. Any following byte must therefore be the+ * start of a new character, so we can stop looking for+ * earlier truncation points.+ */+ if (!IS_HIGHBIT_SET(dbname[NAMEDATALEN - 2 - i]))+ break;+ }+ }- tuple = GetDatabaseTuple(in_dbname);
if (!HeapTupleIsValid(tuple))
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", in_dbname)));
+
dbform = (Form_pg_database) GETSTRUCT(tuple);
dboid = dbform->oid;
++ if (MyProcPort && MyProcPort->database_name &&+ strcmp(MyProcPort->database_name, dbname) != 0)+ {+ pfree(MyProcPort->database_name);+ MyProcPort->database_name = pstrdup(dbname);++ /* XXX: should we fix process title? */+ }
}
else if (!OidIsValid(dboid))
{
@@ -1067,12 +1137,12 @@ InitPostgres(const char *in_dbname, Oid dboid,
datform = (Form_pg_database) GETSTRUCT(tuple);
if (!HeapTupleIsValid(tuple) ||
- (in_dbname && namestrcmp(&datform->datname, in_dbname)))+ (in_dbname && namestrcmp(&datform->datname, dbname)))
{
if (in_dbname)
ereport(FATAL,
(errcode(ERRCODE_UNDEFINED_DATABASE),
- errmsg("database \"%s\" does not exist", in_dbname),+ errmsg("database \"%s\" does not exist", dbname),
errdetail("It seems to have just been dropped or renamed.")));
else
ereport(FATAL,
--
2.34.1
--H+M0G8KNNopj95XV--
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-bugs@postgresql.org
Cc: nathan@postgresql.org
Subject: Re: [PATCH v2] attempt multibyte-aware truncation of database names
In-Reply-To: <no-message-id-25444@localhost>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox