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fix(mysql): only raise group_concat_max_len never lower it

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zipg authored and GitHub committed 2026-09-21 13:36:57 +08:00
1 parent 4dd62b78ec
commit 933c085455
1 file changed
+139 -39
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crates/dbx-drivers/src/db/mysql.rs
+139 -39
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@@ -1305,7 +1305,14 @@ impl MySqlSetupMode {
// configuration with `@@global.group_concat_max_len`), so the built-in
// safety default must not overwrite it.
Self::Standard if !mysql_session_variables_override_group_concat_max_len(url) => {
Some(format!("SET SESSION group_concat_max_len = {MYSQL_GROUP_CONCAT_MAX_LEN}"))
// GREATEST keeps a server that already raises the global limit
// above the built-in floor (for example `SET GLOBAL
// group_concat_max_len = 8388608`) from being silently lowered
// back to the floor by every new session.
Some(format!(
"SET SESSION group_concat_max_len = \
cast(greatest(@@session.group_concat_max_len, {MYSQL_GROUP_CONCAT_MAX_LEN}) as unsigned)"
))
}
Self::Standard | Self::Compatible => None,
}
@@ -1361,14 +1368,25 @@ fn mysql_group_concat_setup_fallback_mode(setup_mode: MySqlSetupMode, error: &st
|| lower.contains("unknown system variable")
|| lower.contains("syntax error")
|| lower.contains("not supported");
// SphinxQL / Manticore reject the built-in `group_concat_max_len` setup with a
// boolean-typed 1064 error. The quoted token after `near` depends on the exact
// statement text, so accept any boolean rejection from SphinxQL that mentions
// the variable or the built-in floor value.
let sphinxql_setup_query_rejected = lower.contains("sphinxql")
&& lower.contains("only 0 and 1 could be used as boolean values")
&& lower.contains(&format!("near '{MYSQL_GROUP_CONCAT_MAX_LEN}'"));
&& (lower.contains("group_concat_max_len") || lower.contains(&format!("near '{MYSQL_GROUP_CONCAT_MAX_LEN}'")));
// Some MySQL gateways omit the variable name and report session-variable
// changes as a forbidden global-variable operation.
let gateway_session_variable_rejected =
lower.contains("error 10192 (hy000)") && lower.contains("set global variables is forbidden");
if (lower.contains("group_concat_max_len") && setup_query_rejected)
// Error echoes of the floor statement always carry the variable name — a
// full-statement echo contains it verbatim, and a token quote like
// `near 'cast(greatest(...)'` spans the rest of the statement after the
// failing token, so the name is still present. Matching on the name alone
// keeps user-supplied `sessionVariables` that merely contain `cast(` from
// triggering a spurious Standard→Compatible retry.
let floor_statement_rejected = lower.contains("group_concat_max_len");
if (floor_statement_rejected && setup_query_rejected)
|| sphinxql_setup_query_rejected
|| gateway_session_variable_rejected
{
@@ -1578,9 +1596,11 @@ fn mysql_setup_queries_for_database_with_mode(
}
queries.push(format!("SET NAMES {charset}"));
// MySQL defaults group_concat_max_len to 1024, which silently truncates
// GROUP_CONCAT results. Skip it for MySQL protocol-compatible databases
// such as old StarRocks versions that reject unknown MySQL variables, and
// for connections that configure the variable themselves.
// GROUP_CONCAT results. Only raise the session value to the built-in floor:
// a server whose global value is already higher keeps its own limit. Skip
// it for MySQL protocol-compatible databases such as old StarRocks versions
// that reject unknown MySQL variables, and for connections that configure
// the variable themselves.
if let Some(query) = setup_mode.group_concat_max_len_query(url) {
queries.push(query);
}
@@ -7989,12 +8009,17 @@ mod tests {
#[test]
fn mysql_cnch_group_concat_syntax_error_retries_without_session_variable() {
let error = "MySQL connection failed: Server error: `ERROR HY000 (1105): unknown error: Error 62 (HY000): Code: 62, e.displayText() = DB::Exception: host = cnch-server-2: Syntax error: failed at position 13 ('group_concat_max_len'): group_concat_max_len = 1048576. Expected one of: Dot, token, Equals SQLSTATE: 42000 (version 21.8.7.1)'";
assert_eq!(
mysql_group_concat_setup_fallback_mode(MySqlSetupMode::Standard, error),
Some(MySqlSetupMode::Compatible)
);
for error in [
"MySQL connection failed: Server error: `ERROR HY000 (1105): unknown error: Error 62 (HY000): Code: 62, e.displayText() = DB::Exception: host = cnch-server-2: Syntax error: failed at position 13 ('group_concat_max_len'): group_concat_max_len = 1048576. Expected one of: Dot, token, Equals SQLSTATE: 42000 (version 21.8.7.1)'",
// Gateways with a reduced parser may quote the expression instead of
// the variable name; the floor statement is still the rejected one.
"MySQL connection failed: Server error: `ERROR HY000 (1105): Syntax error: failed at position 36 ('cast'): cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned). Expected one of: EQUALS'",
] {
assert_eq!(
mysql_group_concat_setup_fallback_mode(MySqlSetupMode::Standard, error),
Some(MySqlSetupMode::Compatible)
);
}
}
#[test]
@@ -8104,12 +8129,18 @@ mod tests {
#[test]
fn mysql_sphinxql_group_concat_boolean_error_retries_without_session_variable() {
let error = "MySQL connection failed: Server error: `ERROR 42000 (1064): sphinxql: only 0 and 1 could be used as boolean values near '1048576'`";
assert_eq!(
mysql_group_concat_setup_fallback_mode(MySqlSetupMode::Standard, error),
Some(MySqlSetupMode::Compatible)
);
for error in [
"MySQL connection failed: Server error: `ERROR 42000 (1064): sphinxql: only 0 and 1 could be used as boolean values near '1048576'`",
// The floor statement now also uses `cast(... as unsigned)`, so
// SphinxQL may quote a different token while reporting the same
// boolean rejection.
"MySQL connection failed: Server error: `ERROR 42000 (1064): sphinxql: only 0 and 1 could be used as boolean values near 'group_concat_max_len'`",
] {
assert_eq!(
mysql_group_concat_setup_fallback_mode(MySqlSetupMode::Standard, error),
Some(MySqlSetupMode::Compatible)
);
}
}
#[test]
@@ -8151,14 +8182,44 @@ mod tests {
fn mysql_setup_queries_select_requested_database_before_session_init() {
let queries = mysql_setup_queries("mysql://root:secret@localhost:3306/app?charset=utf8mb4", &[]);
assert_eq!(queries, vec!["USE `app`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]);
assert_eq!(
queries,
vec![
"USE `app`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
#[test]
fn mysql_group_concat_setup_never_lowers_a_higher_server_limit() {
// A server that already raises `SET GLOBAL group_concat_max_len` above the
// built-in floor (for example 8388608) must keep that value: the setup
// statement raises small session values only.
let queries = mysql_setup_queries("mysql://root:secret@localhost:3306/app?charset=utf8mb4", &[]);
let setup = queries
.iter()
.find(|query| query.contains("group_concat_max_len"))
.expect("group_concat_max_len setup statement");
assert_eq!(
setup,
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
);
}
#[test]
fn mysql_setup_queries_skip_use_when_database_missing() {
let queries = mysql_setup_queries("mysql://root:secret@localhost:3306?charset=utf8mb4", &[]);
assert_eq!(queries, vec!["SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]);
assert_eq!(
queries,
vec![
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
#[test]
@@ -8200,7 +8261,14 @@ mod tests {
fn mysql_setup_queries_decode_database_name_from_url() {
let queries = mysql_setup_queries("mysql://root:secret@localhost:3306/db%2Fname?charset=utf8mb4", &[]);
assert_eq!(queries, vec!["USE `db/name`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]);
assert_eq!(
queries,
vec![
"USE `db/name`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
#[test]
@@ -8209,7 +8277,11 @@ mod tests {
assert_eq!(
queries,
vec!["USE ` analytics `", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE ` analytics `",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8223,7 +8295,11 @@ mod tests {
assert_eq!(
queries,
vec!["USE `app``proxy`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `app``proxy`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8496,7 +8572,11 @@ mod tests {
fn mysql_setup_queries_default_to_utf8mb4() {
assert_eq!(
mysql_setup_queries("mysql://host:3306/db", &[]),
vec!["USE `db`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8504,11 +8584,19 @@ mod tests {
fn mysql_setup_queries_use_safe_custom_charset() {
assert_eq!(
mysql_setup_queries("mysql://host:3306/db?ssl-mode=preferred&charset=gbk", &[]),
vec!["USE `db`", "SET NAMES gbk", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES gbk",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
assert_eq!(
mysql_setup_queries("mysql://host:3306/db?charset=utf8mb4;DROP TABLE users", &[]),
vec!["USE `db`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8521,7 +8609,7 @@ mod tests {
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)",
"SET ob_query_timeout = 30000000"
]
);
@@ -8538,7 +8626,7 @@ mod tests {
"USE `db`",
"SET SESSION query_timeout=60,SESSION sql_mode='STRICT,TRADITIONAL',@trace_id=concat('a,b','c')",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)",
]
);
}
@@ -8547,7 +8635,11 @@ mod tests {
fn mysql_setup_queries_ignore_empty_session_variables() {
assert_eq!(
mysql_setup_queries("mysql://host:9030/db?sessionVariables=%20%2C%20%3B%20", &[]),
vec!["USE `db`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8601,7 +8693,7 @@ mod tests {
"USE `db`",
"SET @group_concat_max_len=2048",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)",
]
);
assert_eq!(
@@ -8610,7 +8702,7 @@ mod tests {
"USE `db`",
"SET @@global.group_concat_max_len=512",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)",
]
);
}
@@ -8623,7 +8715,7 @@ mod tests {
"USE `db`",
"SET time_zone = '+08:00'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
assert_eq!(
@@ -8632,7 +8724,7 @@ mod tests {
"USE `db`",
"SET time_zone = 'Asia/Shanghai'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8645,7 +8737,7 @@ mod tests {
"USE `db`",
"SET time_zone = '+08:00'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
assert_eq!(
@@ -8654,7 +8746,7 @@ mod tests {
"USE `db`",
"SET time_zone = '+00:00'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8667,7 +8759,7 @@ mod tests {
"USE `db`",
"SET time_zone = 'Asia/Shanghai'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
assert_eq!(
@@ -8676,7 +8768,7 @@ mod tests {
"USE `db`",
"SET time_zone = '+08:00'",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = 1048576"
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8685,7 +8777,11 @@ mod tests {
fn mysql_setup_queries_ignore_unsafe_time_zone_values() {
assert_eq!(
mysql_setup_queries("mysql://host:3306/db?time_zone=%2B08%3A00%27%3BDROP%20TABLE%20users", &[]),
vec!["USE `db`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}
@@ -8712,7 +8808,11 @@ mod tests {
fn mysql_setup_queries_omits_catalog_when_absent() {
assert_eq!(
mysql_setup_queries("mysql://host:3306/db?charset=utf8mb4", &[]),
vec!["USE `db`", "SET NAMES utf8mb4", "SET SESSION group_concat_max_len = 1048576"]
vec![
"USE `db`",
"SET NAMES utf8mb4",
"SET SESSION group_concat_max_len = cast(greatest(@@session.group_concat_max_len, 1048576) as unsigned)"
]
);
}