tidb_load_binding_timeout cannot rightly init the default value

[hawkingrei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

As the log shows, The duration is 4.8µs. it is not expected. and the user doesn't update this value.

{"level":"WARN","time":"2025/06/18 21:54:59.873 +00:00","caller":"binding_cache.go:164","message":"failed to load binding from storage","category":"sql-bind","sqlDigest":"ef7f1cf1ec0c2e0891e40d26dbe1b95d9c517683663b8d0e035ab160126c4c63","error":"load bindings from storage timeout","errorVerbose":"load bindings from storage timeout
github.com/pingcap/tidb/pkg/bindinfo.(*globalBindingHandle).LoadBindingsFromStorage
\t/mnt/tidb/sql/pkg/bindinfo/global_handle.go:713
github.com/pingcap/tidb/pkg/bindinfo.(*fuzzyBindingCache).loadFromStore
\t/mnt/tidb/sql/pkg/bindinfo/binding_cache.go:162
github.com/pingcap/tidb/pkg/bindinfo.(*fuzzyBindingCache).FuzzyMatchingBinding
\t/mnt/tidb/sql/pkg/bindinfo/binding_cache.go:106
github.com/pingcap/tidb/pkg/bindinfo.(*globalBindingHandle).MatchGlobalBinding
\t/mnt/tidb/sql/pkg/bindinfo/global_handle.go:473
github.com/pingcap/tidb/pkg/bindinfo.matchSQLBinding
\t/mnt/tidb/sql/pkg/bindinfo/binding_match.go:89
github.com/pingcap/tidb/pkg/bindinfo.MatchSQLBinding
\t/mnt/tidb/sql/pkg/bindinfo/binding_match.go:53
github.com/pingcap/tidb/pkg/planner.Optimize
\t/mnt/tidb/sql/pkg/planner/optimize.go:220
github.com/pingcap/tidb/pkg/executor.(*Compiler).Compile
\t/mnt/tidb/sql/pkg/executor/compiler.go:104
github.com/pingcap/tidb/pkg/session.(*session).ExecuteStmt
\t/mnt/tidb/sql/pkg/session/session.go:2086
github.com/pingcap/tidb/pkg/server.(*TiDBContext).ExecuteStmt
\t/mnt/tidb/sql/pkg/server/driver_tidb.go:294
github.com/pingcap/tidb/pkg/server.(*clientConn).handleStmt
\t/mnt/tidb/sql/pkg/server/conn.go:2030
github.com/pingcap/tidb/pkg/server.(*clientConn).handleQuery
\t/mnt/tidb/sql/pkg/server/conn.go:1783
github.com/pingcap/tidb/pkg/server.(*clientConn).dispatch
\t/mnt/tidb/sql/pkg/server/conn.go:1357
github.com/pingcap/tidb/pkg/server.(*clientConn).Run
\t/mnt/tidb/sql/pkg/server/conn.go:1127
github.com/pingcap/tidb/pkg/server.(*Server).onConn
\t/mnt/tidb/sql/pkg/server/server.go:740
runtime.goexit
\t/usr/local/go/src/runtime/asm_amd64.s:1650","duration":"4.8µs"}

so I add a assert into the problem place and CI report the panic at here. This indicates that there indeed is an issue here.

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)