schrddl

Randomized concurrent DDL/DML correctness testing framework for TiDB.

schrddl continuously generates and executes mixed workloads (DDL + DML), then checks whether TiDB’s behavior matches the expected in-memory/metadata model (and, in parallel mode, uses TiDB DDL job ordering to replay operations locally).

What This Repo Contains

• main.go: CLI entry and flags.
• ddl/: DDL/DML execution engine (parallel/serial/txn modes, metadata, validators).
• framework/: unified SQL correctness framework (optional engine).
• sqlgenerator/: probabilistic SQL generator (functional DSL + hooks).

Requirements

• Go 1.24+ (see go.mod)
• A TiDB instance reachable via MySQL protocol
• A dedicated database/schema for testing (the tool creates/drops/renames tables, indexes, schemas, etc.)

Warning: do not run this against a production cluster.

Build

go build -o schrddl

Run (Requires TiDB)

./schrddl \
  -addr "127.0.0.1:4000" \
  -db "test" \
  -mode "parallel" \
  -concurrency 20 \
  -tables 1 \
  -time 2h

Engines

schrddl supports two engines:

• -engine ddl (default): legacy randomized concurrent DDL/DML engine in ddl/.
• -engine framework: unified SQL correctness framework in framework/ (optional oracles such as NoREC/TLP/EET/CERT).

Framework-specific flags:

• -aqs: enable Approximate Query Synthesis
• -cert: enable CERT
• -tlp: enable TLP
• -eet: enable EET
• -pprof-addr: start pprof HTTP server (e.g. 127.0.0.1:6060)

Note: -global-sort-uri only applies to -engine ddl.

Common Flags

• -addr: TiDB address in host:port (default 127.0.0.1:4000)
• -db: database/schema name (default test)
• -mode: serial or parallel
• -concurrency: number of concurrent workers (default 20)
• -tables: initial tables to create per worker (default 1, but currently clamped to a minimum of 2)
• -time: total running time (default 2h)
• -mysql-compatible: disable TiDB-only checks/features where applicable
• -output: log file path (empty means stdout)

Advanced Flags

• -txn: enable transactional DML executor
• -rc-txn: use read-committed isolation (also sets TiDB global transaction_isolation)
• -prepare: use prepared statements for DML
• -check-ddl-extra-timeout: extra timeout for background “DDL queue drained” checks
• -global-sort-uri: enable dist task and set tidb_cloud_storage_uri (for features that require global sort storage)

Notes / Behavior

• Connection DSN is currently fixed as root:@tcp(<addr>)/<db> (no user/password flags).
• The runner sets some TiDB globals (e.g. time zone, max_execution_time; and dist-task globals when -global-sort-uri is set).
• The process has a hard exit loop after the configured duration (see main.go), so expect os.Exit(0) shortly after -time.

Development

Run unit tests:

go test ./...

Generate example SQL (prints to stdout):

go test -v -run TestReadMeExample ./sqlgenerator/

Docker

docker build -t hub.pingcap.net/qa/schrddl-master .