vtexplain is a command line tool which provides information on how Vitess plans to execute a particular query.

It can be used to validate queries for compatibility with Vitess.

For a user guide that describes how to use the vtexplain tool to explain how Vitess executes a particular SQL statement, see Analyzing a SQL statement.

## Limitations

### The VSchema must use a keyspace name.

VTExplain requires a keyspace name for each keyspace in an input VSchema:
```
"keyspace_name": {
    "_comment": "Keyspace definition goes here."
}
```

If no keyspace name is present, VTExplain will return the following error:
```
ERROR: initVtgateExecutor: json: cannot unmarshal bool into Go value of type map[string]json.RawMessage
```

Usage:
  vtexplain [flags]

Examples:
Explain how Vitess will execute the query `SELECT * FROM users` using the VSchema contained in `vschemas.json` and the database schema `schema.sql`:

```
vtexplain --vschema-file vschema.json --schema-file schema.sql --sql "SELECT * FROM users"
```

Explain how the example will execute on 128 shards using Row-based replication:

```
vtexplain -- -shards 128 --vschema-file vschema.json --schema-file schema.sql --replication-mode "ROW" --output-mode text --sql "INSERT INTO users (user_id, name) VALUES(1, 'john')"
```


Flags:
      --alsologtostderr                                             log to standard error as well as files
      --batch-interval duration                                     Interval between logical time slots. (default 10ms)
      --config-file string                                          Full path of the config file (with extension) to use. If set, --config-path, --config-type, and --config-name are ignored.
      --config-file-not-found-handling ConfigFileNotFoundHandling   Behavior when a config file is not found. (Options: error, exit, ignore, warn) (default warn)
      --config-name string                                          Name of the config file (without extension) to search for. (default "vtconfig")
      --config-path strings                                         Paths to search for config files in. (default [/tmp])
      --config-persistence-min-interval duration                    minimum interval between persisting dynamic config changes back to disk (if no change has occurred, nothing is done). (default 1s)
      --config-type string                                          Config file type (omit to infer config type from file extension).
      --dbname string                                               Optional database target to override normal routing
      --default_tablet_type topodatapb.TabletType                   The default tablet type to set for queries, when one is not explicitly selected. (default PRIMARY)
      --execution-mode string                                       The execution mode to simulate -- must be set to multi, legacy-autocommit, or twopc (default "multi")
  -h, --help                                                        help for vtexplain
      --keep_logs duration                                          keep logs for this long (using ctime) (zero to keep forever)
      --keep_logs_by_mtime duration                                 keep logs for this long (using mtime) (zero to keep forever)
      --ks-shard-map string                                         JSON map of keyspace name -> shard name -> ShardReference object. The inner map is the same as the output of FindAllShardsInKeyspace
      --ks-shard-map-file string                                    File containing json blob of keyspace name -> shard name -> ShardReference object
      --log_backtrace_at traceLocations                             when logging hits line file:N, emit a stack trace
      --log_dir string                                              If non-empty, write log files in this directory
      --log_err_stacks                                              log stack traces for errors
      --log_rotate_max_size uint                                    size in bytes at which logs are rotated (glog.MaxSize) (default 1887436800)
      --logtostderr                                                 log to standard error instead of files
      --mysql_server_version string                                 MySQL server version to advertise. (default "8.0.40-Vitess")
      --normalize                                                   Whether to enable vtgate normalization
      --output-mode string                                          Output in human-friendly text or json (default "text")
      --planner-version string                                      Sets the default planner to use. Valid values are: Gen4, Gen4Greedy, Gen4Left2Right
      --pprof strings                                               enable profiling
      --pprof-http                                                  enable pprof http endpoints
      --purge_logs_interval duration                                how often try to remove old logs (default 1h0m0s)
      --replication-mode string                                     The replication mode to simulate -- must be set to either ROW or STATEMENT (default "ROW")
      --schema string                                               The SQL table schema
      --schema-file string                                          Identifies the file that contains the SQL table schema
      --security_policy string                                      the name of a registered security policy to use for controlling access to URLs - empty means allow all for anyone (built-in policies: deny-all, read-only)
      --shards int                                                  Number of shards per keyspace. Passing --ks-shard-map/--ks-shard-map-file causes this flag to be ignored. (default 2)
      --sql string                                                  A list of semicolon-delimited SQL commands to analyze
      --sql-file string                                             Identifies the file that contains the SQL commands to analyze
      --sql-max-length-errors int                                   truncate queries in error logs to the given length (default unlimited)
      --sql-max-length-ui int                                       truncate queries in debug UIs to the given length (default 512) (default 512)
      --stderrthreshold severityFlag                                logs at or above this threshold go to stderr (default 1)
      --v Level                                                     log level for V logs
  -v, --version                                                     print binary version
      --vmodule vModuleFlag                                         comma-separated list of pattern=N settings for file-filtered logging
      --vschema string                                              Identifies the VTGate routing schema
      --vschema-file string                                         Identifies the VTGate routing schema file