Meta Commands

In tsql, any command that begins with an unquoted backslash (‘\’) is a tsql meta-command that is processed by tsql itself.

In the current implementation, there are meta commands as follows:

default> \?


General
  \copyright    show Apache License 2.0
  \version      show Tajo version
  \?            show help
  \? [COMMAND]  show help of a given command
  \help         alias of \?
  \q            quit tsql


Informational
  \l           list databases
  \c           show current database
  \c [DBNAME]  connect to new database
  \d           list tables
  \d [TBNAME]  describe table
  \df          list functions
  \df NAME     describe function


Tool
  \!           execute a linux shell command
  \dfs         execute a dfs command
  \admin       execute Tajo admin command


Variables
  \set [[NAME] [VALUE]  set session variable or list session variables
  \unset NAME           unset session variable


Documentations
  tsql guide        http://tajo.apache.org/docs/current/tsql.html
  Query language    http://tajo.apache.org/docs/current/sql_language.html
  Functions         http://tajo.apache.org/docs/current/functions.html
  Backup & restore  http://tajo.apache.org/docs/current/backup_and_restore.html
  Configuration     http://tajo.apache.org/docs/current/configuration.html

Basic usages

\l command shows a list of all databases as follows:

default> \l
default
tpch
work1
default>

\d command shows a list of tables in the current database as follows:

default> \d
customer
lineitem
nation
orders
part
partsupp
region
supplier

\d [table name] command also shows a table description as follows:

default> \d orders

table name: orders
table path: hdfs:/xxx/xxx/tpch/orders
store type: CSV
number of rows: 0
volume (bytes): 172.0 MB
schema:
o_orderkey      INT8
o_custkey       INT8
o_orderstatus   TEXT
o_totalprice    FLOAT8
o_orderdate     TEXT
o_orderpriority TEXT
o_clerk TEXT
o_shippriority  INT4
o_comment       TEXT

The prompt default> indicates the current database. Basically, all SQL statements and meta commands work in the current database. Also, you can change the current database with \c command.

default> \c work1
You are now connected to database "test" as user "hyunsik".
work1>

\df command shows a list of all built-in functions as follows:

default> \df
 Name            | Result type     | Argument types        | Description                                   | Type
-----------------+-----------------+-----------------------+-----------------------------------------------+-----------
 abs             | INT4            | INT4                  | Absolute value                                | GENERAL
 abs             | INT8            | INT8                  | Absolute value                                | GENERAL
 abs             | FLOAT4          | FLOAT4                | Absolute value                                | GENERAL
 abs             | FLOAT8          | FLOAT8                | Absolute value                                | GENERAL
 acos            | FLOAT8          | FLOAT4                | Inverse cosine.                               | GENERAL
 acos            | FLOAT8          | FLOAT8                | Inverse cosine.                               | GENERAL
 utc_usec_to     | INT8            | TEXT,INT8             | Extract field from time                       | GENERAL
 utc_usec_to     | INT8            | TEXT,INT8,INT4        | Extract field from time                       | GENERAL

(181) rows

For Reference, many details have been omitted in order to present a clear picture of the process.

\df [function name] command also shows a function description as follows:

default> \df round;
 Name            | Result type     | Argument types        | Description                                   | Type
-----------------+-----------------+-----------------------+-----------------------------------------------+-----------
 round           | INT8            | FLOAT4                | Round to nearest integer.                     | GENERAL
 round           | INT8            | FLOAT8                | Round to nearest integer.                     | GENERAL
 round           | INT8            | INT4                  | Round to nearest integer.                     | GENERAL
 round           | INT8            | INT8                  | Round to nearest integer.                     | GENERAL
 round           | FLOAT8          | FLOAT8,INT4           | Round to s decimalN places.                   | GENERAL
 round           | FLOAT8          | INT8,INT4             | Round to s decimalN places.                   | GENERAL

(6) rows

Function:    INT8 round(float4)
Description: Round to nearest integer.
Example:
> SELECT round(42.4)
42

Function:    FLOAT8 round(float8,int4)
Description: Round to s decimalN places.
Example:
> SELECT round(42.4382, 2)
42.44