= cqlsh: the CQL shell

`cqlsh` is a command-line interface for interacting with Cassandra using CQL (the Cassandra Query Language). 
It is shipped with every Cassandra package, and can be found in the bin/ directory alongside the cassandra
executable. 
`cqlsh` is implemented with the Python native protocol driver, and connects to the single specified node.

== Compatibility

`cqlsh` is compatible with Python 2.7.

In general, a given version of `cqlsh` is only guaranteed to work with the
version of Cassandra that it was released with. 
In some cases, `cqlsh` may work with older or newer versions of Cassandra, but this is not
officially supported.

== Optional Dependencies

`cqlsh` ships with all essential dependencies. However, there are some
optional dependencies that can be installed to improve the capabilities
of `cqlsh`.

=== pytz

By default, `cqlsh` displays all timestamps with a UTC timezone. 
To support display of timestamps with another timezone, install
the http://pytz.sourceforge.net/[pytz] library. 
See the `timezone` option in xref:cql/tools/cqlsh.adoc#cqlshrc[cqlshrc] for specifying a timezone to
use.

=== cython

The performance of cqlsh's `COPY` operations can be improved by
installing http://cython.org/[cython]. This will compile the python
modules that are central to the performance of `COPY`.

[[cqlshrc]]
== cqlshrc

The `cqlshrc` file holds configuration options for `cqlsh`. 
By default, the file is locagted the user's home directory at `~/.cassandra/cqlsh`, but a
custom location can be specified with the `--cqlshrc` option.

Example config values and documentation can be found in the
`conf/cqlshrc.sample` file of a tarball installation. 
You can also view the latest version of the
https://github.com/apache/cassandra/blob/trunk/conf/cqlshrc.sample[cqlshrc file online].

== Command Line Options

Usage:

`cqlsh [options] [host [port]]`

Options:

`-C` `--color`::
  Force color output
`--no-color`::
  Disable color output
`--browser`::
  Specify the browser to use for displaying cqlsh help. This can be one
  of the https://docs.python.org/2/library/webbrowser.html[supported
  browser names] (e.g. `firefox`) or a browser path followed by `%s`
  (e.g. `/usr/bin/google-chrome-stable %s`).
`--ssl`::
  Use SSL when connecting to Cassandra
`-u` `--user`::
  Username to authenticate against Cassandra with
`-p` `--password`::
  Password to authenticate against Cassandra with, should be used in
  conjunction with `--user`
`-k` `--keyspace`::
  Keyspace to authenticate to, should be used in conjunction with
  `--user`
`-f` `--file`::
  Execute commands from the given file, then exit
`--debug`::
  Print additional debugging information
`--encoding`::
  Specify a non-default encoding for output (defaults to UTF-8)
`--cqlshrc`::
  Specify a non-default location for the `cqlshrc` file
`-e` `--execute`::
  Execute the given statement, then exit
`--connect-timeout`::
  Specify the connection timeout in seconds (defaults to 2s)
`--python /path/to/python`::
  Specify the full path to Python interpreter to override default on
  systems with multiple interpreters installed
`--request-timeout`::
  Specify the request timeout in seconds (defaults to 10s)
`-t` `--tty`::
  Force tty mode (command prompt)

== Special Commands

In addition to supporting regular CQL statements, `cqlsh` also supports a
number of special commands that are not part of CQL. These are detailed
below.

=== `CONSISTENCY`

`Usage`: `CONSISTENCY <consistency level>`

Sets the consistency level for operations to follow. Valid arguments
include:

* `ANY`
* `ONE`
* `TWO`
* `THREE`
* `QUORUM`
* `ALL`
* `LOCAL_QUORUM`
* `LOCAL_ONE`
* `SERIAL`
* `LOCAL_SERIAL`

=== `SERIAL CONSISTENCY`

`Usage`: `SERIAL CONSISTENCY <consistency level>`

Sets the serial consistency level for operations to follow. Valid
arguments include:

* `SERIAL`
* `LOCAL_SERIAL`

The serial consistency level is only used by conditional updates
(`INSERT`, `UPDATE` and `DELETE` with an `IF` condition). For those, the
serial consistency level defines the consistency level of the serial
phase (or “paxos” phase) while the normal consistency level defines the
consistency for the “learn” phase, i.e. what type of reads will be
guaranteed to see the update right away. For example, if a conditional
write has a consistency level of `QUORUM` (and is successful), then a
`QUORUM` read is guaranteed to see that write. But if the regular
consistency level of that write is `ANY`, then only a read with a
consistency level of `SERIAL` is guaranteed to see it (even a read with
consistency `ALL` is not guaranteed to be enough).

=== `SHOW VERSION`

Prints the `cqlsh`, Cassandra, CQL, and native protocol versions in use.
Example:

[source,none]
----
cqlsh> SHOW VERSION
[cqlsh 5.0.1 | Cassandra 3.8 | CQL spec 3.4.2 | Native protocol v4]
----

=== `SHOW HOST`

Prints the IP address and port of the Cassandra node that `cqlsh` is
connected to in addition to the cluster name. Example:

[source,none]
----
cqlsh> SHOW HOST
Connected to Prod_Cluster at 192.0.0.1:9042.
----

=== `SHOW SESSION`

Pretty prints a specific tracing session.

`Usage`: `SHOW SESSION <session id>`

Example usage:

[source,none]
----
cqlsh> SHOW SESSION 95ac6470-327e-11e6-beca-dfb660d92ad8

Tracing session: 95ac6470-327e-11e6-beca-dfb660d92ad8

 activity                                                  | timestamp                  | source    | source_elapsed | client
-----------------------------------------------------------+----------------------------+-----------+----------------+-----------
                                        Execute CQL3 query | 2016-06-14 17:23:13.979000 | 127.0.0.1 |              0 | 127.0.0.1
 Parsing SELECT * FROM system.local; [SharedPool-Worker-1] | 2016-06-14 17:23:13.982000 | 127.0.0.1 |           3843 | 127.0.0.1
...
----

=== `SOURCE`

Reads the contents of a file and executes each line as a CQL statement
or special cqlsh command.

`Usage`: `SOURCE <string filename>`

Example usage:

[source,none]
----
cqlsh> SOURCE '/home/calvinhobbs/commands.cql'
----

=== `CAPTURE`

Begins capturing command output and appending it to a specified file.
Output will not be shown at the console while it is captured.

`Usage`:

[source,none]
----
CAPTURE '<file>';
CAPTURE OFF;
CAPTURE;
----

That is, the path to the file to be appended to must be given inside a
string literal. The path is interpreted relative to the current working
directory. The tilde shorthand notation (`'~/mydir'`) is supported for
referring to `$HOME`.

Only query result output is captured. Errors and output from cqlsh-only
commands will still be shown in the cqlsh session.

To stop capturing output and show it in the cqlsh session again, use
`CAPTURE OFF`.

To inspect the current capture configuration, use `CAPTURE` with no
arguments.

=== `HELP`

Gives information about cqlsh commands. To see available topics, enter
`HELP` without any arguments. To see help on a topic, use
`HELP <topic>`. Also see the `--browser` argument for controlling what
browser is used to display help.

=== `TRACING`

Enables or disables tracing for queries. When tracing is enabled, once a
query completes, a trace of the events during the query will be printed.

`Usage`:

[source,none]
----
TRACING ON
TRACING OFF
----

=== `PAGING`

Enables paging, disables paging, or sets the page size for read queries.
When paging is enabled, only one page of data will be fetched at a time
and a prompt will appear to fetch the next page. Generally, it's a good
idea to leave paging enabled in an interactive session to avoid fetching
and printing large amounts of data at once.

`Usage`:

[source,none]
----
PAGING ON
PAGING OFF
PAGING <page size in rows>
----

=== `EXPAND`

Enables or disables vertical printing of rows. Enabling `EXPAND` is
useful when many columns are fetched, or the contents of a single column
are large.

`Usage`:

[source,none]
----
EXPAND ON
EXPAND OFF
----

=== `LOGIN`

Authenticate as a specified Cassandra user for the current session.

`Usage`:

[source,none]
----
LOGIN <username> [<password>]
----

=== `EXIT`

Ends the current session and terminates the cqlsh process.

`Usage`:

[source,none]
----
EXIT
QUIT
----

=== `CLEAR`

Clears the console.

`Usage`:

[source,none]
----
CLEAR
CLS
----

=== `DESCRIBE`

Prints a description (typically a series of DDL statements) of a schema
element or the cluster. This is useful for dumping all or portions of
the schema.

`Usage`:

[source,none]
----
DESCRIBE CLUSTER
DESCRIBE SCHEMA
DESCRIBE KEYSPACES
DESCRIBE KEYSPACE <keyspace name>
DESCRIBE TABLES
DESCRIBE TABLE <table name>
DESCRIBE INDEX <index name>
DESCRIBE MATERIALIZED VIEW <view name>
DESCRIBE TYPES
DESCRIBE TYPE <type name>
DESCRIBE FUNCTIONS
DESCRIBE FUNCTION <function name>
DESCRIBE AGGREGATES
DESCRIBE AGGREGATE <aggregate function name>
----

In any of the commands, `DESC` may be used in place of `DESCRIBE`.

The `DESCRIBE CLUSTER` command prints the cluster name and partitioner:

[source,none]
----
cqlsh> DESCRIBE CLUSTER

Cluster: Test Cluster
Partitioner: Murmur3Partitioner
----

The `DESCRIBE SCHEMA` command prints the DDL statements needed to
recreate the entire schema. This is especially useful for dumping the
schema in order to clone a cluster or restore from a backup.

=== `COPY TO`

Copies data from a table to a CSV file.

`Usage`:

[source,none]
----
COPY <table name> [(<column>, ...)] TO <file name> WITH <copy option> [AND <copy option> ...]
----

If no columns are specified, all columns from the table will be copied
to the CSV file. A subset of columns to copy may be specified by adding
a comma-separated list of column names surrounded by parenthesis after
the table name.

The `<file name>` should be a string literal (with single quotes)
representing a path to the destination file. This can also the special
value `STDOUT` (without single quotes) to print the CSV to stdout.

See `shared-copy-options` for options that apply to both `COPY TO` and
`COPY FROM`.

==== Options for `COPY TO`

`MAXREQUESTS`::
  The maximum number token ranges to fetch simultaneously. Defaults to
  6.
`PAGESIZE`::
  The number of rows to fetch in a single page. Defaults to 1000.
`PAGETIMEOUT`::
  By default the page timeout is 10 seconds per 1000 entries in the page
  size or 10 seconds if pagesize is smaller.
`BEGINTOKEN`, `ENDTOKEN`::
  Token range to export. Defaults to exporting the full ring.
`MAXOUTPUTSIZE`::
  The maximum size of the output file measured in number of lines;
  beyond this maximum the output file will be split into segments. -1
  means unlimited, and is the default.
`ENCODING`::
  The encoding used for characters. Defaults to `utf8`.

=== `COPY FROM`

Copies data from a CSV file to table.

`Usage`:

[source,none]
----
COPY <table name> [(<column>, ...)] FROM <file name> WITH <copy option> [AND <copy option> ...]
----

If no columns are specified, all columns from the CSV file will be
copied to the table. A subset of columns to copy may be specified by
adding a comma-separated list of column names surrounded by parenthesis
after the table name.

The `<file name>` should be a string literal (with single quotes)
representing a path to the source file. This can also the special value
`STDIN` (without single quotes) to read the CSV data from stdin.

See `shared-copy-options` for options that apply to both `COPY TO` and
`COPY FROM`.

==== Options for `COPY TO`

`INGESTRATE`::
  The maximum number of rows to process per second. Defaults to 100000.
`MAXROWS`::
  The maximum number of rows to import. -1 means unlimited, and is the
  default.
`SKIPROWS`::
  A number of initial rows to skip. Defaults to 0.
`SKIPCOLS`::
  A comma-separated list of column names to ignore. By default, no
  columns are skipped.
`MAXPARSEERRORS`::
  The maximum global number of parsing errors to ignore. -1 means
  unlimited, and is the default.
`MAXINSERTERRORS`::
  The maximum global number of insert errors to ignore. -1 means
  unlimited. The default is 1000.
`ERRFILE` =::
  A file to store all rows that could not be imported, by default this
  is `import_<ks>_<table>.err` where `<ks>` is your keyspace and
  `<table>` is your table name.
`MAXBATCHSIZE`::
  The max number of rows inserted in a single batch. Defaults to 20.
`MINBATCHSIZE`::
  The min number of rows inserted in a single batch. Defaults to 2.
`CHUNKSIZE`::
  The number of rows that are passed to child worker processes from the
  main process at a time. Defaults to 1000.

==== Shared COPY Options

Options that are common to both `COPY TO` and `COPY FROM`.

`NULLVAL`::
  The string placeholder for null values. Defaults to `null`.
`HEADER`::
  For `COPY TO`, controls whether the first line in the CSV output file
  will contain the column names. For COPY FROM, specifies whether the
  first line in the CSV input file contains column names. Defaults to
  `false`.
`DECIMALSEP`::
  The character that is used as the decimal point separator. Defaults to
  `.`.
`THOUSANDSSEP`::
  The character that is used to separate thousands. Defaults to the
  empty string.
`BOOLSTYlE`::
  The string literal format for boolean values. Defaults to
  `True,False`.
`NUMPROCESSES`::
  The number of child worker processes to create for `COPY` tasks.
  Defaults to a max of 4 for `COPY FROM` and 16 for `COPY TO`. However,
  at most (num_cores - 1) processes will be created.
`MAXATTEMPTS`::
  The maximum number of failed attempts to fetch a range of data (when
  using `COPY TO`) or insert a chunk of data (when using `COPY FROM`)
  before giving up. Defaults to 5.
`REPORTFREQUENCY`::
  How often status updates are refreshed, in seconds. Defaults to 0.25.
`RATEFILE`::
  An optional file to output rate statistics to. By default, statistics
  are not output to a file.