Cassandra CQL用法

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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 pytz library. See the timezone option in cqlshrc for specifying a timezone to use.

cython

The performance of cqlsh’s COPY operations can be improved by installing cython. This will compile the python modules that are central to the performance of COPY.

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 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 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


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


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:

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:

cqlsh> SHOW HOST Connected to Prod_Cluster at 192.0.0.1:9042.

SHOW SESSION

Pretty prints a specific tracing session.

Usage: SHOW SESSION


Example usage:

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. | 127.0.0.1 | 0 | 127.0.0.1 Parsing SELECT * FROM system.local; [SharedPool-Worker-1] | 2016-06-14 17:23:13. | 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


Example usage:

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:

CAPTURE ' 
  
    '; 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
. 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:

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:

PAGING ON PAGING OFF PAGING 
  

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:

EXPAND ON EXPAND OFF

LOGIN

Authenticate as a specified Cassandra user for the current session.

Usage:

LOGIN 
  
    [ 
   
     ] 
    
  

EXIT

Ends the current session and terminates the cqlsh process.

Usage:

EXIT QUIT

CLEAR

Clears the console.

Usage:

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:

DESCRIBE CLUSTER DESCRIBE SCHEMA DESCRIBE KEYSPACES DESCRIBE KEYSPACE 
  
    DESCRIBE TABLES DESCRIBE TABLE 
   
     DESCRIBE MATERIALIZED VIEW 
    
      DESCRIBE TYPES DESCRIBE TYPE 
     
       DESCRIBE FUNCTIONS DESCRIBE FUNCTION 
      
        DESCRIBE AGGREGATES DESCRIBE AGGREGATE 
        
       
      
     
    
   
     DESCRIBE INDEX 
    
  

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

The DESCRIBE CLUSTER command prints the cluster name and partitioner:

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:

COPY 
  
    , ...)] TO 
   
     WITH 
    
      [AND 
     
       ...] 
      
     
    
   
  
    [( 
  

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 
 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:

COPY 
  
    , ...)] FROM 
   
     WITH 
    
      [AND 
     
       ...] 
      
     
    
   
  
    [( 
  

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 
 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 .

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_

_


.err

 where 

 is your keyspace and 

 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.