Overview

Basic Features

  • Connect to the database: By default, only the local server can be connected. To connect to a remote database, you must configure the server. For details, see Database Usage > Connecting to a Database > Using gsql to Connect to a Database > Remotely Connecting to a Database in the Developer Guide.

    NOTE: If gsql is used to connect to a database, the connection timeout period will be 5 minutes. If the database has not correctly set up a connection and authenticated the identity of the client within this period, gsql will time out and exit. To resolve this problem, see Troubleshooting.

  • Run SQL statements: Interactively entered SQL statements and specified SQL statements in a file can be run.

  • Run meta-commands: Meta-commands help the administrator view database object information, query cache information, format SQL output, and connect to a new database. For details about meta-commands, see Meta-Command Reference.

Advanced Features

Table 1 lists the advanced features of gsql.

Table 1 Advanced features of gsql

Feature Name

Description

Variable

gsql provides a variable feature that is similar to the shell command of Linux. The following \set meta-command of gsql can be used to set a variable:

\set varname value

To delete the variables set by the \set command, run the following command:

\unset varname
NOTE:
  • A variable is a simple name-value pair. The value can be any characters in any length.
  • Variable names must consist of case-sensitive letters (including non-Latin letters), digits, and underscores (_).
  • If the \set varname meta-command (without the second parameter) is used, the variable is set without a value specified.
  • If the \set meta-command without parameters is used, values of all variables are displayed.

For details about variable examples and descriptions, see Variables.

SQL substitution

Common SQL statements can be set to variables using the variable feature of gsql to simplify operations.

For details about examples and descriptions about SQL substitution, see SQL substitution.

Customized prompt

Prompts of gsql can be customized. Prompts can be modified by changing the reserved three variables of gsql: PROMPT1, PROMPT2, and PROMPT3.

These variables can be set to customized values or the values predefined by gsql. For details, see Prompt.

Historical client operation records

gsql can record historical client operations. This function is enabled by specifying the -r parameter when a client is connected. The number of historical records can be set using the \set command. For example, \set HISTSIZE 50 indicates that the number of historical records is set to 50. \set HISTSIZE 0 indicates that the operation history is not recorded.

NOTE:
  • The default number of historical records is 32. The maximum number of historical records is 500. If interactively entered SQL commands contain Chinese characters, only the UTF-8 encoding environment is supported.
  • For security reasons, the records containing sensitive words, such as PASSWORD and IDENTIFIED, are regarded sensitive and not recorded in historical information. This indicates that you cannot view these records in command output histories.
  • Variables

    To set a variable, run the \set meta-command of gsql. For example, to set variable foo to bar, run the following command:

    openGauss=# \set foo bar
    

    To reference the value of a variable, add a colon (:) before the variable. For example, to view the value of variable foo, run the following command:

    openGauss=# \echo :foo
    bar
    

    The variable reference method is suitable for regular SQL statements and meta-commands.

    gsql pre-defines some special variables and plans the values of these variables. To ensure compatibility with later versions, do not use these variables for other purposes. For details about special variables, see Table 2.

    NOTE:

    • All the special variables consist of upper-case letters, digits, and underscores (_).
    • To view the default value of a special variable, run the \echo :varname meta-command, for example, \echo :DBNAME.

    Table 2 Settings of special variables

    Variable

    Setting Method

    Description

    DBNAME

    \set DBNAME dbname

    Name of the connected database. This variable is set again when a database is connected.

    ECHO

    \set ECHO all | queries
    • If this variable is set to all, only the query information is displayed. This has the same effect as specifying the -a parameter when gsql is used to connect to a database.
    • If this variable is set to queries, the command line and query information are displayed. This has the same effect as specifying the -e parameter when gsql is used to connect to a database.

    ECHO_HIDDEN

    \set ECHO_HIDDEN  on | off | noexec

    When a meta-command (such as \dg) is used to query database information, the value of this variable determines the query behavior.

    • If this variable is set to on, the query statements that are called by the meta-command are displayed, and then the query result is displayed. This has the same effect as specifying the -E parameter when gsql is used to connect to a database.
    • If this variable is set to off, only the query result is displayed.
    • If this variable is set to noexec, only the query information is displayed, and the query is not run.

    ENCODING

    \set ENCODING   encoding

    Character set encoding of the current client.

    FETCH_COUNT

    \set FETCH_COUNT variable
    • If the value is an integer greater than 0, for example, n, n lines will be selected from the result set to the cache and displayed on the screen when the SELECT statement is run.
    • If this variable is not set or set to a value less than or equal to 0, all results are selected at a time to the cache when the SELECT statement is run.
    NOTE:

    A proper variable value helps reduce the memory usage. The recommended value range is from 100 to 1000.

    HISTCONTROL

    \set HISTCONTROL  ignorespace | ignoredups | ignoreboth | none
    • ignorespace: A line started with a space is not written to the historical record.
    • ignoredups: A line that exists in the historical record is not written to the historical record.
    • ignoreboth, none, or other values: All the lines read in interaction mode are saved in the historical record.
      NOTE:

      none indicates that HISTCONTROL is not set.

    HISTFILE

    \set HISTFILE filename

    Specifies the file for storing historical records. The default value is ~/.bash_history.

    HISTSIZE

    \set HISTSIZE size

    Specifies the number of commands to store in the command history. The default value is 500.

    HOST

    \set HOST hostname

    Specifies the name of a connected host.

    IGNOREEOF

    \set IGNOREEOF variable
    • If this variable is set to a number, for example, 10, the first nine EOF characters (generally Ctrl+C) entered in gsql are neglected and the gsql program exits when the tenth Ctrl+C is entered.
    • If this variable is set to a non-numeric value, the default value is 10.
    • If this variable is deleted, gsql exits when an EOF is entered.

    LASTOID

    \set LASTOID oid

    Specifies the last OID, which is the value returned by an INSERT or lo_import command. This variable is valid only before the output of the next SQL statement is displayed.

    ON_ERROR_ROLLBACK

    \set  ON_ERROR_ROLLBACK  on | interactive | off
    • If the value is on, an error that may occur in a statement in a transaction block is ignored and the transaction continues.
    • If the value is interactive, the error is ignored only in an interactive session.
    • If the value is off (default value), the error triggers the rollback of the transaction block. In on_error_rollback-on mode, a SAVEPOINT is set before each statement of a transaction block, and an error triggers the rollback of the transaction block.

    ON_ERROR_STOP

    \set ON_ERROR_STOP on | off
    • on: specifies that the execution stops if an error occurs. In interactive mode, gsql returns the output of executed commands immediately.
    • off (default value): specifies that an error, if occurring during the execution, is ignored, and the execution continues.

    PORT

    \set PORT port

    Specifies the port number of a connected database.

    USER

    \set USER username

    Specifies the database user you are currently connected as.

    VERBOSITY

    \set VERBOSITY   terse | default | verbose

    This variable can be set to terse, default, or verbose to control redundant lines of error reports.

    • terse: Only critical and major error texts and text locations are returned (which is generally suitable for single-line error information).
    • default: Critical and major error texts and text locations, error details, and error messages (possibly involving multiple lines) are all returned.
    • verbose: All error information is returned.
  • SQL substitution

    gsql, like a parameter of a meta-command, provides a key feature that enables you to substitute a standard SQL statement for a gsql variable. gsql also provides a new alias or identifier for the variable. To replace the value of a variable using the SQL substitution method, add a colon (:) before the variable. For example:

    openGauss=# \set foo 'HR.areaS'
    openGauss=# select * from :foo;
     area_id |       area_name        
    ---------+------------------------
           4 | Middle East and Africa
           3 | Asia
           1 | Europe
           2 | Americas
    (4 rows)
    

    The above command queries the HR.areaS table.

    NOTICE: The value of the variable is copied literally, so it can even contain unbalanced quotation marks or backslash commands. Therefore, the input content must be meaningful.

  • Prompt

    The gsql prompt can be set using the three variables in Table 3. These variables consist of characters and special escape characters.

    Table 3 Prompt variables

    Variable

    Description

    Example

    PROMPT1

    Specifies the normal prompt used when gsql requests a new command.

    The default value of PROMPT1 is:

    %/%R%#

    PROMPT1 can be used to change the prompt.

    • Change the prompt to [local]:
      openGauss=> \set PROMPT1 %M
      [local:/tmp/gaussdba_mppdb]
    • Change the prompt to name:
      openGauss=> \set PROMPT1 name
      name
    • Change the prompt to =:
      openGauss=> \set PROMPT1 %R
      =

    PROMPT2

    Specifies the prompt displayed when more input is expected because the command that is not terminated with a semicolon (;) or a quote (") is not closed.

    PROMPT2 can be used to display the prompt.

    openGauss=# \set PROMPT2 TEST
    openGauss=# select * from HR.areaS TEST;
     area_id |       area_name    
    ---------+--------------------
           1 | Europe
           2 | Americas
           4 | Middle East and Africa
           3 | Asia
    (4 rows))

    PROMPT3

    Specifies the prompt displayed when the COPY statement (such as COPY FROM STDIN) is run and data input is expected.

    PROMPT3 can be used to display the COPY prompt.

    openGauss=# \set PROMPT3 '>>>>'
    openGauss=# copy HR.areaS from STDIN;
    Enter data to be copied followed by a newline.
    End with a backslash and a period on a line by itself.
    >>>>1 aa
    >>>>2 bb
    >>>>\.

    The value of the selected prompt variable is printed literally. However, a value containing a percent sign (%) is replaced by the predefined contents depending on the character following the percent sign (%). For details about the defined substitutions, see Table 4.

    Table 4 Defined substitutions

    Symbol

    Description

    %M

    Replaced with the full host name (with domain name). The full name is [local] if the connection is over a Unix domain socket, or [local:/dir/name] if the Unix domain socket is not at the compiled default location.

    %m

    Replaced with the host name truncated at the first dot. It is [local] if the connection is over a Unix domain socket.

    %>

    Replaced with the number of the port that the host is listening on.

    %n

    Replaced with the database session username.

    %/

    Replaced with the name of the current database.

    %~

    Similar to %/. However, the output is tilde (~) if the database is your default database.

    %#

    Uses # if the session user is the database administrator. Otherwise, uses >.

    %R

    • In PROMPT1 normally =, but ^ if in single-line mode, or ! if the session is disconnected from the database (which can happen if \connect fails).
    • In PROMPT2 %R is replaced with a hyphen (-), an asterisk (*), a single or double quotation mark, or a dollar sign ($), depending on whether gsql expects more input because the query is inside a /*...*/ comment or inside a quoted or dollar-escaped string.

    %x

    Replaced with the transaction status.

    • An empty string when it is not in a transaction block
    • An asterisk (*) when it is in a transaction block
    • An exclamation mark (!) when it is in a failed transaction block
    • A question mark (?) when the transaction status is indefinite (for example, because there is no connection).

    %digits

    Replaced with the character with the specified byte.

    %:name

    Replaced with the value of the name variable of gsql.

    %command

    Replaced with the command output, similar to substitution with the "^" symbol.

    %[ . . . %]

    Prompts may contain terminal control characters which, for example, change the color, background, or style of the prompt text, or change the title of the terminal window. For example:

    potgres=> \set PROMPT1 '%[%033[1;33;40m%]%n@%/%R%[%033[0m%]%#'

    The output is a boldfaced (1;) yellow-on-black (33;40) prompt on VT100-compatible, color-capable terminals.

Environment Variables

Table 5 Environment variables related to gsql

Name

Description

COLUMNS

If \set columns is set to 0, this parameter controls the width of the wrapped format. This width determines whether to change the wide output mode into the vertical output mode if automatic expansion is enabled.

PAGER

If the query results do not fit on the screen, they are redirected through this command. You can use the \pset command to disable the pager. Typically, the more or less command is used for viewing the query result page by page. The default is platform-dependent.

NOTE:

Display of the less command is affected by the LC_CTYPE environment variable.

PSQL_EDITOR

The \e and \ef commands use the editor specified by the environment variables. The variables are examined in the order listed. The default editor on Unix is vi.

EDITOR

VISUAL

PSQL_EDITOR_LINENUMBER_ARG

When the \e or \ef command is used with a line number parameter, this variable specifies the command-line parameter used to pass the starting line number to the editor. For editors, such as Emacs or vi, this is a plus sign. Include a space in the value of the variable if space is needed between the option name and the line number. For example:
PSQL_EDITOR_LINENUMBER_ARG = '+'  
PSQL_EDITOR_LINENUMBER_ARG='--line '

A plus sign (+) is used by default on Unix.

PSQLRC

Specifies the location of the user's .gsqlrc file.

SHELL

Has the same effect as the \! command.

TMPDIR

Specifies the directory for storing temporary files. The default value is /tmp.

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