Overview

Basic Functions

  • Connect to the database: Use the gsql client to remotely connect to the GaussDB(DWS) database.

    Note

    If the gsql client 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

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 a variable, run the following command:

\unset varname

Note

  • A variable is a key-value pair. The value length is determined by the special variable VAR_MAX_LENGTH. For details, see Table 2.

  • 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 Variable.

SQL substitution

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

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

Customized prompt

Prompts of gsql can be customized. Prompts can be modified by changing the reserved 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.

Client operation history record

gsql records client operation history. 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 statements 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.

  • Variable

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

    \set foo bar

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

    \echo :foo
bar

    This variable quotation method is suitable for regular SQL statements and meta-commands.

    When the CLI parameter --dynamic-param (for details, see Table 1) is used or the special variable DYNAMIC_PARAM_ENABLE (for details, see Table 2) is set to true, you can execute the SQL statement to set the variable. The variable name is the column name in the SQL execution result and can be referenced using ${}. For example:

    \set DYNAMIC_PARAM_ENABLE true
SELECT 'Jack' AS "Name";
 Name
------
 Jack
(1 row)

\echo ${Name}
Jack

    In the preceding example, the SELECT statement is used to set the Name variable, and the ${} referencing method is used to obtain the value of the Name variable. In this example, the special variable DYNAMIC_PARAM_ENABLE controls this function. You can also use the CLI parameter --dynamic-param to control this function, for example, gsql -d postgres -p 25308 --dynamic-param -r.

    Note

    • Do not set variables when the SQL statement execution fails.

    • If the SQL statement execution result is empty, set the column name as a variable and assign it with an empty string.

    • If the SQL statement execution result is a record, set the column name as a variable and assign it with the corresponding string.

    • If the SQL statement execution result contains multiple records, set the column name as a variable concatenated by specific characters, and then assign the value to the variable. The special variable RESULT_DELIMITER (for details, see Table 2) determines the specific character. The default delimiter is a comma (,).

    Examples of setting variables by executing SQL statements:

    \set DYNAMIC_PARAM_ENABLE true
CREATE TABLE student (id INT, name VARCHAR(32)) DISTRIBUTE BY HASH(id);
CREATE TABLE
INSERT INTO student VALUES (1, 'Jack'), (2, 'Tom'), (3, 'Jerry');
INSERT 0 3
-- Do not set variables when the SQL statement execution fails.
SELECT id, name FROM student ORDER BY idi;
ERROR:  column "idi" does not exist
LINE 1: SELECT id, name FROM student ORDER BY idi;
                                              ^
\echo ${id} ${name}
${id} ${name}

-- If the execution result contains multiple records, use specific characters to concatenate the values.
SELECT id, name FROM student ORDER BY id;
 id | name
----+-------
  1 | Jack
  2 | Tom
  3 | Jerry
(3 rows)

\echo ${id} ${name}
1,2,3 Jack,Tom,Jerry

-- If the execution result contains only one record, execute the following statement to set the variable:
SELECT id, name FROM student where id = 1;
 id | name
----+------
  1 | Jack
(1 row)

\echo ${id} ${name}
1 Jack

-- If the execution result is empty, assign the variable with an empty string as follows:
SELECT id, name FROM student where id = 4;
 id | name
----+------
(0 rows)

\echo ${id} ${name}

    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 all special variables, see Table 2.

    Note

    • All the special variables consist of uppercase 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 Setting special variables

    Variable

    Setting Method

    Description

    DBNAME

    \set DBNAME dbname

    Specifies the name of a 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

    Specifies the 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

    Setting this variable to a proper value reduces memory usage. Generally, values from 100 to 1000 are proper.

    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 in the history command. 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 (the 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 connected database user.

    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 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.

    VAR_NOT_FOUND

    \set VAR_NOT_FOUND default | null | error

    You can set this parameter to default, null, or error to control the processing mode when the referenced variable does not exist.

    • default: Do not replace the variable and retain the original character string.

    • null: Replace the original character string with an empty character string.

    • error: Output error information and retain the original character string.

    VAR_MAX_LENGTH

    \set VAR_MAX_LENGTH variable

    Specifies the variable value length. The default value is 4096. If the length of a variable value exceeds the specified parameter value, the variable value is truncated and an alarm is generated.

    ERROR_LEVEL

    \set ERROR_LEVEL transaction | statement

    Indicates whether a transaction or statement is successful or not. Value options: transaction or statement. Default value: transaction

    • statement: ERROR records whether the previous SQL statement is executed successfully.

    • transaction: ERROR records whether the previous SQL statement is successfully executed or whether an error occurs during the execution of the previous transaction.

    ERROR

    \set ERROR true | false

    Indicates whether the previous SQL statement is successfully executed or whether an error occurs during the execution of the previous transaction. false: succeeded. true: failed. default value: false The setting can be updated by executing SQL statements. You are not advised to manually set this parameter.

    LAST_ERROR_SQLSTATE

    \set LAST_ERROR_SQLSTATE state

    Error code of the previously failed SQL statement execution. The default value is 00000. The setting can be updated by executing SQL statements. You are not advised to manually set this parameter.

    LAST_ERROR_MESSAGE

    \set LAST_ERROR_MESSAGE message

    Error message of the previously failed SQL statement execution. The default value is an empty string. The setting can be updated by executing SQL statements. You are not advised to manually set this parameter.

    ROW_COUNT

    \set ROW_COUNT count

    • If ERROR_LEVEL is set to statement, this parameter indicates the number of rows returned after the previous SQL statement is executed or the number of affected rows.

    • If ERROR_LEVEL is set to transaction and an internal error occurs when a transaction ends, this parameter indicates the number of rows returned by the last SQL statement of the transaction or the number of affected rows. Otherwise, this parameter indicates the number of rows returned by the last SQL statement or the number of affected rows.

    If the SQL statement fails to be executed, set this parameter to 0. The default value is 0. The setting can be updated by executing SQL statements. You are not advised to manually set this parameter.

    SQLSTATE

    \set SQLSTATE state

    • If ERROR_LEVEL is set to statement, this parameter indicates the status code of the previous SQL statement.

    • If ERROR_LEVEL is set to transaction and an internal error occurs when a transaction ends, this parameter indicates the status code of the last SQL statement in the transaction. Otherwise, this parameter indicates the status code of the previous SQL statement.

    The default value is 00000. The setting can be updated by executing SQL statements. You are not advised to manually set this parameter.

    LAST_SYS_CODE

    \set LAST_SYS_CODE code

    Returned value of the previous system command execution. The default value is 0. The setting can be updated by using the meta-command \! to run the system command. You are not advised to manually set this parameter.

    DYNAMIC_PARAM_ENABLE

    \set DYNAMIC_PARAM_ENABLE true | false

    Controls the generation of variables and the variable referencing method ${} during SQL statement execution. The default value is false.

    • true: Generate variables when executing SQL statements, and support the ${} variable referencing method.

    • false: Do not generate variables when executing SQL statements, and the ${} variable referencing method is not supported either.

    CONVERT_QUOTE_IN_DYNAMIC_PARAM

    \set CONVERT_QUOTE_IN_DYNAMIC_PARAM true | false

    Specifies whether to escape single quotation marks, double quotation marks, and backslashes during dynamic variable parsing. The default value is true.

    • true: Indicates that during dynamic variable parsing, single quotation marks, double quotation marks, and backslashes (\) need to be escaped, and SQL substitution automatically escapes quotation marks and backslashes in variables.

    • false: Indicates that during dynamic variable parsing single quotation marks, double quotation marks, and backslashes (\) do not need to be escaped. SQL substitution does not process strings in variables. You need to manually escape them as needed.

    For details about the usage example, see CONVERT_QUOTE_IN_DYNAMIC....

    RESULT_DELIMITER

    \set RESULT_DELIMITER delimiter

    Controls the delimiter used for concatenating multiple records when variables are generated during SQL statement execution. The default delimiter is comma (,).

    COMPARE_STRATEGY

    \set COMPARE_STRATEGY default | natural | equal

    Used to specify the value comparison policy of the \if expression. The default value is default.

    • default: Specifies the default comparison policy. Only strings or numbers can be compared, and strings cannot be compared with numbers. Parameters inside single quotation marks (') are identified as strings, and parameters outside single quotation marks (') are identified as numbers.

    • natural: The default comparison policy is supported, and parameters that contain dynamic variables are identified as strings. When one side of the comparison operator is a number, try to convert the other side to a number, and then compare the numbers on both sides. If the conversion fails, an error is reported and the comparison result is false.

    • equal: Only the equality comparison is supported. The comparison is performed based on strings.

    For details, see if conditional block comparison rules and examples.

    COMMAND_ERROR_STOP

    \set COMMAND_ERROR_STOP on | off

    Determines whether to report the error and stop executing the meta-command when an error occurs during meta-command execution. By default, the meta-command execution is not stopped.

    For details, see the example of using COMMAND_ERROR_STOP.

    • The following is an example of using the special variables ERROR_LEVEL and ERROR:

    When ERROR_LEVEL is set to statement, ERROR records whether the previous SQL statement is executed successfully. In the following example, when an SQL execution error occurs in a transaction and the transaction ends, the value of ERROR is false. In this case, ERROR only records whether the previous SQL statement ends successfully.

    \set ERROR_LEVEL statement
begin;
BEGIN
select 1 as ;
ERROR:  syntax error at or near ";"
LINE 1: select 1 as ;
                    ^
end;
ROLLBACK
\echo :ERROR
false

    When ERROR_LEVEL is set to transaction, ERROR can be used to capture SQL execution errors in a transaction. In the following example, when an SQL execution error occurs in a transaction and the transaction ends, the value of ERROR is true.

    \set ERROR_LEVEL transaction
begin;
BEGIN
select 1 as ;
ERROR:  syntax error at or near ";"
LINE 1: select 1 as ;
                    ^
end;
ROLLBACK
\echo :ERROR
true

    • The following is an example of using the special variable COMMAND_ERROR_STOP:

    When COMMAND_ERROR_STOP is set to on and an error occurs during the meta-command execution, the error is reported and the meta-command execution is stopped. When this function is enabled, the execution error of the meta-command can be effectively detected.

    When COMMAND_ERROR_STOP is set to off and an error occurs during the meta-command execution, related information is printed and the script continues to be executed.

    \set COMMAND_ERROR_STOP on
\i /home/omm/copy_data.sql

select id, name from student;

    When COMMAND_ERROR_STOP in the preceding script is set to on, an error message is displayed after the error is reported, and the script execution is stopped.

    gsql:test.sql:2: /home/omm/copy_data.sql: Not a directory

    When COMMAND_ERROR_STOP is set to off, an error message is displayed after the error is reported, and the SELECT statement continues to be executed.

    gsql:test.sql:2: /home/omm/copy_data.sql: Not a directory
 id | name
----+------
  1 | Jack
(1 row)

  • 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 (:) in front of the variable. For example:

    \set foo 'HR.areaS'
select * from :foo;
 area_id |       area_name
---------+------------------------
       4 | Iron
       3 | Desert
       1 | Wood
       2 | Lake
(4 rows)

    The above command queries the HR.areaS table.

    Important

    The value of a variable is copied character by character, and even an asymmetric quote mark or backslash (\) is copied. Therefore, the input content must be meaningful.

    • The following is an example of using the special variable CONVERT_QUOTE_IN_DYNAMIC_PARAM:

    If CONVERT_QUOTE_IN_DYNAMIC_PARAM is set to true, quotation marks and backslashes in variables are automatically escaped during SQL substitution.

     \set DYNAMIC_PARAM_ENABLE true
 \set CONVERT_QUOTE_IN_DYNAMIC_PARAM true
 select '""abc''''\\' as "SpecialCharacters";
   test
-----------
 ""abc''\\
(1 row)

-- Single quotation marks are escaped, but still displayed in the result.
 select '${SpecialCharacters}' as "test";
   test
-----------
 ""abc''\\
(1 row)

-- Single quotation marks and backslashes are escaped, but still displayed in the result.
 select E'${SpecialCharacters}' as "test";
   test
-----------
 ""abc''\\
(1 row)

-- Double quotation marks are escaped, but still displayed in the result.
-- The column name contains characters other than letters, digits, and underscores (_). Therefore, an error occurred.
 select 'test' as "${SpecialCharacters}";
error while saving the value of ""abc''\\, please check the column name which can only contain upper and lower case letters, numbers and '_'.
 ""abc''\\
-----------
 test
(1 row)

    When CONVERT_QUOTE_IN_DYNAMIC_PARAM is set to false, strings in the variable are not processed during SQL substitution. You need to manually escape the strings as needed

    Note

    You are advised to use the default value true.

    During SQL substitution, single quotation marks need to be escaped in '', single quotation marks and backslashes need to be escaped in E'', and double quotation marks need to be escaped in "". Quotation marks and backslashes need to be handled based on variable positions. This makes the variable logics in SQL substitution complex and error-prone.

     \set DYNAMIC_PARAM_ENABLE true
 \set CONVERT_QUOTE_IN_DYNAMIC_PARAM false
 select '""abc''''\\' as "SpecialCharacters";
   test
-----------
 ""abc''\\
(1 row)

-- Single quotation marks are not escaped. The result contains only one single quotation mark.
 select '${SpecialCharacters}' as "test";
   test
----------
 ""abc'\\
(1 row)

-- Single quotation marks and backslashes are not escaped. The result contains only one single quotation mark and one backslash.
 select E'${SpecialCharacters}' as "test";
  test
---------
 ""abc'\
(1 row)

-- Double quotation marks are not escaped. The result contains only one double quotation mark.
-- The column name contains characters other than letters, digits, and underscores (_). Therefore, an error occurred.
 select 'test' as "${SpecialCharacters}";
error while saving the value of "abc''\\, please check the column name which can only contain upper and lower case letters, numbers and '_'.
 "abc''\\
----------
 test
(1 row)

  • 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]:

      \set PROMPT1 %M
[local:/tmp/gaussdba_mppdb]

    • Change the prompt to name:

      \set PROMPT1 name
name

    • Change the prompt to =:

      \set PROMPT1 %R
=

    PROMPT2

    Specifies the prompt displayed when more command input is expected. For example, it is expected if a command is not terminated with a semicolon (;) or a quote (") is not closed.

    PROMPT2 can be used to display the prompt:

    \set PROMPT2 TEST
select * from HR.areaS TEST;
 area_id |       area_name
---------+--------------------
       1 | Wood
       2 | Lake
       4 | Iron
       3 | Desert
(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.

    \set PROMPT3 '>>>>'
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

    Specifies 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

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

    %>

    Specifies the number of the port that the host is listening on.

    %n

    Specifies the database session user name.

    %/

    Specifies the name of the current database.

    %~

    Is 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

    • Normally uses = for PROMPT1, but ^ in single-line mode and ! if the session is disconnected from the database (which may occur if \connect fails).

    • For PROMPT2, the sequence is replaced by a hyphen (-), asterisk (*), single quotation mark ('), double quotation mark ("), or dollar sign ($), depending on whether gsql is waiting for more input, or the query is not terminated, or the query is in the /* ... */ the comment, quotation mark, or dollar sign extension.

    %x

    Specifies 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 indeterminate (for example, indeterminate due to no connections).

    %digits

    Is replaced with the character with the specified byte.

    %:name

    Specifies the value of the name variable of gsql.

    %command

    Specifies command output, similar to ordinary "back-tick" ("^") substitution.

    %[ . . . %]

    Prompts can 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 the width output mode is changed to a vertical bar format in automatic expansion mode.

PAGER

If the query result cannot be displayed within one page, the query result will be redirected to the 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 value is platform-associated.

Note

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

PSQL_EDITOR

The \e and \ef commands use the editor specified by the environment variables. Variables are checked according to the list sequence. 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. A space is added behind the value of the variable if whitespace is required 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.

last updated: 2024-12-11 14:09 UTC - commit: 68b0697a99ca2a4acec84bb31c0962598d3b4a14