$ psql "service=myservice sslmode=require"
$ psql postgresql://dbmaster:5433/mydb?sslmode=require

$ psql testdb
psql (16.1)
Type "help" for help.
testdb=>

Example:

INSERT INTO tbl1 VALUES ($1, $2) \bind 'first value' 'second value' \g

This also works for query-execution commands besides \g, such as \gx and \gset.

This command causes the extended query protocol (see Section 55.1.2) to be used, unlike normal psql operation, which uses the simple query protocol. So this command can be useful to test the extended query protocol from psql. (The extended query protocol is used even if the query has no parameters and this command specifies zero parameters.) This command affects only the next query executed; all subsequent queries will use the simple query protocol by default.

Specifying any of dbname, username, host or port as - is equivalent to omitting that parameter.

The new connection can re-use connection parameters from the previous connection; not only database name, user, host, and port, but other settings such as sslmode. By default, parameters are re-used in the positional syntax, but not when a conninfo string is given. Passing a first argument of -reuse-previous=on or -reuse-previous=off overrides that default. If parameters are re-used, then any parameter not explicitly specified as a positional parameter or in the conninfo string is taken from the existing connection's parameters. An exception is that if the host setting is changed from its previous value using the positional syntax, any hostaddr setting present in the existing connection's parameters is dropped. Also, any password used for the existing connection will be re-used only if the user, host, and port settings are not changed. When the command neither specifies nor reuses a particular parameter, the libpq default is used.

If the new connection is successfully made, the previous connection is closed. If the connection attempt fails (wrong user name, access denied, etc.), the previous connection will be kept if psql is in interactive mode. But when executing a non-interactive script, the old connection is closed and an error is reported. That may or may not terminate the script; if it does not, all database-accessing commands will fail until another \connect command is successfully executed. This distinction was chosen as a user convenience against typos on the one hand, and a safety mechanism that scripts are not accidentally acting on the wrong database on the other hand. Note that whenever a \connect command attempts to re-use parameters, the values re-used are those of the last successful connection, not of any failed attempts made subsequently. However, in the case of a non-interactive \connect failure, no parameters are allowed to be re-used later, since the script would likely be expecting the values from the failed \connect to be re-used.

Examples:

=> \c mydb myuser host.dom 6432
=> \c service=foo
=> \c "host=localhost port=5432 dbname=mydb connect_timeout=10 sslmode=disable"
=> \c -reuse-previous=on sslmode=require    -- changes only sslmode
=> \c postgresql://tom@localhost/mydb?application_name=myapp

When program is specified, command is executed by psql and the data passed from or to command is routed between the server and the client. Again, the execution privileges are those of the local user, not the server, and no SQL superuser privileges are required.

For \copy ... from stdin, data rows are read from the same source that issued the command, continuing until \. is read or the stream reaches EOF. This option is useful for populating tables in-line within an SQL script file. For \copy ... to stdout, output is sent to the same place as psql command output, and the COPY count command status is not printed (since it might be confused with a data row). To read/write psql's standard input or output regardless of the current command source or \o option, write from pstdin or to pstdout.

The syntax of this command is similar to that of the SQL COPY command. All options other than the data source/destination are as specified for COPY. Because of this, special parsing rules apply to the \copy meta-command. Unlike most other meta-commands, the entire remainder of the line is always taken to be the arguments of \copy, and neither variable interpolation nor backquote expansion are performed in the arguments.

Each column specification can be a column number (starting at 1) or a column name. The usual SQL case folding and quoting rules apply to column names. If omitted, colV is taken as column 1 and colH as column 2. colH must differ from colV. If colD is not specified, then there must be exactly three columns in the query result, and the column that is neither colV nor colH is taken to be colD.

The vertical header, displayed as the leftmost column, contains the values found in column colV, in the same order as in the query results, but with duplicates removed.

The horizontal header, displayed as the first row, contains the values found in column colH, with duplicates removed. By default, these appear in the same order as in the query results. But if the optional sortcolH argument is given, it identifies a column whose values must be integer numbers, and the values from colH will appear in the horizontal header sorted according to the corresponding sortcolH values.

Inside the crosstab grid, for each distinct value x of colH and each distinct value y of colV, the cell located at the intersection (x,y) contains the value of the colD column in the query result row for which the value of colH is x and the value of colV is y. If there is no such row, the cell is empty. If there are multiple such rows, an error is reported.

For some types of relation, \d shows additional information for each column: column values for sequences, indexed expressions for indexes, and foreign data wrapper options for foreign tables.

The command form \d+ is identical, except that more information is displayed: any comments associated with the columns of the table are shown, as is the presence of OIDs in the table, the view definition if the relation is a view, a non-default replica identity setting and the access method name if the relation has an access method.

By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

\dd displays descriptions for objects matching the pattern, or of visible objects of the appropriate type if no argument is given. But in either case, only objects that have a description are listed. By default, only user-created objects are shown; supply a pattern or the S modifier to include system objects.

Descriptions for objects can be created with the COMMENT SQL command.

The ALTER DEFAULT PRIVILEGES command is used to set default access privileges. The meaning of the privilege display is explained in Section 5.7.

The GRANT and REVOKE commands are used to set access privileges. The meaning of the privilege display is explained in Section 5.7.

If the modifier n (“nested”) is used, or a pattern is specified, then non-root partitioned relations are included, and a column is shown displaying the parent of each partitioned relation.

If + is appended to the command name, the sum of the sizes of each relation's partitions is also displayed, along with the relation's description. If n is combined with +, two sizes are shown: one including the total size of directly-attached leaf partitions, and another showing the total size of all partitions, including indirectly attached sub-partitions.

The ALTER ROLE and ALTER DATABASE commands are used to define per-role and per-database configuration settings.

By default, only grants to user-created roles are shown; supply the S modifier to include system roles. If pattern is specified, only grants to those roles whose names match the pattern are listed.

The status of each kind of extended statistics is shown in a column named after its statistic kind (e.g. Ndistinct). defined means that it was requested when creating the statistics, and NULL means it wasn't requested. You can use pg_stats_ext if you'd like to know whether ANALYZE was run and statistics are available to the planner.

If you edit a file or the previous query, and you quit the editor without modifying the file, the query buffer is cleared. Otherwise, the new contents of the query buffer are re-parsed according to the normal rules of psql, treating the whole buffer as a single line. Any complete queries are immediately executed; that is, if the query buffer contains or ends with a semicolon, everything up to that point is executed and removed from the query buffer. Whatever remains in the query buffer is redisplayed. Type semicolon or \g to send it, or \r to cancel it by clearing the query buffer.

Treating the buffer as a single line primarily affects meta-commands: whatever is in the buffer after a meta-command will be taken as argument(s) to the meta-command, even if it spans multiple lines. (Thus you cannot make meta-command-using scripts this way. Use \i for that.)

If a line number is specified, psql will position the cursor on the specified line of the file or query buffer. Note that if a single all-digits argument is given, psql assumes it is a line number, not a file name.

=> \echo `date`
Tue Oct 26 21:40:57 CEST 1999

If the first argument is an unquoted -n the trailing newline is not written (nor is the first argument).

The target function can be specified by name alone, or by name and arguments, for example foo(integer, text). The argument types must be given if there is more than one function of the same name.

If no function is specified, a blank CREATE FUNCTION template is presented for editing.

If a line number is specified, psql will position the cursor on the specified line of the function body. (Note that the function body typically does not begin on the first line of the file.)

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \ef, and neither variable interpolation nor backquote expansion are performed in the arguments.

If no view is specified, a blank CREATE VIEW template is presented for editing.

If a line number is specified, psql will position the cursor on the specified line of the view definition.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \ev, and neither variable interpolation nor backquote expansion are performed in the arguments.

If parentheses appear after \g, they surround a space-separated list of option=value formatting-option clauses, which are interpreted in the same way as \pset option value commands, but take effect only for the duration of this query. In this list, spaces are not allowed around = signs, but are required between option clauses. If =value is omitted, the named option is changed in the same way as for \pset option with no explicit value.

If a filename or |command argument is given, the query's output is written to the named file or piped to the given shell command, instead of displaying it as usual. The file or command is written to only if the query successfully returns zero or more tuples, not if the query fails or is a non-data-returning SQL command.

If the current query buffer is empty, the most recently sent query is re-executed instead. Except for that behavior, \g without any arguments is essentially equivalent to a semicolon. With arguments, \g provides a “one-shot” alternative to the \o command, and additionally allows one-shot adjustments of the output formatting options normally set by \pset.

When the last argument begins with |, the entire remainder of the line is taken to be the command to execute, and neither variable interpolation nor backquote expansion are performed in it. The rest of the line is simply passed literally to the shell.

If the current query buffer is empty, the most recently sent query is described instead.

=> SELECT format('create index on my_table(%I)', attname)
-> FROM pg_attribute
-> WHERE attrelid = 'my_table'::regclass AND attnum > 0
-> ORDER BY attnum
-> \gexec
CREATE INDEX
CREATE INDEX
CREATE INDEX
CREATE INDEX

The generated queries are executed in the order in which the rows are returned, and left-to-right within each row if there is more than one column. NULL fields are ignored. The generated queries are sent literally to the server for processing, so they cannot be psql meta-commands nor contain psql variable references. If any individual query fails, execution of the remaining queries continues unless ON_ERROR_STOP is set. Execution of each query is subject to ECHO processing. (Setting ECHO to all or queries is often advisable when using \gexec.) Query logging, single-step mode, timing, and other query execution features apply to each generated query as well.

If the current query buffer is empty, the most recently sent query is re-executed instead.

=> SELECT 'hello' AS var1, 10 AS var2
-> \gset
=> \echo :var1 :var2
hello 10

If you specify a prefix, that string is prepended to the query's column names to create the variable names to use:

=> SELECT 'hello' AS var1, 10 AS var2
-> \gset result_
=> \echo :result_var1 :result_var2
hello 10

If a column result is NULL, the corresponding variable is unset rather than being set.

If the query fails or does not return one row, no variables are changed.

If the current query buffer is empty, the most recently sent query is re-executed instead.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \help, and neither variable interpolation nor backquote expansion are performed in the arguments.

If filename is - (hyphen), then standard input is read until an EOF indication or \q meta-command. This can be used to intersperse interactive input with input from files. Note that Readline behavior will be used only if it is active at the outermost level.

The \if and \elif commands read their argument(s) and evaluate them as a Boolean expression. If the expression yields true then processing continues normally; otherwise, lines are skipped until a matching \elif, \else, or \endif is reached. Once an \if or \elif test has succeeded, the arguments of later \elif commands in the same block are not evaluated but are treated as false. Lines following an \else are processed only if no earlier matching \if or \elif succeeded.

The expression argument of an \if or \elif command is subject to variable interpolation and backquote expansion, just like any other backslash command argument. After that it is evaluated like the value of an on/off option variable. So a valid value is any unambiguous case-insensitive match for one of: true, false, 1, 0, on, off, yes, no. For example, t, T, and tR will all be considered to be true.

Expressions that do not properly evaluate to true or false will generate a warning and be treated as false.

Lines being skipped are parsed normally to identify queries and backslash commands, but queries are not sent to the server, and backslash commands other than conditionals (\if, \elif, \else, \endif) are ignored. Conditional commands are checked only for valid nesting. Variable references in skipped lines are not expanded, and backquote expansion is not performed either.

All the backslash commands of a given conditional block must appear in the same source file. If EOF is reached on the main input file or an \include-ed file before all local \if-blocks have been closed, then psql will raise an error.

Here is an example:

-- check for the existence of two separate records in the database and store
-- the results in separate psql variables
SELECT


    EXISTS(SELECT 1 FROM customer WHERE customer_id = 123) as is_customer,


    EXISTS(SELECT 1 FROM employee WHERE employee_id = 456) as is_employee
\gset
\if :is_customer


    SELECT * FROM customer WHERE customer_id = 123;
\elif :is_employee


    \echo 'is not a customer but is an employee'


    SELECT * FROM employee WHERE employee_id = 456;
\else


    \if yes


        \echo 'not a customer or employee'


    \else


        \echo 'this will never print'


    \endif
\endif

foo=> \lo_import '/home/peter/pictures/photo.xcf' 'a picture of me'
lo_import 152801

The response indicates that the large object received object ID 152801, which can be used to access the newly-created large object in the future. For the sake of readability, it is recommended to always associate a human-readable comment with every object. Both OIDs and comments can be viewed with the \lo_list command.

Note that this command is subtly different from the server-side lo_import because it acts as the local user on the local file system, rather than the server's user and file system.

If the argument begins with |, then the entire remainder of the line is taken to be the command to execute, and neither variable interpolation nor backquote expansion are performed in it. The rest of the line is simply passed literally to the shell.

“Query results” includes all tables, command responses, and notices obtained from the database server, as well as output of various backslash commands that query the database (such as \d); but not error messages.

By default, \prompt uses the terminal for input and output. However, if the -f command line switch was used, \prompt uses standard input and standard output.

\pset without any arguments displays the current status of all printing options.

Adjustable printing options are:

border

columns

csv_fieldsep

expanded (or x)

fieldsep

fieldsep_zero

footer

format

linestyle

null

numericlocale

pager

pager_min_lines

recordsep

recordsep_zero

tableattr (or T)

title (or C)

tuples_only (or t)

unicode_border_linestyle

unicode_column_linestyle

unicode_header_linestyle

xheader_width

Illustrations of how these different formats look can be seen in Examples, below.

\set without any arguments displays the names and values of all currently-set psql variables.

Valid variable names can contain letters, digits, and underscores. See Variables below for details. Variable names are case-sensitive.

Certain variables are special, in that they control psql's behavior or are automatically set to reflect connection state. These variables are documented in Variables, below.

The target function can be specified by name alone, or by name and arguments, for example foo(integer, text). The argument types must be given if there is more than one function of the same name.

If + is appended to the command name, then the output lines are numbered, with the first line of the function body being line 1.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \sf, and neither variable interpolation nor backquote expansion are performed in the arguments.

If + is appended to the command name, then the output lines are numbered from 1.

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \sv, and neither variable interpolation nor backquote expansion are performed in the arguments.

Most variables that control psql's behavior cannot be unset; instead, an \unset command is interpreted as setting them to their default values. See Variables below.

If the argument begins with |, then the entire remainder of the line is taken to be the command to execute, and neither variable interpolation nor backquote expansion are performed in it. The rest of the line is simply passed literally to the shell.

If the current query buffer is empty, the most recently sent query is re-executed instead.

This is an alias for \dp (“display privileges”).

Unlike most other meta-commands, the entire remainder of the line is always taken to be the argument(s) of \!, and neither variable interpolation nor backquote expansion are performed in the arguments. The rest of the line is simply passed literally to the shell.

Normally, psql will dispatch an SQL command to the server as soon as it reaches the command-ending semicolon, even if more input remains on the current line. Thus for example entering

select 1; select 2; select 3;

will result in the three SQL commands being individually sent to the server, with each one's results being displayed before continuing to the next command. However, a semicolon entered as \; will not trigger command processing, so that the command before it and the one after are effectively combined and sent to the server in one request. So for example

select 1\; select 2\; select 3;

results in sending the three SQL commands to the server in a single request, when the non-backslashed semicolon is reached. The server executes such a request as a single transaction, unless there are explicit BEGIN/COMMIT commands included in the string to divide it into multiple transactions. (See Section 55.2.2.1 for more details about how the server handles multi-query strings.)

The various \d commands accept a pattern parameter to specify the object name(s) to be displayed. In the simplest case, a pattern is just the exact name of the object. The characters within a pattern are normally folded to lower case, just as in SQL names; for example, \dt FOO will display the table named foo. As in SQL names, placing double quotes around a pattern stops folding to lower case. Should you need to include an actual double quote character in a pattern, write it as a pair of double quotes within a double-quote sequence; again this is in accord with the rules for SQL quoted identifiers. For example, \dt "FOO""BAR" will display the table named FOO"BAR (not foo"bar). Unlike the normal rules for SQL names, you can put double quotes around just part of a pattern, for instance \dt FOO"FOO"BAR will display the table named fooFOObar.

Whenever the pattern parameter is omitted completely, the \d commands display all objects that are visible in the current schema search path — this is equivalent to using * as the pattern. (An object is said to be visible if its containing schema is in the search path and no object of the same kind and name appears earlier in the search path. This is equivalent to the statement that the object can be referenced by name without explicit schema qualification.) To see all objects in the database regardless of visibility, use *.* as the pattern.

Within a pattern, * matches any sequence of characters (including no characters) and ? matches any single character. (This notation is comparable to Unix shell file name patterns.) For example, \dt int* displays tables whose names begin with int. But within double quotes, * and ? lose these special meanings and are just matched literally.

A relation pattern that contains a dot (.) is interpreted as a schema name pattern followed by an object name pattern. For example, \dt foo*.*bar* displays all tables whose table name includes bar that are in schemas whose schema name starts with foo. When no dot appears, then the pattern matches only objects that are visible in the current schema search path. Again, a dot within double quotes loses its special meaning and is matched literally. A relation pattern that contains two dots (.) is interpreted as a database name followed by a schema name pattern followed by an object name pattern. The database name portion will not be treated as a pattern and must match the name of the currently connected database, else an error will be raised.

A schema pattern that contains a dot (.) is interpreted as a database name followed by a schema name pattern. For example, \dn mydb.*foo* displays all schemas whose schema name includes foo. The database name portion will not be treated as a pattern and must match the name of the currently connected database, else an error will be raised.

Advanced users can use regular-expression notations such as character classes, for example [0-9] to match any digit. All regular expression special characters work as specified in Section 9.7.3, except for . which is taken as a separator as mentioned above, * which is translated to the regular-expression notation .*, ? which is translated to ., and $ which is matched literally. You can emulate these pattern characters at need by writing ? for ., (R+|) for R*, or (R|) for R?. $ is not needed as a regular-expression character since the pattern must match the whole name, unlike the usual interpretation of regular expressions (in other words, $ is automatically appended to your pattern). Write * at the beginning and/or end if you don't wish the pattern to be anchored. Note that within double quotes, all regular expression special characters lose their special meanings and are matched literally. Also, the regular expression special characters are matched literally in operator name patterns (i.e., the argument of \do).

psql provides variable substitution features similar to common Unix command shells. Variables are simply name/value pairs, where the value can be any string of any length. The name must consist of letters (including non-Latin letters), digits, and underscores.

To set a variable, use the psql meta-command \set. For example,

testdb=> \set foo bar

sets the variable foo to the value bar. To retrieve the content of the variable, precede the name with a colon, for example:

testdb=> \echo :foo
bar

This works in both regular SQL commands and meta-commands; there is more detail in SQL Interpolation, below.

If you call \set without a second argument, the variable is set to an empty-string value. To unset (i.e., delete) a variable, use the command \unset. To show the values of all variables, call \set without any argument.

A number of these variables are treated specially by psql. They represent certain option settings that can be changed at run time by altering the value of the variable, or in some cases represent changeable state of psql. By convention, all specially treated variables' names consist of all upper-case ASCII letters (and possibly digits and underscores). To ensure maximum compatibility in the future, avoid using such variable names for your own purposes.

Variables that control psql's behavior generally cannot be unset or set to invalid values. An \unset command is allowed but is interpreted as setting the variable to its default value. A \set command without a second argument is interpreted as setting the variable to on, for control variables that accept that value, and is rejected for others. Also, control variables that accept the values on and off will also accept other common spellings of Boolean values, such as true and false.

The specially treated variables are:

AUTOCOMMIT

COMP_KEYWORD_CASE

DBNAME

ECHO

ECHO_HIDDEN

ENCODING

ERROR

FETCH_COUNT

HIDE_TABLEAM

HIDE_TOAST_COMPRESSION

HISTCONTROL

HISTFILE

\set HISTFILE ~/.psql_history-:DBNAME

HISTSIZE

HOST

IGNOREEOF

LASTOID

LAST_ERROR_MESSAGE
LAST_ERROR_SQLSTATE

ON_ERROR_ROLLBACK

ON_ERROR_STOP

PORT

PROMPT1
PROMPT2
PROMPT3

QUIET

ROW_COUNT

SERVER_VERSION_NAME
SERVER_VERSION_NUM

SHELL_ERROR

SHELL_EXIT_CODE

SHOW_ALL_RESULTS

SHOW_CONTEXT

SINGLELINE

SINGLESTEP

SQLSTATE

USER

VERBOSITY

VERSION
VERSION_NAME
VERSION_NUM

A key feature of psql variables is that you can substitute (“interpolate”) them into regular SQL statements, as well as the arguments of meta-commands. Furthermore, psql provides facilities for ensuring that variable values used as SQL literals and identifiers are properly quoted. The syntax for interpolating a value without any quoting is to prepend the variable name with a colon (:). For example,

testdb=> \set foo 'my_table'
testdb=> SELECT * FROM :foo;

would query the table my_table. Note that this may be unsafe: the value of the variable is copied literally, so it can contain unbalanced quotes, or even backslash commands. You must make sure that it makes sense where you put it.

When a value is to be used as an SQL literal or identifier, it is safest to arrange for it to be quoted. To quote the value of a variable as an SQL literal, write a colon followed by the variable name in single quotes. To quote the value as an SQL identifier, write a colon followed by the variable name in double quotes. These constructs deal correctly with quotes and other special characters embedded within the variable value. The previous example would be more safely written this way:

testdb=> \set foo 'my_table'
testdb=> SELECT * FROM :"foo";

Variable interpolation will not be performed within quoted SQL literals and identifiers. Therefore, a construction such as ':foo' doesn't work to produce a quoted literal from a variable's value (and it would be unsafe if it did work, since it wouldn't correctly handle quotes embedded in the value).

One example use of this mechanism is to copy the contents of a file into a table column. First load the file into a variable and then interpolate the variable's value as a quoted string:

testdb=> \set content `cat my_file.txt`
testdb=> INSERT INTO my_table VALUES (:'content');

(Note that this still won't work if my_file.txt contains NUL bytes. psql does not support embedded NUL bytes in variable values.)

Since colons can legally appear in SQL commands, an apparent attempt at interpolation (that is, :name, :'name', or :"name") is not replaced unless the named variable is currently set. In any case, you can escape a colon with a backslash to protect it from substitution.

The :{?name} special syntax returns TRUE or FALSE depending on whether the variable exists or not, and is thus always substituted, unless the colon is backslash-escaped.

The colon syntax for variables is standard SQL for embedded query languages, such as ECPG. The colon syntaxes for array slices and type casts are PostgreSQL extensions, which can sometimes conflict with the standard usage. The colon-quote syntax for escaping a variable's value as an SQL literal or identifier is a psql extension.

The prompts psql issues can be customized to your preference. The three variables PROMPT1, PROMPT2, and PROMPT3 contain strings and special escape sequences that describe the appearance of the prompt. Prompt 1 is the normal prompt that is issued when psql requests a new command. Prompt 2 is issued when more input is expected during command entry, for example because the command was not terminated with a semicolon or a quote was not closed. Prompt 3 is issued when you are running an SQL COPY FROM STDIN command and you need to type in a row value on the terminal.

The value of the selected prompt variable is printed literally, except where a percent sign (%) is encountered. Depending on the next character, certain other text is substituted instead. Defined substitutions are:

%M

%m

%>

%n

%/

%~

%#

%p

%R

%x

%l

%digits

%:name:

%`command`

%[ ... %]

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

%w

psql uses the Readline or libedit library, if available, for convenient line editing and retrieval. The command history is automatically saved when psql exits and is reloaded when psql starts up. Type up-arrow or control-P to retrieve previous lines.

You can also use tab completion to fill in partially-typed keywords and SQL object names in many (by no means all) contexts. For example, at the start of a command, typing ins and pressing TAB will fill in insert into. Then, typing a few characters of a table or schema name and pressing TAB will fill in the unfinished name, or offer a menu of possible completions when there's more than one. (Depending on the library in use, you may need to press TAB more than once to get a menu.)

Tab completion for SQL object names requires sending queries to the server to find possible matches. In some contexts this can interfere with other operations. For example, after BEGIN it will be too late to issue SET TRANSACTION ISOLATION LEVEL if a tab-completion query is issued in between. If you do not want tab completion at all, you can turn it off permanently by putting this in a file named .inputrc in your home directory:

$if psql
set disable-completion on
$endif

(This is not a psql but a Readline feature. Read its documentation for further details.)

The -n (--no-readline) command line option can also be useful to disable use of Readline for a single run of psql. This prevents tab completion, use or recording of command line history, and editing of multi-line commands. It is particularly useful when you need to copy-and-paste text that contains TAB characters.