Trim Trailing Spaces with Postgresql

Trim trailing spaces with PostgreSQL

There are many different invisible characters. Many of them have the property WSpace=Y ("whitespace") in Unicode. But some special characters are not considered "whitespace" and still have no visible representation. The excellent Wikipedia articles about space (punctuation) and whitespace characters should give you an idea.

<rant>Unicode sucks in this regard: introducing lots of exotic characters that mainly serve to confuse people.</rant>

The standard SQL trim() function by default only trims the basic Latin space character (Unicode: U+0020 / ASCII 32). Same with the rtrim() and ltrim() variants. Your call also only targets that particular character.

Use regular expressions with regexp_replace() instead.

Trailing

To remove all trailing white space (but not white space inside the string):

SELECT regexp_replace(eventdate, '\s+$', '') FROM eventdates;

The regular expression explained:

\s ... regular expression class shorthand for [[:space:]]

    - which is the set of white-space characters - see limitations below

+ ... 1 or more consecutive matches

$ ... end of string

Demo:

SELECT regexp_replace('inner white   ', '\s+$', '') || '|'

Returns:

inner white|

Yes, that's a single backslash (\). Details in this related answer:

• SQL select where column begins with \

Leading

To remove all leading white space (but not white space inside the string):

regexp_replace(eventdate, '^\s+', '')

^ .. start of string

Both

To remove both, you can chain above function calls:

regexp_replace(regexp_replace(eventdate, '^\s+', ''), '\s+$', '')

Or you can combine both in a single call with two branches.

Add 'g' as 4th parameter to replace all matches, not just the first:

regexp_replace(eventdate, '^\s+|\s+$', '', 'g')

But that should typically be faster with substring():

substring(eventdate, '\S(?:.*\S)*')

\S ... everything but white space

(?:re) ... non-capturing set of parentheses

.* ... any string of 0-n characters

Or one of these:

substring(eventdate, '^\s*(.*\S)')
substring(eventdate, '(\S.*\S)')  -- only works for 2+ printing characters

(re) ... Capturing set of parentheses

Effectively takes the first non-whitespace character and everything up to the last non-whitespace character if available.

Whitespace?

There are a few more related characters which are not classified as "whitespace" in Unicode - so not contained in the character class [[:space:]].

These print as invisible glyphs in pgAdmin for me: "mongolian vowel", "zero width space", "zero width non-joiner", "zero width joiner":

SELECT E'\u180e', E'\u200B', E'\u200C', E'\u200D';

'᠎' | '​' | '‌' | '‍'

Two more, printing as visible glyphs in pgAdmin, but invisible in my browser: "word joiner", "zero width non-breaking space":

SELECT E'\u2060', E'\uFEFF';
'⁠' | ''

Ultimately, whether characters are rendered invisible or not also depends on the font used for display.

To remove all of these as well, replace '\s' with '[\s\u180e\u200B\u200C\u200D\u2060\uFEFF]' or '[\s᠎​‌‍⁠]' (note trailing invisible characters!).

Example, instead of:

regexp_replace(eventdate, '\s+$', '')

use:

regexp_replace(eventdate, '[\s\u180e\u200B\u200C\u200D\u2060\uFEFF]+$', '')

or:

regexp_replace(eventdate, '[\s᠎​‌‍⁠]+$', '')  -- note invisible characters

Limitations

There is also the Posix character class [[:graph:]] supposed to represent "visible characters". Example:

substring(eventdate, '([[:graph:]].*[[:graph:]])')

It works reliably for ASCII characters in every setup (where it boils down to [\x21-\x7E]), but beyond that you currently (incl. pg 10) depend on information provided by the underlying OS (to define ctype) and possibly locale settings.

Strictly speaking, that's the case for every reference to a character class, but there seems to be more disagreement with the less commonly used ones like graph. But you may have to add more characters to the character class [[:space:]] (shorthand \s) to catch all whitespace characters. Like: \u2007, \u202f and \u00a0 seem to also be missing for @XiCoN JFS.

The manual:

Within a bracket expression, the name of a character class enclosed in
[: and :] stands for the list of all characters belonging to that
class. Standard character class names are: alnum, alpha, blank, cntrl,
digit, graph, lower, print, punct, space, upper, xdigit.
These stand for the character classes defined in ctype.
A locale can provide others.

Bold emphasis mine.

Also note this limitation that was fixed with Postgres 10:

Fix regular expressions' character class handling for large character
codes, particularly Unicode characters above U+7FF (Tom Lane)

Previously, such characters were never recognized as belonging to
locale-dependent character classes such as [[:alpha:]].

Prevent trailing spaces during insert?

Use the PostgreSQL trim() function.

There is trim(), rtrim() and ltrim().
To trim trailing spaces:

...
rtrim(b.acct_type_desc) as acct_desc,
...

If acct_type_desc is not of type text or varchar, cast it to text first:

...
rtrim(b.acct_type_desc::text) as acct_desc,
...

If acct_type_desc is of type char(n), casting it to text removes trailing spaces automatically, no trim() necessary.

How to trim/remove leading/left white spaces from a text file using Windows Batch?

Have a look at the -t and -A psql parameters:

• -t removes headers and footers from the results
• -A switches off aligned mode (which is most likely where your whitespace is coming from - alignment into columns).

So the command should look something like the following:

psql -d databasename -p portname -U username -t -A -f filename -o "C:\text.txt"

So, basically, you shouldn't need to modify the resulting file - you can modify your psql command to get results in a format you want.

how to trim trailing spaces from every columns in all tables in PostgreSQL database

Following query will return all tables and their columns that may or may not have trailing spaces.


NOTE : I'm assuming that all tables have tbl_ prefix.

 select 
     table_name,COLUMN_NAME
 from 
     INFORMATION_SCHEMA.COLUMNS 
 where 
     table_name LIKE 'tbl_%' and (data_type='text' or data_type='character varying')

to get the UPDATE query for all tables use the following select

select 
       'UPDATE '||quote_ident(c.table_name)||' SET '||c.COLUMN_NAME||'=TRIM('||quote_ident(c.COLUMN_NAME)||')  
        WHERE '||quote_ident(c.COLUMN_NAME)||' ILIKE ''% '' ' as script
from (
        select 
           table_name,COLUMN_NAME
        from 
           INFORMATION_SCHEMA.COLUMNS 
        where 
           table_name LIKE 'tbl_%' and (data_type='text' or data_type='character varying')
     ) c

This will return rows like
update tbl_sale set product=trim(product) where product LIKE '% ' to update all columns in all tables.

---

Finally,

Use this method to update all columns in a database that having trailing space.

do $$
declare
    selectrow record;
begin
for selectrow in
select 
       'UPDATE '||quote_ident(c.table_name)||' SET '||c.COLUMN_NAME||'=TRIM('||c.COLUMN_NAME||')  WHERE '||quote_ident(c.COLUMN_NAME)||' ILIKE ''% '' ' as script
from (
       select 
          table_name,COLUMN_NAME
       from 
          INFORMATION_SCHEMA.COLUMNS 
       where 
          table_name LIKE 'tbl_%'  and (data_type='text' or data_type='character varying' )
     ) c
loop
execute selectrow.script;
end loop;
end;
$$;

Wrap the above method into a Function, So that it is more convenient to use future

create function rm_trail_spaces() returns void as 
   $$

    declare
        selectrow record;
    begin
    for selectrow in
    select 
           'UPDATE '||quote_ident(c.table_name)||' SET '||quote_ident(c.COLUMN_NAME)||'=TRIM('||quote_ident(c.COLUMN_NAME)||')  WHERE '||quote_ident(c.COLUMN_NAME)||' ILIKE ''% '' ' as script
    from (
           select 
              table_name,COLUMN_NAME
           from 
              INFORMATION_SCHEMA.COLUMNS 
           where 
              table_name LIKE 'tbl_%'  and (data_type='text' or data_type='character varying' )
         ) c
    loop
    execute selectrow.script;
    end loop;
    end;
  $$
  language plpgsql   

usage: SELECT rm_trail_spaces()
           

How to show leading/trailing whitespace in a PostgreSQL column?

If you don't mind substituting all whitespace characters whether or not they are leading/trailing, something like the following will do it:

SELECT REPLACE(REPLACE(REPLACE(REPLACE(txt, ' ', '_'),
                               E'\t', '\t'),
                       E'\r', '\r'),
               E'\n', '\n') AS txt
FROM test;

This is using an underscore to mark the spaces but of course you are free to choose your own. See SQL fiddle demo.

If you strictly only want to show up the leading/trailing ones it will get more complex - but if this is really desired, something may be possible using regex_replace.

PostgreSQL regexp_replace() to keep just one whitespace

SELECT trim(regexp_replace(col_name, '\s+', ' ', 'g')) as col_name FROM table_name;

Or In case of update :

UPDATE table_name SET col_name = trim(regexp_replace(col_name, '\s+', ' ', 'g'));

The regexp_replace is flags are described on this section of the documentation.

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