Exactly what data does pspg receive from psql?

Question

Exactly what data does pspg receive from psql?

velle opened this issue a year ago · comments

Consider the following command:

$ psql -c "SELECT * FROM foo"
 gid | id |                                                                        geom                                                                        
-----+----+----------------------------------------------------------------------------------------------------------------------------------------------------
   1 |  1 | 01020000000400000000000000000024400000000000000000000000000000244000000000000049400000000000003440000000000000494000000000000034400000000000000000
   2 |  2 | 0102000000040000000000000000003E4000000000000000000000000000003E4000000000008051400000000000004940000000000080514000000000000049400000000000000000
(2 rows)

I can use pspg in two ways

$ psql -c "SELECT * FROM cubetown.LS_c" | pspg
$ PAGER=pspg psql -c "SELECT * FROM cubetown.LS_c"

Are they equivalent?

In both cases, does pgsg simply receive the output as a ascii-formatted table (using vertical pipe symbol, spaces and newlines)? Or does pspg receive the data in another format? Does the data received by pgps contain data (in addition to what I can see when printed directly to terminal), eg metadata such as datatype for each column that could hint how to format the data in the most user-friendly way?

I am asking about this in order to figure out, if I can customize pspg to do what I am trying to achieve :)

Sincerely

Pavel Stehule · Answer 1 · Thu Jul 13 2023 18:56:20 GMT+0800 (China Standard Time)

Hi čt 13. 7. 2023 v 11:56 odesílatel velle ***@***.***> napsal:

Consider the following command: $ psql -c "SELECT * FROM foo" gid | id | geom -----+----+---------------------------------------------------------------------------------------------------------------------------------------------------- 1 | 1 | 01020000000400000000000000000024400000000000000000000000000000244000000000000049400000000000003440000000000000494000000000000034400000000000000000 2 | 2 | 0102000000040000000000000000003E4000000000000000000000000000003E4000000000008051400000000000004940000000000080514000000000000049400000000000000000 (2 rows) I can use pspg in two ways - $ psql -c "SELECT * FROM cubetown.LS_c" | pspg - $ PAGER=pspg psql -c "SELECT * FROM cubetown.LS_c" Are they equivalent?

yes, for pspg's perspective they are same pspg can read csv too. So you can do psql -c "SELECT .." --csv | pspg --csv

In both cases, does pgsg simply receive the output as a ascii-formatted table (using vertical pipe symbol, spaces and newlines)? Or does pspg receive the data in another format? Does the data received by pgps contain data (in addition to what I can see when printed directly to terminal), eg metadata such as datatype for each column that could hint how to format the data in the most user-friendly way?

The default format is just plain text - psql returns only a formatted table (in plain text) without metadata or any invisible data.

I am asking about this in order to figure out, if I can customize pspg to do what I am trying to achieve :)

pspg can work as a postgres client directly when pspg was compiled with libpq support. pspg -d postgres -h localhost -q "select * from ..." Sincerely

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The best input format (for pspg) is output of psql with settings \pset linestyle unicode \pset border 2 \pset null ∅