Re: How to assemble all fields of (any) view into a string?

On 09/07/2016 03:32 PM, Ken Tanzer wrote:

On Wed, Sep 7, 2016 at 3:18 PM, Adrian Klaver <adrian.klaver@aklaver.com
<mailto:adrian.klaver@aklaver.com>> wrote:

    On 09/07/2016 01:36 PM, Ken Tanzer wrote:



        On Wed, Sep 7, 2016 at 1:22 PM, Adrian Klaver
        <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
        <mailto:adrian.klaver@aklaver.com

        <mailto:adrian.klaver@aklaver.com>>> wrote:

            On 09/07/2016 01:15 PM, Ken Tanzer wrote:

                Hi.  Using version 9.2.  I'm trying to create a function
        that
                will take
                a record from any view and assemble it into a string,
        for export to
                another system.  For example, this view:

                    \d ebh_gain

                            View "public.ebh_gain"
                      Column       |     Type      | Modifiers
                -------------------+---------------+-----------
                 reporting_unit_id | character(3)  |
                 case_id           | character(10) |
                 event_date        | character(8)  |
                 ids_score         | character(1)  |
                 eds_score         | character(1)  |
                 sds_score         | character(1)  |
                 kc_auth_number    | integer       |
                 king_county_id    | integer       |

                would get converted into a string with all the fields
        concatenated
                together, and space-padded to their full lengths.


            I think an example is needed. I was thinking you wanted the
        field
            values transformed, but the below seems to indicate
        something different.

        No transformation is needed, except for padding the fields out
        to their
        maximum lengths.  So for example with these values

        ('AA','1243','20160801','2','1','1',37,24)

        I need a string created that looks like this:

        'AA 1243      201608012113724'

        I have a whole bunch of views that I need to do this for, and am
        hoping
        to avoid coding something specific for each one.


    I can do it relatively easy in plpythonu:

    production=# \d str_test
               Table "history.str_test"
          Column       |     Type      | Modifiers
    -------------------+---------------+-----------
     reporting_unit_id | character(3)  |
     case_id           | character(10) |
     event_date        | character(8)  |

    production=# insert into str_test values ('1', '1234', '09/07/16');
    INSERT 0 1


    DO
    $$
    rs =  plpy.execute("SELECT * FROM str_test", 1)
    cols = rs.colnames()
    plpy.notice(rs.colnames())
    str_out = ""
    for col in cols:
        str_out += str(rs[0][col])
    plpy.notice(str_out)
    $$ LANGUAGE plpythonu;

    NOTICE:  ['reporting_unit_id', 'case_id', 'event_date']
    CONTEXT:  PL/Python anonymous code block
    NOTICE:  1  1234      09/07/16
    CONTEXT:  PL/Python anonymous code block
    DO

Yeah, that and a trip to the information schema to pad out the fields
would get me the string I need.  But I was hoping to be able to do this

Well the above has the padding already there, though that assumes char(x) fields.

without having the function select the individual record.  Ideally:

SELECT my_cat(ebh_gain) FROM ebh_gain;

So do you want one record to be converted at a time or many?

or, at least somewhat more realistically:

SELECT my_cat(ebh_gain,'ebh_gain') FROM ebh_gain;

I know TCL and probably Python and others can work with a record as a
trigger function.  But TCL doesn't seem to accept a record as an
argument.  Can any of the other languages that could also accomplish
this function? Or some other way? Thanks.

--
Adrian Klaver
adrian.klaver@aklaver.com