I need to migrate SQL queries written for MS SQL Server 2005 to Postgres 9.1.
What is the best way to substitute for
dbo.GetCitizenRecModified(Citizen, LastName, FirstName, MiddleName,
BirthYear, BirthMonth, BirthDay, ..... ) -- lots of params
In Postgres 9.3 or later use a
SELECT v.col_a, v.col_b, f.* -- no parentheses here, f is a table alias FROM v_citizenversions v LEFT JOIN LATERAL f_citizen_rec_modified(v.col1, v.col2) f ON true WHERE f.col_c = _col_c;
LEFT JOIN LATERAL ... ON true?
For older versions, there is a very simple way to accomplish what I think you are trying to with a set-returning function (
RETURNS TABLE or
RETURNS SETOF record OR
SELECT *, (f_citizen_rec_modified(col1, col2)).* FROM v_citizenversions v
The function computes values once for every row of the outer query. If the function returns multiple rows, resulting rows are multiplied accordingly. All parentheses are syntactically required to decompose a row type. The table function could look something like this:
CREATE OR REPLACE FUNCTION f_citizen_rec_modified(_col1 int, _col2 text) RETURNS TABLE(col_c integer, col_d text) AS $func$ SELECT s.col_c, s.col_d FROM some_tbl s WHERE s.col_a = $1 AND s.col_b = $2 $func$ LANGUAGE sql;
You need to wrap this in a subquery or CTE if you want to apply a
WHERE clause because the columns are not visible on the same level. (And it's better for performance anyway, because you prevent repeated evaluation for every output column of the function):
SELECT col_a, col_b, (f_row).* FROM ( SELECT col_a, col_b, f_citizen_rec_modified(col1, col2) AS f_row FROM v_citizenversions v ) x WHERE (f_row).col_c = _col_c;
There are several other ways to do this or something similar. It all depends on what you want exactly.