... none of which require any extensions to the core type system.
AFAICS this could easily be implemented as a user-defined type, along the lines of
CREATE TYPE measurement AS (value double, units text);
and if you want to constrain a particular column to contain only one value of units, use CHECK.
The argument that we should extend the type system for this would become
a lot more credible if there were a widely-used extension in existence
for it to prove that there's sufficient demand.
I have begining to put all the SI unit in a table. I am writing the function to check the unit in a standard way. I plan to use the user-defined type proposed by Tom Lane. The check are done at execution time.
But I object that what I am doing is just a proof of concept and not the right thing to do.
I do not want for each column and each row to store the value and the unit.
I do want to put the unit in the definition of the column and the check on the parser before any execution.
Cordialement, Jean-Gérard Pailloncy
---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
