Datasource Statements

Datasource statements are used to both define sources of data - the roots of a model - and to define targets for writing data back out.

Syntax

"datasource" IDENTIFIER "(" column_assignment_list ")" grain_clause? (address | query)

Identifier

The named alias of the datasource is used if the datasource is referenced in a persist, validate, or publish statement.

Column Assignment List

The column assignment list contains the binding of physical columns on the datasource to concepts.

A binding can take one of 3 forms:

customers(
    # a bare binding represents a mapping from "id" on the table to "id" as a concept
    id,
    # a colon binding maps "name" on the table to "user_name" as a concept
    name: user_name,
    # a function binding can reference a prior filed
    UPPER(name): upper_name,
    # a rawsql binding can reference a sql expression
)

Grain Clause

The grain clause defines unique identifiers for rows in the table. (A primary key, or composite primary key)

Address/Query

A datasource can either come from a table

address database.my_fun_table

or from a query

query '''
select fun_data
'''

Tips

Query sources are very useful for experimentation, injecting in values, and bespoke database SQL syntax

Example

import std.money;
import nation as nation;
key id int;
property id.name string;
property id.address string;
property id.phone string;
property id.account_balance float::usd;
property id.market_segment string; # Capitalized; one of BUILDING | FURNITURE | MACHINERY | AUTOMOBILE | HOUSEHOLD
property id.comment string;
datasource customers (
    c_custkey:id,
    c_name:name,
    c_address:address,
    c_nationkey:nation.id,
    c_phone:phone,
    c_acctbal:account_balance,
    c_mktsegment:market_segment,
    c_comment:comment
)
grain (id)
address memory.customer;