Troublesome conversion of plain PostgreSQL query to Slick query - postgresql

Question

I have a plain PostgreSQL query I'm having trouble translating into slick query. I go stuck in syntax soup when using groupBy clause.
SELECT u.id AS investor_id,
u.account_type,
i.first_name,
issuer_user.display_name AS issuer_name,
p.legal_name AS product_name,
v.investment_date,
iaa.as_of AS CCO_approval_date,
v.starting_investment_amount,
v.maturity_date,
v.product_interest_rate,
v.product_term_length,
i.user_information_id,
v.id AS investment_id
FROM investors u
JOIN
( SELECT ipi.investor_id,
ipi.first_name,
ipi.user_information_id
FROM investor_personal_information ipi
JOIN
( SELECT investor_id,
MAX(id) AS Max_Id
FROM investor_personal_information
GROUP BY investor_id ) M ON ipi.investor_id = m.investor_id
AND ipi.id = m.Max_Id ) i ON u.id = i.investor_id
JOIN investments v ON u.id = v.investor_id
JOIN sub_products AS sp ON v.sub_product_id = sp.id
JOIN products AS p ON p.id = sp.product_id
JOIN company AS c ON c.id = p.company_id
JOIN issuers AS issuer ON issuer.id = c.issuer_id
JOIN users AS issuer_user ON issuer.owner = issuer_user.id
JOIN investment_admin_approvals AS iaa ON iaa.investment_id = v.id
ORDER BY i.first_name DESC;
I've started writing it
val query = {
val investorInfoQuery = (for {
i <- InvestorPersonalInformation
} yield (i)).groupBy {
_.investorId
}.map {
case (id, rest) => {
id -> rest.map(_.id).max
}
}
}
I know I've to create base queries into one big query and apply joins on them separately. Can anybody help guiding me or providing me some examples? Slick is hard.

Answer 1

Looks pretty simple to write. I am not going to help you write the whole query, I will just give you an example which you can follow to wrtie your query.
Lets say you had following structure and respective table queries defined as employees, emplayeePackages and employeeSalaryCredits
case class Employee(id: String, name: String)
case class EmployeePackage(id: String, employeeId: String, baseSalary: Double)
case class EmployeeSalaryCredit(id: String, employeeId: String, salaryCredited: Double, date: ZonedDateTime)
Now lets say you want all salary credits for all employees with employee's id, employee's name, base salary, actual credited salary and date of salary credit then your query will look like
val queryExample = employees
.join(employeePackages)
.on({ case (e, ep ) => e.id === ep.employeeId })
.join(employeeSalaryCredits)
.on({ case ((e, ep), esc) => e.id === esc.employeeId })
.map({ case ((e, ep), esc) =>
(e.id, e.name, ep.baseSalary, esc.salaryCredited, esc.date)
})