dream_postgres/query

Database query helpers

Simple utilities for extracting rows from Pog query results. Use these after executing database queries to get your data out cleanly.

Example

import dream_postgres/query

case sql.get_user(db, id) |> query.first_row() {
  Ok(user) -> Ok(decode_user(user))
  Error(query.NotFound) -> Error("User not found")
  Error(query.DatabaseError) -> Error("Database error")
}

Types

QueryError

</>

Query error types

Simplified error types for query results. Converts Pog’s QueryError into a simpler two-variant type for easier error handling.

Variants

NotFound: Query succeeded but returned no rows
DatabaseError: Query failed (connection error, SQL error, etc.)

pub type QueryError {
  NotFound
  DatabaseError
}

Constructors

```
NotFound
```
```
DatabaseError
```

Values

all_rows

</>

pub fn all_rows(
  result: Result(pog.Returned(row), pog.QueryError),
) -> Result(List(row), QueryError)

Extract all rows from a query result

Extracts all rows from a Pog query result. This is useful for queries that return multiple rows (e.g., “list all” queries).

Returns an empty list if the query succeeded but found no rows, or DatabaseError if the query itself failed.

Parameters

result: The result from a Pog query execution

Returns

Ok(List(row)): All rows (may be empty)
Error(DatabaseError): Query failed (connection error, SQL error, etc.)

Example

import dream_postgres/query
import user/sql

case sql.list_users(db) |> query.all_rows() {
  Ok(users) -> user_view.respond_list(users)
  Error(query.DatabaseError) -> error_response()
}

first_row

</>

pub fn first_row(
  result: Result(pog.Returned(row), pog.QueryError),
) -> Result(row, QueryError)

Extract the first row from a query result

Extracts the first row from a Pog query result. This is useful for queries that should return exactly one row (e.g., “get by ID” queries).

Returns NotFound if the query succeeded but returned no rows, or DatabaseError if the query itself failed.

Parameters

result: The result from a Pog query execution

Returns

Ok(row): First row found
Error(NotFound): Query succeeded but no rows returned
Error(DatabaseError): Query failed (connection error, SQL error, etc.)

Example

import dream_postgres/query
import user/sql

case sql.get_user(db, id) |> query.first_row() {
  Ok(user) -> user_view.respond(user)
  Error(query.NotFound) -> not_found_response()
  Error(query.DatabaseError) -> error_response()
}