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lib/exd/query_runner/planner.ex
defmodule Exd.Runner.Planner do
@moduledoc """
Plans the execution of a query
"""
alias Exd.Query
alias Exd.Runner.{From, Join, Where, Select, Into, Commit}
@doc """
Plan query flow
"""
@spec plan(Query.t()) :: Flow.t()
def plan(%Query{} = query) do
query
|> plan_from
|> plan_joins(query)
|> plan_wheres(query)
|> plan_select(query)
|> plan_into(query)
end
defp plan_from(%Query{from: {namespace, specable, opts}}) do
From.from(namespace, specable, opts)
end
defp plan_joins(flow, %Query{joins: joins} = _query) do
joins
|> Enum.reduce(flow, fn %{from: {namespace, specable, opts}} = _join, flow ->
Join.join(flow, namespace, specable, opts)
end)
end
defp plan_wheres(flow, %Query{where: wheres} = _query) do
wheres
|> Enum.reduce(flow, fn {field, relation, value} = _where, flow ->
Where.where(flow, field, relation, value)
end)
end
defp plan_select(flow, %Query{select: nil} = _query), do: flow
defp plan_select(flow, %Query{select: select} = _query) do
Select.select(flow, select)
end
defp plan_into(flow, %Query{into: nil} = _query), do: flow
defp plan_into(flow, %Query{into: {namespace, sink}}) do
Into.into(flow, sink)
end
end