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Postgres sync engine. Sync little subsets of your Postgres data into local apps and services.

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electric lib electric shapes shape subset.ex
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lib/electric/shapes/shape/subset.ex 

defmodule Electric.Shapes.Shape.Subset do

  alias Electric.Postgres.Inspector

  alias Electric.Replication.Eval.Env

  alias Electric.Replication.Eval.Parser

  alias Electric.Shapes.Shape.Validators



  defstruct [

    :order_by,

    :limit,

    :offset,

    :where

  ]



  @schema_options [

                    order_by: [type: :string],

                    limit: [type: :pos_integer],

                    offset: [type: :non_neg_integer],

                    where: [type: :string],

                    params: [type: {:map, :string, :string}, default: %{}]

                  ]

                  |> NimbleOptions.new!()



  def new(shape, fields, opts) do

    inspector = Access.fetch!(opts, :inspector)



    with {:ok, fields} <- NimbleOptions.validate(Map.new(fields), @schema_options),

         {:ok, columns} <- load_column_info(shape, inspector),

         :ok <- validate_order_by(fields[:order_by], columns),

         refs = Inspector.columns_to_expr(columns),

         {:ok, where} <- validate_where_clause(fields[:where], fields[:params], refs) do

      {:ok,

       %__MODULE__{

         order_by: fields[:order_by],

         limit: fields[:limit],

         offset: fields[:offset],

         where: where

       }}

    else

      {:error, %NimbleOptions.ValidationError{message: reason, key: key}} ->

        {:error, {key, reason}}



      {:error, reason} ->

        {:error, reason}

    end

  end



  defp load_column_info(%{root_table_id: table_oid, root_table: table}, inspector) do

    case Inspector.load_column_info(table_oid, inspector) do

      :table_not_found ->

        {:error,

         {:order_by,

          "Table #{Electric.Utils.inspect_relation(table)} does not exist. " <>

            "If the table name contains capitals or special characters you must quote it."}}



      {:ok, columns} ->

        {:ok, columns}

    end

  end



  defp validate_order_by(nil, _columns), do: :ok



  defp validate_order_by(order_by, columns) do

    case Parser.validate_order_by(order_by, columns) do

      :ok -> :ok

      {:error, reason} -> {:error, {:order_by, reason}}

    end

  end



  defp validate_where_clause(nil, _params, _refs), do: {:ok, nil}



  defp validate_where_clause(where, params, refs) do

    # Use an env with allow_enums: true to allow enum types in WHERE clauses for subsets.

    # Enum values are validated by Postgres at query time rather than during parsing.

    env = %{Env.new() | allow_enums: true}



    with {:ok, where} <- Parser.parse_query(where),

         {:ok, subqueries} <- Parser.extract_subqueries(where),

         :ok <- assert_no_subqueries(subqueries),

         :ok <- Validators.validate_parameters(params),

         {:ok, where} <- Parser.validate_where_ast(where, params: params, refs: refs, env: env),

         {:ok, where} <- Validators.validate_where_return_type(where) do

      {:ok, where}

    else

      {:error, {part, reason}} -> {:error, {part, reason}}

      {:error, reason} -> {:error, {:where, reason}}

    end

  end



  defp assert_no_subqueries([]), do: :ok

  defp assert_no_subqueries(_), do: {:error, "Subqueries are not allowed in subsets"}

end