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Postgres sync engine. Sync little subsets of your Postgres data into local apps and services.
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lib/electric/replication/eval/expr.ex
defmodule Electric.Replication.Eval.Expr do
@moduledoc """
Parsed expression, available for evaluation using the runner
"""
alias Electric.Replication.Eval.Parser
alias Electric.Replication.Eval.Env
defstruct [:query, :eval, :used_refs, :returns]
@type used_refs :: %{required([String.t(), ...]) => Env.pg_type()}
@type t() :: %__MODULE__{
query: String.t(),
eval: term(),
used_refs: used_refs(),
returns: Env.pg_type()
}
@doc """
Returns a flat list of all used refs used in the expression
that point to the current table
## Examples
iex> used_refs = %{["id"] => :int8, ["created_at"] => :timestamp}
iex> unqualified_refs(%Expr{query: "id = 1", used_refs: used_refs})
["created_at", "id"]
iex> used_refs = %{["id"] => :int8, ["potato", "created_at"] => :timestamp}
iex> unqualified_refs(%Expr{query: "id = 1", used_refs: used_refs, returns: :int8})
["id"]
"""
@spec unqualified_refs(t()) :: [String.t()]
def unqualified_refs(%__MODULE__{used_refs: used_refs}) do
used_refs
# Keep only used refs that are pointing to current table
|> Enum.filter(&match?({[_], _}, &1))
|> Enum.map(fn {[key], _} -> key end)
end
@doc false
@spec to_json_safe(t()) :: map()
def to_json_safe(%__MODULE__{query: query, used_refs: used_refs}) do
%{
version: 1,
query: query,
used_refs: Enum.map(used_refs, fn {k, v} -> [k, json_safe_type(v)] end)
}
end
defp json_safe_type({:array, type}), do: [:array, json_safe_type(type)]
defp json_safe_type({:row, types}), do: [:row, Enum.map(types, &json_safe_type/1)]
defp json_safe_type({:internal, type}), do: [:internal, json_safe_type(type)]
defp json_safe_type({:enum, type}), do: [:enum, json_safe_type(type)]
defp json_safe_type(type), do: type
@doc false
@spec from_json_safe(map()) :: {:ok, t()} | {:error, String.t()}
def from_json_safe(map, sublink_queries \\ %{})
def from_json_safe(
%{"version" => 1, "query" => query, "used_refs" => refs},
sublink_queries
) do
refs =
Map.new(refs, fn [k, v] -> {k, type_from_json_safe(v)} end)
Parser.parse_and_validate_expression(query, refs: refs, sublink_queries: sublink_queries)
end
def from_json_safe(_, _),
do: {:error, "Incorrect serialized format: keys must be `version`, `query`, `used_refs`"}
defp type_from_json_safe(["array", type]), do: {:array, type_from_json_safe(type)}
defp type_from_json_safe(["row", types]), do: {:row, Enum.map(types, &type_from_json_safe/1)}
defp type_from_json_safe(["internal", type]), do: {:internal, type_from_json_safe(type)}
defp type_from_json_safe(["enum", type]), do: {:enum, type_from_json_safe(type)}
defp type_from_json_safe(type) when is_binary(type), do: String.to_existing_atom(type)
@doc """
Wrap a parser part (Const, Ref, Func, Array, RowExpr) in an Expr struct, so that it can be evaluated on it's own.
This is used when a subtree of our AST needs to be made evaluatable on it's own inside Electric. The `query` field
is not needed in that context, it's used when going back to postgres, so we don't bother calculating it.
"""
def wrap_parser_part(expr) do
%__MODULE__{
query: "This should not be executed on the database",
eval: expr,
used_refs: Parser.find_refs(expr),
returns: expr.type
}
end
defimpl Electric.Shapes.Shape.Comparable do
def comparable(%Electric.Replication.Eval.Expr{} = expr) do
{:eval_expr, expr.query, expr.returns}
end
end
end
defimpl Jason.Encoder, for: Electric.Replication.Eval.Expr do
def encode(expr, opts) do
expr
|> Electric.Replication.Eval.Expr.to_json_safe()
|> Jason.Encode.map(opts)
end
end