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Universal SQL engine for Elixir. This library implements the SQL logic to perform queries on user provided databases using a simple interface based on Foreign Data Wrappers from PostgreSQL.
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lib/expr.ex
require Logger
defmodule ExoSQL.Expr do
@moduledoc """
Expression executor.
Requires a simplified expression from `simplify_expr_columns` that converts
columns names to column positions, and then use as:
```
iex> row = [1,2,3,4,5]
iex> expr = {:op, {"*", {:column, 1}, {:column, 2}}}
iex> ExoSQL.Expr.run_expr(expr, row)
6
```
"""
import ExoSQL.Utils, only: [to_number: 1]
def run_expr({:op, {"and", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
r1 && r2
end
def run_expr({:op, {"AND", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
r1 && r2
end
def run_expr({:op, {"or", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
r1 || r2
end
def run_expr({:op, {"OR", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
r1 || r2
end
def run_expr({:op, {"=", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
{r1, r2} = match_types(r1, r2)
r1 == r2
end
def run_expr({:op, {">", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
{r1, r2} = match_types(r1, r2)
case {r1, r2} do
{%DateTime{}, %DateTime{}} ->
DateTime.compare(r1, r2) == :gt
_ ->
with {:ok, n1} <- to_number(r1),
{:ok, n2} <- to_number(r2) do
n1 > n2
else
{:error, _} ->
r1 > r2
end
end
end
def run_expr({:op, {">=", op1, op2}}, cur) do
r1 = run_expr(op1, cur)
r2 = run_expr(op2, cur)
{r1, r2} = match_types(r1, r2)
case {r1, r2} do
{%DateTime{}, %DateTime{}} ->
DateTime.compare(r1, r2) == :eq
{a, b} ->
with {:ok, n1} <- to_number(r1),
{:ok, n2} <- to_number(r2) do
n1 >= n2
else
{:error, _} ->
a >= b
end
end
end
def run_expr({:op, {"==", op1, op2}}, cur), do: run_expr({:op, {"=", op1, op2}}, cur)
def run_expr({:op, {"!=", op1, op2}}, cur), do: not run_expr({:op, {"=", op1, op2}}, cur)
def run_expr({:op, {"<", op1, op2}}, cur), do: not run_expr({:op, {">=", op1, op2}}, cur)
def run_expr({:op, {"<=", op1, op2}}, cur), do: not run_expr({:op, {">", op1, op2}}, cur)
def run_expr({:op, {"*", op1, op2}}, cur) do
{:ok, n1} = to_number(run_expr(op1, cur))
{:ok, n2} = to_number(run_expr(op2, cur))
n1 * n2
end
def run_expr({:op, {"/", op1, op2}}, cur) do
{:ok, n1} = to_number(run_expr(op1, cur))
{:ok, n2} = to_number(run_expr(op2, cur))
n1 / n2
end
def run_expr({:op, {"+", op1, op2}}, cur) do
{:ok, n1} = to_number(run_expr(op1, cur))
{:ok, n2} = to_number(run_expr(op2, cur))
n1 + n2
end
def run_expr({:op, {"-", op1, op2}}, cur) do
{:ok, n1} = to_number(run_expr(op1, cur))
{:ok, n2} = to_number(run_expr(op2, cur))
n1 - n2
end
def run_expr({:op, {"||", op1, op2}}, cur) do
s1 = to_string(run_expr(op1, cur))
s2 = to_string(run_expr(op2, cur))
s1<>s2
end
def run_expr({:fn, {fun, exprs}}, cur) do
params = for e <- exprs, do: run_expr(e, cur)
ExoSQL.Builtins.call_function(fun, params)
end
def run_expr({:pass, val}, _cur), do: val
def run_expr({:lit, val}, _cur), do: val
def run_expr({:column, n}, cur) when is_number(n) do
Enum.at(cur, n)
end
@doc """
Try to return matching types.
* If any is datetime, return datetimes
* If any is number, return numbers
* Otherwise, as is
"""
def match_types(a, b) do
case {a, b} do
{t1, t2} when is_number(t1) and is_number(t2) ->
{a, b}
{%DateTime{}, _} ->
{a, ExoSQL.Builtins.to_datetime(b)}
{_, %DateTime{}} ->
{ExoSQL.Builtins.to_datetime(a), b}
{t1, _} when is_number(t1) ->
{:ok, t2} = to_number(b)
{t1, t2}
{_, t2} when is_number(t2) ->
{:ok, t1} = to_number(a)
{t1, t2}
_other ->
{a, b}
end
end
end