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exosql
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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/builtins.ex
require Logger
defmodule ExoSQL.Builtins do
@moduledoc """
Builtin functions.
There are two categories, normal functions and aggregate functions. Aggregate
functions receive as first parameter a ExoSQL.Result with a full table,
and the rest of parameters are the function calling parameters, unsolved.
These expressions must be first simplified with
`ExoSQL.executor.simplify_expr_columns` and then executed on the rows with
`ExoSQL.Expr.run_expr`.
"""
import ExoSQL.Utils, only: [to_number: 1, to_float: 1]
def round(n, r) do
{:ok, n} = to_float(n)
{:ok, r} = to_number(r)
Float.round(n, r)
end
def concat(a, b) do
a = to_string(a)
b = to_string(b)
a <> b
end
def not_(a) do
not bool(a)
end
def bool(nil), do: false
def bool(0), do: false
def bool(""), do: false
def bool(false), do: false
def bool(_), do: true
def lower(s), do: String.downcase(s)
def upper(s), do: String.upcase(s)
def to_string_(%DateTime{} = d), do: DateTime.to_iso8601(d)
def to_string_(s), do: to_string(s)
def now(), do: DateTime.utc_now()
def to_datetime(other), do: ExoSQL.DateTime.to_datetime(other)
def to_timestamp(%DateTime{} = d), do: DateTime.to_unix(d)
def substr(str, skip, len) do
{:ok, skip} = to_number(skip)
{:ok, len} = to_number(len)
if len < 0 do
String.slice(str, skip, String.length(str) + len)
else
String.slice(str, skip, skip + len)
end
end
@doc ~S"""
Convert datetime to string.
If no format is given, it is as to_string, which returns the ISO 8601.
Format allows these substitutions (subset from SQLITE):
%d day of month: 00
%H hour: 00-24
%m month: 01-12
%M minute: 00-59
%s seconds since 1970-01-01
%S seconds: 00-59
%Y year: 0000-9999
%i ISO 8601 format
%% %
"""
def strftime(%DateTime{} = d), do: to_string_(d)
def strftime(%DateTime{} = d, format), do: ExoSQL.DateTime.strftime(d, format)
def strftime(other, format), do: strftime(to_datetime(other), format)
### Aggregate functions
def is_aggregate("count"), do: true
def is_aggregate("avg"), do: true
def is_aggregate("sum"), do: true
def is_aggregate(_other), do: false
def count(data, _) do
# Logger.debug("Count #{inspect data}")
Enum.count(data.rows)
end
def avg(data, expr) do
# Logger.debug("Avg of #{inspect data} by #{inspect expr}")
sum(data, expr) / count(data, nil)
end
def sum(data, expr) do
# Logger.debug("Sum of #{inspect data} by #{inspect expr}")
expr = ExoSQL.Executor.simplify_expr_columns(expr, data.columns, nil)
# Logger.debug("Simplified expression #{inspect expr}")
Enum.reduce(data.rows, 0, fn row, acc ->
n = ExoSQL.Expr.run_expr(expr, row)
{:ok, n} = ExoSQL.Utils.to_number(n)
acc + n
end)
end
end