Selecto.TypeSystem (Selecto v0.3.8)
Type inference and coercion system for Selecto SQL expressions.
This module provides:
- Type inference for expressions (fields, functions, literals, complex expressions)
- Type compatibility checking for comparisons and set operations
- Type coercion rules for implicit type conversions
- Return type determination for SQL functions and aggregates
type-categories
Type Categories
Selecto organizes SQL types into the following categories:
- Numeric:
:integer,:bigint,:smallint,:decimal,:float,:numeric - String:
:string,:text,:varchar,:char - Boolean:
:boolean - DateTime:
:date,:time,:datetime,:utc_datetime,:naive_datetime,:timestamp - JSON:
:json,:jsonb,:map - Array:
{:array, inner_type} - Binary:
:binary,:bytea - UUID:
:uuid,:binary_id - Spatial:
:geometry,:geography,:point,:polygon, etc.
usage
Usage
# Infer type of an expression
{:ok, :integer} = Selecto.TypeSystem.infer_type(selecto, {:count, "*"})
{:ok, :decimal} = Selecto.TypeSystem.infer_type(selecto, {:sum, "price"})
{:ok, :string} = Selecto.TypeSystem.infer_type(selecto, "product_name")
# Check type compatibility
true = Selecto.TypeSystem.compatible?(:integer, :decimal)
false = Selecto.TypeSystem.compatible?(:string, :boolean)
# Get coerced type for operation
{:ok, :decimal} = Selecto.TypeSystem.coerce_types(:integer, :decimal, :arithmetic)Link to this section Summary
Functions
Determine the result type when coercing two types for an operation.
Check if two types are compatible for comparisons or assignments.
Check if a type is a date/time type.
Infer the SQL type of an expression.
Infer type and return just the type (for internal use where errors are handled upstream).
Normalize Ecto types to Selecto's internal type representation.
Check if a type is numeric.
Parse a SQL type string into an atom type.
Check if a type is a string type.
Get the type category for a given SQL type.
Link to this section Types
sql_type()
@type sql_type() :: :unknown | :integer | :bigint | :smallint | :decimal | :float | :numeric | :string | :text | :varchar | :char | :boolean | :date | :time | :datetime | :utc_datetime | :naive_datetime | :timestamp | :json | :jsonb | :map | :binary | :bytea | :uuid | :binary_id | :geometry | :geography | :point | :linestring | :polygon | :multipoint | :multilinestring | :multipolygon | :geometrycollection | {:array, sql_type()}
type_category()
@type type_category() ::
:numeric
| :string
| :boolean
| :datetime
| :json
| :array
| :binary
| :uuid
| :spatial
| :unknown
Link to this section Functions
coerce_types(type1, type2, operation)
Determine the result type when coercing two types for an operation.
operation-types
Operation Types
:arithmetic- Numeric operations (+, -, *, /):comparison- Comparison operations (=, <>, <, >, etc.):concatenation- String concatenation (||):union- Set operations (UNION, INTERSECT, EXCEPT)
compatible?(type, type)
Check if two types are compatible for comparisons or assignments.
datetime_type?(type)
Check if a type is a date/time type.
infer_type(selecto, expression)
Infer the SQL type of an expression.
Returns {:ok, type} for successfully inferred types,
or {:ok, :unknown} when the type cannot be determined.
examples
Examples
iex> infer_type(selecto, "product_name")
{:ok, :string}
iex> infer_type(selecto, {:count, "*"})
{:ok, :bigint}
iex> infer_type(selecto, {:sum, "price"})
{:ok, :decimal}infer_type!(selecto, expression)
Infer type and return just the type (for internal use where errors are handled upstream).
normalize_type(type)
Normalize Ecto types to Selecto's internal type representation.
numeric_type?(type)
Check if a type is numeric.
parse_sql_type(type_str)
Parse a SQL type string into an atom type.
string_type?(type)
Check if a type is a string type.
type_category(type)
@spec type_category(sql_type()) :: type_category()
Get the type category for a given SQL type.