Crate datafusion_functions_aggregate

Aggregate Function packages for DataFusion.

This crate contains a collection of various aggregate function packages for DataFusion, implemented using the extension API. Users may wish to control which functions are available to control the binary size of their application as well as use dialect specific implementations of functions (e.g. Spark vs Postgres)

Each package is implemented as a separate module, activated by a feature flag.

Available Packages

See the list of modules in this crate for available packages.

Using A Package

You can register all functions in all packages using the register_all function.

Each package also exports an expr_fn submodule to help create Exprs that invoke functions using a fluent style. For example:

Implementing A New Package

To add a new package to this crate, you should follow the model of existing packages. The high level steps are:

1. Create a new module with the appropriate AggregateUDF implementations.

2. Use the macros in macros to create standard entry points.

3. Add a new feature to Cargo.toml, with any optional dependencies

4. Use the make_package! macro to expose the module when the feature is enabled.

Modules

• approx_distinct
  Defines physical expressions that can evaluated at runtime during query execution
• approx_median
  Defines physical expressions for APPROX_MEDIAN that can be evaluated MEDIAN at runtime during query execution
• approx_percentile_cont
• approx_percentile_cont_with_weight
• array_agg
  ARRAY_AGG aggregate implementation: ArrayAgg
• average
  Defines Avg & Mean aggregate & accumulators
• bit_and_or_xor
  Defines BitAnd, BitOr, BitXor and BitXor DISTINCT aggregate accumulators
• bool_and_or
  Defines physical expressions that can evaluated at runtime during query execution
• correlation
  Correlation: correlation sample aggregations.
• count
• covariance
  CovarianceSample: covariance sample aggregations.
• expr_fn
  Fluent-style API for creating Exprs
• first_last
  Defines the FIRST_VALUE/LAST_VALUE aggregations.
• grouping
  Defines physical expressions that can evaluated at runtime during query execution
• hyperloglog
  HyperLogLog
• macros
• median
• min_max
  Max and MaxAccumulator accumulator for the max function Min and MinAccumulator accumulator for the min function
• nth_value
  Defines NTH_VALUE aggregate expression which may specify ordering requirement that can evaluated at runtime during query execution
• regr
  Defines physical expressions that can evaluated at runtime during query execution
• stddev
  Defines physical expressions that can evaluated at runtime during query execution
• string_agg
  StringAgg accumulator for the string_agg function
• sum
  Defines SUM and SUM DISTINCT aggregate accumulators
• variance
  VarianceSample: variance sample aggregations. VariancePopulation: variance population aggregations.

Functions

• all_default_aggregate_functions
  Returns all default aggregate functions
• register_all
  Registers all enabled packages with a FunctionRegistry