Crate fp_join 

Merge / join engine for frankenpandas — implements pandas-shape pd.merge / pd.merge_ordered / pd.merge_asof / Series.join for DataFrame and Series operands.

Why a separate crate

Joins have substantial machinery — hash-build phases, asof search, validate-mode integrity checks, bumpalo-backed intermediate buffers — that doesn’t belong inside fp-frame’s row/column primitives. fp-join layers on top of fp-columnar / fp-index / fp-frame and exposes a merge surface matching the pandas API shape.

Top-level entry points

• join_series / join_series_with_options: pandas Series.join(other, how=...). Returns a JoinedSeries.
• merge_dataframes: index-on-index merge (pandas df.merge(other, left_index=True, right_index=True)).
• merge_dataframes_on / merge_dataframes_on_with / merge_dataframes_on_with_options: column-key merge (pd.merge(left, right, on=...)). Returns a MergedDataFrame.
• merge_ordered: pandas pd.merge_ordered(left, right, on=...) — preserves ordering for time-series merges.
• merge_asof / merge_asof_with_options: pandas pd.merge_asof(left, right, on=..., direction=...) for nearest-key time-aware merges. AsofDirection / MergeAsofOptions tune the search.

DataFrame extension trait

DataFrameMergeExt adds df.merge(...) / df.join(...) method-style entry points so callers get fluent chaining after use fp_join::DataFrameMergeExt;.

Tunables

• JoinType: Inner / Left / Right / Outer / Cross.
• MergeValidateMode: pandas validate='one_to_one' | 'one_to_many' | 'many_to_one' | 'many_to_many' integrity check before producing the result.
• JoinExecutionOptions / MergeExecutionOptions: per-call knobs (suffixes for overlapping columns, indicator column, sort policy, …).

Error reporting

JoinError enumerates the failure modes (key column mismatch, validate-mode violation, dtype mismatch on key column, …).

Cross-crate relationships

• fp-columnar (Column, ColumnError) for column storage operations.
• fp-frame for the DataFrame / Series value types.
• fp-index for row alignment plans + label types.
• fp-types for the underlying scalar machinery.

Structs

JoinExecutionOptions

JoinedSeries

MergeAsofOptions

Options for asof merge operations.

MergeExecutionOptions

MergedDataFrame

Result of a DataFrame merge operation.

Enums

AsofDirection

Direction for asof merge matching.

JoinError

JoinType

MergeValidateMode

Constants

DEFAULT_ARENA_BUDGET_BYTES

Traits

DataFrameMergeExt

Extension trait adding .merge() and .join() instance methods to DataFrame.

Functions

join_series

join_series_with_options

merge_asof

Perform an asof merge between two DataFrames.

merge_asof_with_options

Perform an asof merge between two DataFrames with additional options.

merge_dataframes

Merge two DataFrames on a single key column.

merge_dataframes_on

Merge two DataFrames on one or more key columns with identical key names.

merge_dataframes_on_with

Merge two DataFrames on one or more key columns.

merge_dataframes_on_with_options

Merge two DataFrames on one or more key columns with execution options.

merge_ordered

Perform an ordered merge of two DataFrames.