CTable: Columnar Compressed Table for Blosc2#614
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FrancescAlted merged 22 commits intoBlosc:ctable4from Apr 8, 2026
Merged
CTable: Columnar Compressed Table for Blosc2#614FrancescAlted merged 22 commits intoBlosc:ctable4from
FrancescAlted merged 22 commits intoBlosc:ctable4from
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Introduce CTable, a new columnar table class for efficient in-memory data storage using Blosc2 as the underlying compression engine. Each column is represented as a Column object wrapping a blosc2.NDArray with typed, compressed storage. Building on top of blosc2's existing infrastructure, CTable supports append, iteration and column-based queries. This is an early-stage (beta) implementation; the table is always fully loaded in memory. New files: - src/blosc2/ctable.py: CTable and Column class definitions - tests/ctable/: unit tests covering construction, slicing, deletion, compaction and row logic - bench/ctable/: benchmarks comparing CTable against pandas
Add CTable, a columnar in-memory table built on top of blosc2
- Add schema.py with spec primitives: int8/16/32/64, uint8/16/32/64,
float32/64, bool, complex64/128, string, bytes — sharing a _NumericSpec
mixin to avoid boilerplate
- Add schema_compiler.py: compile_schema(), CompiledSchema/Column/Config,
schema_to_dict() / schema_from_dict() for persistence groundwork
- Export all spec types and field() from blosc2 namespace
Validation:
- Add schema_validation.py: Pydantic-backed row validation for append(),
cached per schema, re-raised as plain ValueError
- Add schema_vectorized.py: vectorized NumPy constraint checks for extend(),
using np.char.str_len() for string/bytes columns
- validate= per-call override on extend() (None inherits table default)
CTable refactor:
- Constructor accepts dataclass schemas; legacy Pydantic adapter kept
- Schema introspection: table.schema, column_schema(), schema_dict()
- _last_pos cache eliminates backward chunk scan on every append/extend
- _grow() shared resize helper; delete() writes back in-place without
creating a new array; _n_rows updated by subtraction not count_nonzero
- head() and tail() unified through _find_physical_index()
Tests and docs:
- 135 tests across 10 test files, all passing
- plans/ctable-implementation-log.md and ctable-user-guide.md added
- Benchmarks: bench_validation.py and bench_append_regression.py
…QoL)
Persistency:
- FileTableStorage backend: disk layout _meta.b2frame / _valid_rows.b2nd / _cols/<name>.b2nd
- CTable(Row, urlpath=..., mode="w"/"a"/"r"), CTable.open(), CTable.save(), CTable.load()
- Read-only mode blocks all writes; save() always writes compacted rows
Column aggregates: sum, min, max, mean, std, any, all (chunk-aware via iter_chunks)
Column utilities: unique(), value_counts(), assign(), boolean mask __getitem__/__setitem__
Schema mutations: add_column (fills default for existing rows), drop_column, rename_column
- All three update schema, handle disk files, and block on views
View mutability model fix:
- Views allow value writes (assign, __setitem__) — only structural mutations are blocked
- _read_only=True reserved for mode="r" disk tables; base is not None guards structural ops
QoL: __str__ pandas-style, __repr__, cbytes/nbytes, sample(n), Column.iter_chunks(size)
Tests: 258 tests, ~5s — new test_persistency.py (33), test_schema_mutations.py (41),
expanded test_column.py; optimized helpers to use to_numpy() instead of row[i]
…QoL)
Persistency:
- FileTableStorage backend: disk layout _meta.b2frame / _valid_rows.b2nd / _cols/<name>.b2nd
- CTable(Row, urlpath=..., mode="w"/"a"/"r"), CTable.open(), CTable.save(), CTable.load()
- Read-only mode blocks all writes; save() always writes compacted rows
Column aggregates: sum, min, max, mean, std, any, all (chunk-aware via iter_chunks)
Column utilities: unique(), value_counts(), assign(), boolean mask __getitem__/__setitem__
Schema mutations: add_column (fills default for existing rows), drop_column, rename_column
- All three update schema, handle disk files, and block on views
View mutability model fix:
- Views allow value writes (assign, __setitem__) — only structural mutations are blocked
- _read_only=True reserved for mode="r" disk tables; base is not None guards structural ops
QoL: __str__ pandas-style, __repr__, cbytes/nbytes, sample(n), Column.iter_chunks(size)
Tests: 258 tests, ~5s — new test_persistency.py (33), test_schema_mutations.py (41),
expanded test_column.py; optimized helpers to use to_numpy() instead of row[i]
Arrow compatibility Examples Tutorial
FrancescAlted
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CTable: Columnar Compressed Table for Blosc2
This PR introduces CTable, a typed columnar table backed by blosc2.NDArray per column, with full
schema validation, persistence, and interoperability.
Schema layer
complex64/128, string, bytes
Core table operations
Persistence
Interoperability
column, no row-level overhead
deletions
Tests & examples
interop, CSV interop
dataset as the running example