Blosc/python-blosc2

[Tutorial] CTable copy() with reblocking and recompression

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#644 opened on Jun 2, 2026

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Description

The CTable.copy() method gained new chunks=, blocks=, and cparams= overrides in this release, but there is no tutorial showing when and why you would use them. There is a standalone example at examples/ctable/copying.py, but no notebook integrated into the tutorial sequence.

Suggested work: Add a notebook 16.ctable-copy.ipynb to doc/getting_started/tutorials/ covering:

  • Basic in-memory and persistent copy
  • Reblocking: how block size affects SUMMARY index granularity and query pruning
  • Recompression: switching codecs (ZSTD → LZ4) and what to expect on size vs speed
  • Copying a projected view (select().copy()) to persist a column subset

Contributor guide

Research direction
Read the existing copy() documentation and example at examples/ctable/copying.py. Study the concepts of reblocking and recompression in blosc2 to understand how to demonstrate them in a tutorial notebook.
Tech stack
python
Domain
documentation
Issue type
Documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Python
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75