feat(pagination): add cursor-based pagination + client APIs #112

histrio · 2025-09-30T07:25:06Z

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codecov-commenter · 2025-09-30T07:26:15Z

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Codecov Report

❌ Patch coverage is 94.62366% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.48%. Comparing base (320ad31) to head (da5587e).

Files with missing lines	Patch %	Lines
pycouchdb/client.py	90.00%	3 Missing ⚠️
pycouchdb/pagination.py	96.42%	2 Missing ⚠️
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@@            Coverage Diff             @@
##           master     #112      +/-   ##
==========================================
+ Coverage   88.74%   89.48%   +0.73%     
==========================================
  Files           7        8       +1     
  Lines         622      713      +91     
==========================================
+ Hits          552      638      +86     
- Misses         70       75       +5

Flag	Coverage Δ
unittests	`89.48% <94.62%> (+0.73%)`	⬆️

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Copilot

Pull Request Overview

This PR adds cursor-based pagination functionality to pycouchdb, implementing both view and Mango query pagination along with client API methods. The main purpose is to provide stable, memory-efficient pagination without the pitfalls of skip-based pagination.

Key changes:

Adds a new pagination.py module with view_pages() and mango_pages() functions for cursor-based pagination
Extends the Database class with find(), view_pages(), and mango_pages() methods
Includes comprehensive test coverage for both unit and integration testing

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pycouchdb/pagination.py	Core pagination logic implementing cursor-based pagination for views and Mango queries
pycouchdb/client.py	Database class extensions adding pagination methods and Mango query support
pycouchdb/types.py	Type aliases for pagination-related types
pycouchdb/utils.py	Enhanced UTF-8 decoding with error handling
test/test_pagination.py	Unit tests for pagination functions with mocked dependencies
test/test_database.py	Unit tests for new Database methods
test/integration/test_pagination_integration.py	Comprehensive integration tests with real CouchDB
test/integration/test_integration.py	Additional integration tests for pagination functionality
docs/source/quickstart.rst	Documentation updates explaining pagination features

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

Copilot · 2025-09-30T07:26:16Z

pycouchdb/pagination.py

+        last_row = rows[page_size - 1]
+        startkey = last_row['key']
+        startkey_docid = last_row['id']
+        skip = 1  # Skip the row we used as cursor


[nitpick] The inline comment explains what skip=1 does, but it would be clearer to explain why this is necessary to avoid duplicate results in cursor-based pagination.

Suggested change

skip = 1 # Skip the row we used as cursor

skip = 1 # Skip the row used as the cursor to avoid returning it again (prevents duplicate results in cursor-based pagination)

Copilot · 2025-09-30T07:26:17Z

pycouchdb/pagination.py

+def _prepare_mango_data(selector: Dict[str, Any], params: Dict[str, Any]) -> bytes:
+    """Prepare Mango query data for HTTP request."""
+    data_dict = {
+        'selector': selector,
+        **params
+    }
+    return utils.force_bytes(json.dumps(data_dict))


The _prepare_mango_data function is defined but never used in the code. Consider removing it or adding a comment explaining its intended future use.

Suggested change

def _prepare_mango_data(selector: Dict[str, Any], params: Dict[str, Any]) -> bytes:

"""Prepare Mango query data for HTTP request."""

data_dict = {

'selector': selector,

**params

}

return utils.force_bytes(json.dumps(data_dict))

Copilot · 2025-09-30T07:26:17Z

pycouchdb/client.py

+        :param params: Additional query parameters
+        :returns: Iterator yielding lists of rows for each page
+
+        .. versionadded: 1.17


The docstring format should be .. versionadded:: 1.17 with double colons, not single colon.

Suggested change

.. versionadded: 1.17

.. versionadded:: 1.17

Copilot · 2025-09-30T07:26:17Z

pycouchdb/client.py

+        :param params: Additional query parameters
+        :returns: Iterator yielding lists of documents for each page
+
+        .. versionadded: 1.17


The docstring format should be .. versionadded:: 1.17 with double colons, not single colon.

Suggested change

.. versionadded: 1.17

.. versionadded:: 1.17

…omment

Copilot

Pull Request Overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

Copilot · 2025-09-30T08:27:45Z

pycouchdb/pagination.py

+        last_row = rows[page_size - 1]
+        startkey = last_row['key']
+        startkey_docid = last_row['id']
+        skip = 1  # Skip the row used as the cursor to avoid returning it again (prevents duplicate results in cursor-based pagination)


[nitpick] The comment is overly verbose and could be clearer. Consider simplifying to 'Skip cursor row to avoid duplicates'.

Suggested change

skip = 1 # Skip the row used as the cursor to avoid returning it again (prevents duplicate results in cursor-based pagination)

skip = 1 # Skip cursor row to avoid duplicates

Copilot · 2025-09-30T08:27:45Z

pycouchdb/pagination.py

+        startkey = last_row['key']
+        startkey_docid = last_row['id']


The code uses magic string keys 'key' and 'id' without validation. Consider adding defensive checks or constants for these keys to improve maintainability.

Copilot · 2025-09-30T08:27:46Z

test/test_utils.py

+                # Valid JSON but with invalid UTF-8 sequence in the middle
+                self.content = b'{"key": "value", "invalid": "\xff\xfe"}'


The byte string contains invalid UTF-8 sequences inside a JSON string literal, but this creates invalid JSON, not just invalid UTF-8. The test may not be testing the intended scenario.

Suggested change

# Valid JSON but with invalid UTF-8 sequence in the middle

self.content = b'{"key": "value", "invalid": "\xff\xfe"}'

# Valid JSON, but the value for "invalid" is a string with bytes that are invalid UTF-8

self.content = b'{"key": "value", "invalid": "' + b'\xff\xfe'.decode("latin1").encode("utf-8", "surrogateescape") + b'"}'

Copilot · 2025-09-30T08:27:46Z

test/test_utils.py

+                # Valid JSON with invalid UTF-8 that will be replaced with replacement character
+                self.content = b'{"key": "value", "invalid": "\xff\xfe\x80"}'


Similar to the previous test, this creates invalid JSON syntax rather than testing UTF-8 decode errors. The invalid bytes should be outside the JSON string structure.

histrio added 4 commits September 30, 2025 09:22

feat(pagination): add cursor-based pagination + client APIs

15c8f54

docs(quickstart): document view and Mango pagination

77066dd

fix(utils): handle UnicodeDecodeError when parsing JSON

82e2787

test(pagination): add unit and integration coverage

27fa4f8

histrio requested a review from Copilot September 30, 2025 07:25

Copilot AI reviewed Sep 30, 2025

View reviewed changes

histrio added 4 commits September 30, 2025 09:31

fix(mypy): adjust Database.find return and add __all__ in pagination

b05fa86

docs(client): use correct Sphinx versionadded directive

a1cedde

refactor(pagination): remove unused mango helper and clarify cursor c…

e92077f

…omment

test(utils): cover as_json invalid UTF-8 with replacement chars

7aba7a6

histrio requested a review from Copilot September 30, 2025 08:25

Copilot AI reviewed Sep 30, 2025

View reviewed changes

docs(pagination): warn about unreliable pagination with reduced views

da5587e

histrio added the hacktoberfest-accepted label Oct 26, 2025

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	skip = 1 # Skip the row we used as cursor
	skip = 1 # Skip the row used as the cursor to avoid returning it again (prevents duplicate results in cursor-based pagination)

	skip = 1 # Skip the row used as the cursor to avoid returning it again (prevents duplicate results in cursor-based pagination)
	skip = 1 # Skip cursor row to avoid duplicates

		# Valid JSON but with invalid UTF-8 sequence in the middle
		self.content = b'{"key": "value", "invalid": "\xff\xfe"}'

		# Valid JSON with invalid UTF-8 that will be replaced with replacement character
		self.content = b'{"key": "value", "invalid": "\xff\xfe\x80"}'

feat(pagination): add cursor-based pagination + client APIs #112

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