Remove deprecated signatures of pgr maxCardinalityMatch

[cvvergara]

Fixes #2899

Changes proposed in this pull request:

• Remove SQL deprecated signatures and functions
• pgtap tests to be done only on existing SQL functions
• Keeping deprecated internal C function
  • Moving to legacy will happen on v5

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[cvvergara]

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🏁 Script executed:

#!/bin/bash
# Get basic information about the PR
gh pr view 2900 --json title,body,author,baseRefName,headRefName,files,additions,deletions

# Get the list of changed files with their status
gh pr diff 2900 --name-status

# Get the actual diff to understand the changes
gh pr diff 2900

Length of output: 43250

---

@cvvergara Here's the summary and review for PR #2900:

Summary

This PR removes deprecated signatures of pgr_maxCardinalityMatch function as part of the v4.0.0 cleanup. The changes include:

Key Changes:

• API Simplification: Removes the deprecated pgr_maxCardinalityMatch(text, boolean) signature, keeping only pgr_maxCardinalityMatch(text)
• New Infrastructure: Introduces UndirectedNoCostsBG class for handling undirected graphs without costs
• Return Type Change: Function now returns SETOF BIGINT (edge IDs only) instead of the previous record structure with sequence, edge, source, and target
• Code Refactoring: Moves from inline graph construction to a dedicated graph class with proper separation of concerns

Files Modified:

• 24 files with 385 additions and 323 deletions
• New files: undirectedNoCostBG.hpp/cpp, updated maximumcardinalitymatching.cpp
• Updated SQL definitions, tests, documentation, and release notes

Review

✅ Strengths

1. Clean API Design: Removing the directed parameter simplifies the API since maximum cardinality matching is inherently for undirected graphs.

2. Better Code Organization: The new UndirectedNoCostsBG class provides a clean abstraction for undirected graphs:

class UndirectedNoCostsBG {
    using G = boost::adjacency_list<boost::listS, boost::vecS, boost::undirectedS>;
    // Clean interface with proper encapsulation
};

3. Improved Function Interface: The new internal function _pgr_maxCardinalityMatch_v4 has a cleaner signature:

void pgr_do_maximum_cardinality_matching(
    const char *edges_sql,
    int64_t **return_tuples,  // Simplified return type
    size_t *return_count,
    // ... error handling
);

4. Comprehensive Test Updates: All test files have been properly updated to reflect the API changes.

🔍 Areas for Attention

1. Memory Management: In undirectedNoCostBG.cpp, ensure proper cleanup:

if (edge.going) {
    boost::tie(e, added) = boost::add_edge(v1, v2, graph);
    if (added) E_to_id.insert(std::pair<E, int64_t>(e, edge.id));
}

The conditional insertion looks correct, but verify edge deduplication behavior.

2. Error Handling: In maximumcardinalitymatching.cpp:

boost::tie(e, exists) = boost::edge(v1, v2, graph());
if (!exists) throw;  // Consider more descriptive error

The bare throw should probably throw a more specific exception.

3. Legacy Function: The deprecated _pgr_maxcardinalitymatch function is kept but returns dummy values:

values[0] = 0;  // seq
values[1] = Int64GetDatum(result_tuples[funcctx->call_cntr]);  // edge
values[2] = 0;  // source  
values[3] = 0;  // target

Consider adding a deprecation warning when this function is called.

📋 Recommendations

1. Exception Handling: Replace bare throw with descriptive exceptions:

if (!exists) {
    throw std::runtime_error("Edge does not exist in matching result");
}

2. Documentation: Consider adding inline documentation for the new UndirectedNoCostsBG class methods.

3. Validation: Add validation in the constructor to ensure edges reference valid vertices.

✅ Overall Assessment

This is a well-executed refactoring that successfully:

• Removes deprecated functionality as planned for v4.0.0
• Introduces cleaner abstractions
• Maintains backward compatibility where needed
• Updates all related components consistently

The code quality is good and the approach is sound. The changes align well with the goal of cleaning up the API for the major version release.