Extract shared code patterns

Identify and extract repeated code patterns into reusable functions to improve maintainability and reduce duplication. When similar code appears in multiple places, create a shared helper function that captures the common logic.

Key guidelines:

• Extract code that differs only in a few parameters
• Create well-named helper functions that clearly describe their purpose
• Pass varying elements as parameters
• Consider creating dedicated types for related helpers

Example - Before:

func (tc *TransitiveClosures) Add(exprA, exprB sqlparser.Expr, comp string) {
    // Duplicate logic for handling expressions
    if tc.setA.contains(exprA) {
        // Complex logic A
    }
    if tc.setB.contains(exprB) {
        // Complex logic A repeated
    }
}

After:

func (tc *TransitiveClosures) handleExpr(expr sqlparser.Expr, set *exprSet) {
    // Shared logic extracted
    if set.contains(expr) {
        // Complex logic in one place
    }
}

func (tc *TransitiveClosures) Add(exprA, exprB sqlparser.Expr, comp string) {
    tc.handleExpr(exprA, tc.setA)
    tc.handleExpr(exprB, tc.setB)
}

This pattern reduces maintenance burden, improves readability, and makes the code easier to modify since changes only need to be made in one place.