Function statementComplexity

pkg/advisor/optimizer.go:212–263

statementComplexity scores the complexity of a single statement.

(stmt ast.Statement)

// statementComplexity scores the complexity of a single statement.
func statementComplexity(stmt ast.Statement) int {
	score := 0

	switch s := stmt.(type) {
	case *ast.SelectStatement:
		// Base complexity
		score++

		// JOINs add complexity
		score += len(s.Joins)

		// Subqueries in FROM
		for _, from := range s.From {
			if from.Subquery != nil {
				score += 2
			}
		}

		// GROUP BY
		if len(s.GroupBy) > 0 {
			score++
		}

		// HAVING
		if s.Having != nil {
			score++
		}

		// Window functions
		if len(s.Windows) > 0 {
			score++
		}

		// CTE (WITH clause)
		if s.With != nil {
			score += len(s.With.CTEs)
		}

		// Subqueries in WHERE
		if s.Where != nil {
			score += countSubqueries(s.Where)
		}

	case *ast.SetOperation:
		score += statementComplexity(s.Left) + statementComplexity(s.Right) + 1

	default:
		score++
	}

	return score
}

// countSubqueries recursively counts subquery expressions in an expression tree.
func countSubqueries(expr ast.Expression) int {