Function mergeFilters

compiler/optimizer/optimizer.go:42–58

mergeFilters transforms the DAG by merging adjacent filter operators so that, e.g., "where a | where b" becomes "where a and b". Note: mergeFilters does not descend into dag.OverExpr.Scope, so it cannot merge filters in "over" expressions like "sum(over a | where b | where c)".

(seq dag.Seq)

// Note: mergeFilters does not descend into dag.OverExpr.Scope, so it cannot
// merge filters in "over" expressions like "sum(over a | where b | where c)".
func mergeFilters(seq dag.Seq) dag.Seq {
	walkT(reflect.ValueOf(&seq), func(seq dag.Seq) dag.Seq {
		// Start at the next to last element and work toward the first.
		for i := len(seq) - 2; i >= 0; i-- {
			if f1, ok := seq[i].(*dag.FilterOp); ok {
				if f2, ok := seq[i+1].(*dag.FilterOp); ok {
					// Merge the second filter into the
					// first and then delete the second.
					f1.Expr = dag.NewBinaryExpr("and", f1.Expr, f2.Expr)
					seq.Delete(i+1, i+2)
				}
			}
		}
		return seq
	})
	return seq
}

func removePassOps(seq dag.Seq) dag.Seq {
	return Walk(seq, func(seq dag.Seq) dag.Seq {