/* Constrain the WHERE condition to reflect the aggregate query. For example: SELECT AVG(v) FROM widget w; is rewritten as: SELECT AVG(v) FROM widget w WHERE v IS NOT NULL; This enables the query to use an index on v. */ func constrainAggregate(cond expression.Expression, aggs map[string]algebra.Aggregate) expression.Expression { var first expression.Expression for _, agg := range aggs { if first == nil { first = agg.Operand() if first == nil { return cond } continue } op := agg.Operand() if op == nil || !first.EquivalentTo(op) { return cond } } if first == nil { return cond } var constraint expression.Expression = expression.NewIsNotNull(first) if cond != nil { constraint = expression.NewAnd(cond, constraint) } return constraint }
func newSubsetDefault(expr expression.Expression) *subsetDefault { rv := &subsetDefault{} rv.test = func(expr2 expression.Expression) (bool, error) { value2 := expr2.Value() if value2 != nil { return value2.Truth(), nil } if expr.EquivalentTo(expr2) { return true, nil } switch expr2 := expr2.(type) { case *expression.And: for _, op := range expr2.Operands() { if !SubsetOf(expr, op) { return false, nil } } return true, nil case *expression.Or: for _, op := range expr2.Operands() { if SubsetOf(expr, op) { return true, nil } } return false, nil case *expression.IsNotMissing: return expr.PropagatesMissing() && expr.DependsOn(expr2.Operand()), nil case *expression.IsNotNull: return expr.PropagatesNull() && expr.DependsOn(expr2.Operand()), nil case *expression.IsValued: return expr.PropagatesNull() && expr.DependsOn(expr2.Operand()), nil } return false, nil } return rv }
func LessThanOrEquals(expr1, expr2 expression.Expression) bool { return LessThan(expr1, expr2) || expr1.EquivalentTo(expr2) }