func checkEquivExpr(a, b parser.Expr, qvals qvalMap) error {
// The expressions above only use the values 1 and 2. Verify that the
// simplified expressions evaluate to the same value as the original
// expression for interesting values.
zero := parser.DInt(0)
for _, v := range []parser.Datum{zero, zero + 1, zero + 2, zero + 3, parser.DNull} {
for _, q := range qvals {
q.datum = v
}
da, err := a.Eval(parser.EvalContext{})
if err != nil {
return fmt.Errorf("%s: %v", a, err)
}
db, err := b.Eval(parser.EvalContext{})
if err != nil {
return fmt.Errorf("%s: %v", b, err)
}
// This is tricky: we don't require the expressions to produce identical
// results, but to either both return true or both return not true (either
// false or NULL).
if (da == parser.DBool(true)) != (db == parser.DBool(true)) {
return fmt.Errorf("%s: %s: expected %s, but found %s", a, v, da, db)
}
}
return nil
}
// runFilter runs a filter expression and returs whether the filter passes.
func runFilter(filter parser.Expr, evalCtx parser.EvalContext) (bool, error) {
if filter == nil {
return true, nil
}
d, err := filter.Eval(evalCtx)
if err != nil {
return false, err
}
return d != parser.DNull && bool(d.(parser.DBool)), nil
}