func checkEquivExpr(a, b parser.TypedExpr, sel *selectNode) 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.
for _, v := range []parser.Datum{
parser.NewDInt(0),
parser.NewDInt(1),
parser.NewDInt(2),
parser.NewDInt(3),
parser.DNull,
} {
for i := range sel.curSourceRow {
sel.curSourceRow[i] = v
}
ctx := &parser.EvalContext{}
da, err := a.Eval(ctx)
if err != nil {
return fmt.Errorf("%s: %v", a, err)
}
db, err := b.Eval(ctx)
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.DBoolTrue) != (db == parser.DBoolTrue) {
return fmt.Errorf("%s: %s: expected %s, but found %s", a, v, da, db)
}
}
return nil
}
// RunFilter runs a filter expression and returns whether the filter passes.
func RunFilter(filter parser.TypedExpr, 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
}