fix: detect misquoted tag values and return an error (#22754)

SHOW TAG KEYS FROM "foo" where bar="misquoted" is
erroneous, because the tag value must be enclosed
in single, not double, quotes. Although this
correctly returns no tag keys, it is very
inefficient and has cause out-of-memory failures
at a customer. This fix short-circuits the query.

closes #22755

(cherry picked from commit af9e89a)

tsdb/store.go

@@ -1537,6 +1537,9 @@ func (s *Store) TagKeys(ctx context.Context, auth query.FineAuthorizer, shardIDs
  }
  return e
  }), nil)
+ if err := isBadQuoteTagValueClause(filterExpr); err != nil {
+ return nil, err
+ }
 
  // Get all the shards we're interested in.
  is := IndexSet{Indexes: make([]Index, 0, len(shardIDs))}
@@ -1679,6 +1682,57 @@ func (a tagValuesSlice) Len() int { return len(a) }
 func (a tagValuesSlice) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
 func (a tagValuesSlice) Less(i, j int) bool { return bytes.Compare(a[i].name, a[j].name) == -1 }
 
+func isTagKeyClause(e influxql.Expr) (bool, error) {
+ switch e := e.(type) {
+ case *influxql.BinaryExpr:
+ switch e.Op {
+ case influxql.EQ, influxql.NEQ, influxql.EQREGEX, influxql.NEQREGEX:
+ tag, ok := e.LHS.(*influxql.VarRef)
+ if ok && tag.Val == "_tagKey" {
+ return true, nil
+ }
+ case influxql.OR, influxql.AND:
+ ok1, err := isTagKeyClause(e.LHS)
+ if err != nil {
+ return false, err
+ }
+ ok2, err := isTagKeyClause(e.RHS)
+ if err != nil {
+ return false, err
+ }
+ return ok1 && ok2, nil
+ }
+ case *influxql.ParenExpr:
+ return isTagKeyClause(e.Expr)
+ }
+ return false, nil
+}
+
+func isBadQuoteTagValueClause(e influxql.Expr) error {
+ switch e := e.(type) {
+ case *influxql.BinaryExpr:
+ switch e.Op {
+ case influxql.EQ, influxql.NEQ:
+ _, lOk := e.LHS.(*influxql.VarRef)
+ _, rOk := e.RHS.(*influxql.VarRef)
+ if lOk && rOk {
+ return fmt.Errorf("bad WHERE clause for metaquery; one term must be a string literal tag value within single quotes: %s", e.String())
+ }
+ case influxql.OR, influxql.AND:
+ if err := isBadQuoteTagValueClause(e.LHS); err != nil {
+ return err
+ } else if err = isBadQuoteTagValueClause(e.RHS); err != nil {
+ return err
+ } else {
+ return nil
+ }
+ }
+ case *influxql.ParenExpr:
+ return isBadQuoteTagValueClause(e.Expr)
+ }
+ return nil
+}
+
 // TagValues returns the tag keys and values for the provided shards, where the
 // tag values satisfy the provided condition.
 func (s *Store) TagValues(ctx context.Context, auth query.FineAuthorizer, shardIDs []uint64, cond influxql.Expr) ([]TagValues, error) {
@@ -1716,6 +1770,9 @@ func (s *Store) TagValues(ctx context.Context, auth query.FineAuthorizer, shardI
  return e
  }), nil)
 
+ if err := isBadQuoteTagValueClause(filterExpr); err != nil {
+ return nil, err
+ }
  // Build index set to work on.
  is := IndexSet{Indexes: make([]Index, 0, len(shardIDs))}
  s.mu.RLock()