code: func (c *index) Seek(sc *stmtctx.StatementContext, r kv.Retriever, indexedValues []types.Datum) (iter table.IndexIterator, hit bool, err error) {
  	key, _, err := c.GenIndexKey(sc, indexedValues, 0, nil)
  	if err != nil {
  		return nil, false, err
  	}
  
  	upperBound := c.prefix.PrefixNext()
  	it, err := r.Iter(key, upperBound)
  	if err != nil {
  		return nil, false, err
  	}
  	// check if hit
  	hit = false
  	if it.Valid() && it.Key().Cmp(key) == 0 {
  		hit = true
  	}
  	return &indexIter{it: it, idx: c, prefix: c.prefix}, hit, nil
  }
docs: // Seek searches KV index for the entry with indexedValues.