Unfortunately, we encode the "target" of a secondary index in one of
three ways:
1. It can be just a column name
2. It can be a string like keys(colname) - for the new type of
collection indexes introduced in this series.
3. It can be a JSON map ({ ... }). This form is used for local indexes.
The code parsing this target - target_parser::parse() - needs not to
confuse these different formats. Before this patch, if the column name
contains special characters like braces or parentheses (this is allowed
in CQL syntax, via quoting), we can confuse case 1, 2, and 3: A column
named "keys(colname)" will be confused for case 2, and a column named
"{123}" will be confused with case 3.
This problem can break indexing of some specially-crafted column names -
as reproduced by test_secondary_index.py::test_index_quoted_names.
The solution adopted in this patch is that the column name in case 1
should be escaped somehow so it cannot be possibly confused with either
cases 2 and 3. The way we chose is to convert the column name to CQL (with
column_definition::as_cql_name()). In other words, if the column name
contains non-alphanumeric characters, it is wrapped in quotes and also
quotes are doubled, as in CQL. The result of this can't be confused
with case 2 or 3, neither of which may begin with a quote.
This escaping is not the minimal we could have done, but incidentally it
is exactly what Cassandra does as well, so I used it as well.
This change is *mostly* backward compatible: Already-existing indexes will
still have unescaped column names stored for their "target" string,
and the unescaping code will see they are not wrapped in quotes, and
not change them. Backward compatibility will only fail on existing indexes
on columns whose name begin and end in the quote characters - but this
case is extremely unlikely.
This patch illustrates how un-ideal our index "target" encoding is,
but isn't what made it un-ideal. We should not have used three different
formats for the index target - the third representation (JSON) should
have sufficed. However, two two other representations are identical
to Cassandra's, so using them when we can has its compatibility
advantages.
The patch makes test_secondary_index.py::test_index_quoted_names pass.
Fixes#10707.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
2c244c6e09