Andrés de la Peña created CASSANDRA-7575:
--------------------------------------------
Summary: Custom 2i validation
Key: CASSANDRA-7575
URL: https://issues.apache.org/jira/browse/CASSANDRA-7575
Project: Cassandra
Issue Type: Improvement
Components: API
Reporter: Andrés de la Peña
Priority: Minor
Attachments: 2i_validation.patch
There are several projects using custom secondary indexes as an extension point
to integrate C* with other systems such as Solr or Lucene. The usual approach
is to embed third party indexing queries in CQL clauses.
For example, [DSE
Search|http://www.datastax.com/what-we-offer/products-services/datastax-enterprise]
embeds Solr syntax this way:
{code}
SELECT title FROM solr WHERE solr_query='title:natio*';
{code}
[Stratio platform|https://github.com/Stratio/stratio-cassandra] embeds custom
JSON syntax for searching in Lucene indexes:
{code}
SELECT * FROM tweets WHERE lucene='{
filter : {
type: "range",
field: "time",
lower: "2014/04/25",
upper: "2014/04/1"
},
query : {
type: "phrase",
field: "body",
values: ["big", "data"]
},
sort : {fields: [ {field:"time", reverse:true} ] }
}';
{code}
Tuplejump [Stargate|http://tuplejump.github.io/stargate/] also uses the
Stratio's open source JSON syntax:
{code}
SELECT name,company FROM PERSON WHERE stargate ='{
filter: {
type: "range",
field: "company",
lower: "a",
upper: "p"
},
sort:{
fields: [{field:"name",reverse:true}]
}
}';
{code}
These syntaxes are validated by the corresponding 2i implementation. This
validation is done behind the StorageProxy command distribution. So, far as I
know, there is no way to give rich feedback about syntax errors to CQL users.
I'm uploading a patch with some changes trying to improve this. I propose
adding an empty validation method to SecondaryIndexSearcher that can be
overridden by custom 2i implementations:
{code}
public void validate(List<IndexExpression> clause) {}
{code}
And call it from SelectStatement#getRangeCommand:
{code}
ColumnFamilyStore cfs =
Keyspace.open(keyspace()).getColumnFamilyStore(columnFamily());
for (SecondaryIndexSearcher searcher :
cfs.indexManager.getIndexSearchersForQuery(expressions))
{
try
{
searcher.validate(expressions);
}
catch (RuntimeException e)
{
String exceptionMessage = e.getMessage();
if (exceptionMessage != null
&& !exceptionMessage.trim().isEmpty())
throw new InvalidRequestException(
"Invalid index expression: " + e.getMessage());
else
throw new InvalidRequestException(
"Invalid index expression");
}
}
{code}
In this way C* allows custom 2i implementations to give feedback about syntax
errors.
We are currently using these changes in a fork with no problems.
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