Regexp operator in complex queries

Change-Id: I0db6c9f63c1de2e85b654beb2517eb215df9a323

specs/kilo/regexp-in-complex-query.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=======================
+Regexp in complex query
+=======================
+
+https://blueprints.launchpad.net/ceilometer/+spec/regexp-in-complex-query
+
+Problem description
+===================
+
+Currently some instance or network related service have extra identifier in
+resource_id. Example is disk.device.* metrics. They have resource_id
+with format - <instance_id>-<disk-id>. We can't make query for getting
+all samples from these meters with specified instance_id because disks have
+different ids. This behavior not easy for end users and adds troubles for
+someone who wants know more information about cluster work.
+
+Proposed change
+===============
+
+To support complex queries described above we should add new regex
+operator with corresponding "=~" designation.
+
+Implementation depends on backend:
+
+1) MongoDB and DB2. These dbs has $regex query support.
+It provides regular expression capabilities for pattern matching strings
+in queries. MongoDB and DB2 use Perl compatible regular expressions
+(i.e. “PCRE” ) version 8.30 with UTF-8 support. For correct work we map
+"=~" from filter query to "$regex" in pymongo request.
+
+2) SQLAlchemy. This backend supports "regexp" MySQL operator, also it's mapped
+
+3) HBase supports regexp queries with RegexStringComparator.
+
+Alternatives
+------------
+
+Add extra information to resource metadata
+
+Data model impact
+-----------------
+
+None.
+
+REST API impact
+---------------
+
+Add new simple operator "=~" in complex queries.
+
+Security impact
+---------------
+
+None.
+
+Pipeline impact
+---------------
+
+None
+
+Other end user impact
+---------------------
+
+You may make regex request in complex query.
+
+Performance/Scalability Impacts
+-------------------------------
+
+Will affect performance for large regular expressions,
+api service may be affected.
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  ityaptin
+
+Ongoing maintainer:
+  enovokshonova
+
+Work Items
+----------
+
+- add "=~" to simple operators list in controller
+- add regexp operator processing to backends
+
+Future lifecycle
+================
+
+None
+
+Dependencies
+============
+
+None.
+
+Testing
+=======
+
+- extend storage scenarios testing to include regexp operator
+
+Documentation Impact
+====================
+
+- update complex query notes to include new operator
+
+References
+==========
+
+https://blueprints.launchpad.net/ceilometer/+spec/regexp-in-complex-query