Extended the InfluxQL rewriter to handle SELECT statements with nested
sub-queries, as well as EXPLAIN statements.
Tests were added to check all the rewrite cases for happy path and
failure modes.
feat: add query_influxql api
This PR adds support for the /api/v3/query_influxql API. This re-uses code from the existing query_sql API, but some refactoring was done to allow for code re-use between the two.
The main change to the original code from the existing query_sql API was that the format is determined up front, in the event that the user provides some incorrect Accept header, so that the 400 BAD REQUEST is returned before performing the query.
Support of several InfluxQL queries that previously required a bridge to be executed in 3.0 was added:
SHOW MEASUREMENTS
SHOW TAG KEYS
SHOW TAG VALUES
SHOW FIELD KEYS
SHOW DATABASES
Handling of qualified measurement names in SELECT queries (see below)
This is accomplished with the newly added iox_query_influxql_rewrite crate, which provides the means to re-write an InfluxQL statement to strip out a database name and retention policy, if provided. Doing so allows the query_influxql API to have the database parameter optional, as it may be provided in the query string.
Handling qualified measurement names in SELECT
The implementation in this PR will inspect all measurements provided in a FROM clause and extract the database (DB) name and retention policy (RP) name (if not the default). If multiple DB/RP's are provided, an error is thrown.
Testing
E2E tests were added for performing basic queries against a running server on both the query_sql and query_influxql APIs. In addition, the test for query_influxql includes some of the InfluxQL-specific queries, e.g., SHOW MEASUREMENTS.
Other Changes
The influxdb3_client now has the api_v3_query_influxql method (and a basic test was added for this)
Trevor Hilton