Add option to select SQL engine with each query.

[Yury-Fridlyand]

Signed-off-by: Yury-Fridlyand [email protected]

Description

This adds a new URL parameter engine, which controls SQL engine selection.
Acceptable values (case insensitive):

• v1 or legacy
• v2

If it is not given or has another value, the default strategy is used - V2 with fallback to V1.
Could be used for _explain request as well.
These changes include also support of this parameter by SQL CLI and JDBC driver too.

Examples

Rest API

Add new parameter to URL (in any order):

...?engine=v2
...?format=jdbc&engine=legacy

Examples:

Query not supported by V2 sent to V2:

curl -XPOST "http://localhost:9200/_plugins/_sql?engine=v2" -H 'Content-Type: application/json' -d '{"query": "select COUNT(*) from calcs, calcs"}'

Query not supported by V1 sent to V1:

curl -XPOST "http://localhost:9200/_plugins/_sql?engine=v1" -H 'Content-Type: application/json' -d '{"query": "select 1"}'

SQL CLI tool:

New command line option:

opensearchsql --engine v1

JDBC driver

Add new parameter to connection string (in any order)

...?engine=v2
...?auth=BASIC&engine=v1

Notes

1. Please, consider that it is not a production feature and it should be removed soon. I made it as simple as possible.
2. It is supposed to be removed/reverted before next release. If needed it could be restored back after release.

Issues Resolved

N/A

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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