SQLAlchemy instrumentor populates span after sqlcomment creation, not before

[tammy-baylis-swi]

Description

Re-orders database query span population by SQLAlchemy instrumentor so that db.statement span attribute includes any sqlcomments generated.

Fixes #2938

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Added unit test. Locally installed this version of opentelemetry-instrumentation-sqlalchemy and upstream dependencies. Instrumented a Flask app that queries MySQL (via mysql-connector driver) with general logs enabled to check sqlcomment (enabled as per doc). Spans were exported to a locally-running otel-collector to inspect attributes including db.statement.

After changes, example span from SQLAlchemy-with-mysql-connector query with updated db.statement:

InstrumentationScope opentelemetry.instrumentation.sqlalchemy 0.49b0.dev
Span #0
    Trace ID       : 3b654158a48190e458f6c4e15e125814
    Parent ID      : ed65cfad7167aecd
    ID             : 69d58000ef348179
    Name           : connect
    Kind           : Client
    Start time     : 2024-10-29 22:09:35.42945621 +0000 UTC
    End time       : 2024-10-29 22:09:35.466973419 +0000 UTC
    Status code    : Unset
    Status message :
Attributes:
     -> net.peer.name: Str(mysql-world-db)
     -> net.peer.port: Int(3306)
     -> db.name: Str(world)
     -> db.user: Str(world)
     -> db.system: Str(mysql)
Span #1
    Trace ID       : 3b654158a48190e458f6c4e15e125814
    Parent ID      : ed65cfad7167aecd
    ID             : b62c6e3e794e9f05
    Name           : SELECT world
    Kind           : Client
    Start time     : 2024-10-29 22:09:35.469197169 +0000 UTC
    End time       : 2024-10-29 22:09:35.469996085 +0000 UTC
    Status code    : Unset
    Status message :
Attributes:
     -> db.statement: Str(SELECT city.id, city.name, city.district, city.population, city.countrycode
FROM city
WHERE city.id = %(id_1)s /*db_driver='mysqlconnector',db_framework='sqlalchemy%%3A2.0.36',traceparent='00-3b654158a48190e458f6c4e15e125814-b62c6e3e794e9f05-01'*/)
     -> db.system: Str(mysql)
     -> net.peer.name: Str(mysql-world-db)
     -> net.peer.port: Int(3306)
     -> db.name: Str(world)
     -> db.user: Str(world)

which matches sqlcomment in corresponding MySQL general log:

2024-10-29T22:09:35.469520Z	  240 Query	SELECT city.id, city.name, city.district, city.population, city.countrycode
FROM city
WHERE city.id = '1818' /*db_driver='mysqlconnector',db_framework='sqlalchemy%%3A2.0.36',traceparent='00-3b654158a48190e458f6c4e15e125814-b62c6e3e794e9f05-01'*/

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[tammy-baylis-swi]

Working on fixing these new failures -- done in 7b78383