Fix mysql.index.reads/updates/deletes submitted as gauge instead of monotonic_count

[pierreln-dd]

What does this PR do?

QUERY_INDEX_USAGE in index_metrics.py collects count_read, count_update, and count_delete from performance_schema.table_io_waits_summary_by_index_usage. These are cumulative counters, but they were submitted with 'type': 'gauge', causing mysql.index.reads, mysql.index.updates, and mysql.index.deletes to report raw monotonically increasing totals rather than per-interval counts.

This PR changes the metric type to monotonic_count, consistent with how other cumulative performance_schema counters are handled in this check (e.g. mysql.innodb.deadlocks, mysql.performance.wait_event.count).

Motivation

Customer escalation (SDBM-2685): after upgrading from MariaDB 10.6 to 11.4, mysql.index.reads/updates/deletes appeared as continuously increasing values in dashboards. Root cause confirmed in code and reproduced in staging (datad0g.com): all MySQL/MariaDB/Aurora hosts with performance_schema enabled show the same monotonically increasing pattern.

The bug affects all agents ≥ 7.63.0 (when index_metrics shipped in integration 14.5.0). It is not MariaDB-specific — confirmed present on Aurora MySQL in staging as well.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add qa/required if this PR needs QA validation, or qa/skip-qa if it does not. Exactly one of the two is required.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[datadog-prod-us1-5]

 

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 90.30% (+2.40%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: c573510 | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Validation Report

All 21 validations passed.

Show details

Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and code coverage settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
qa-label	Validate the pull request declares whether it needs QA for the next Agent release	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

View full run