Issues with sql_mode=only_full_group_by in perf_schema_events_statements

[galexrt]

I'm getting errors in the logs:

time="2017-05-20T17:07:50Z" level=error msg="Error scraping for collect.perf_schema.eventsstatements: Error 1055: Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'Q.DIGEST_TEXT' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by" source="mysqld_exporter.go:359"

The query that's causing this seems to be:

mysqld_exporter/collector/perf_schema_events_statements.go

Lines 13 to 40 in 82e9cb5

	const perfEventsStatementsQuery = `
	SELECT
	ifnull(SCHEMA_NAME, 'NONE') as SCHEMA_NAME,
	DIGEST,
	LEFT(DIGEST_TEXT, %d) as DIGEST_TEXT,
	COUNT_STAR,
	SUM_TIMER_WAIT,
	SUM_ERRORS,
	SUM_WARNINGS,
	SUM_ROWS_AFFECTED,
	SUM_ROWS_SENT,
	SUM_ROWS_EXAMINED,
	SUM_CREATED_TMP_DISK_TABLES,
	SUM_CREATED_TMP_TABLES,
	SUM_SORT_MERGE_PASSES,
	SUM_SORT_ROWS,
	SUM_NO_INDEX_USED
	FROM (
	SELECT *
	FROM performance_schema.events_statements_summary_by_digest
	WHERE SCHEMA_NAME NOT IN ('mysql', 'performance_schema', 'information_schema')
	AND LAST_SEEN > DATE_SUB(NOW(), INTERVAL %d SECOND)
	ORDER BY LAST_SEEN DESC
	)Q
	GROUP BY SCHEMA_NAME, DIGEST
	ORDER BY SUM_TIMER_WAIT DESC
	LIMIT %d
	`

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If you need any more info about this issue, please let me know.

[SuperQ]

ONLY_FULL_GROUP_BY seems to be a new feature of MySQL >= 5.7.5.

We will need to fix this query in order to make this collector work with newer versions.