Avoid adding sql mem metrics twice

[jsoriano]

SQL memory metrics are registered twice and they are also reported
twice by metrics exporters. This is specially strange on Prometheus
histograms, where buckets are duplicated:

sql_mem_sql_txn_max_bucket{le="+Inf"} 0.0
sql_mem_sql_txn_max_sum 0.0
sql_mem_sql_txn_max_count 0.0
sql_mem_sql_txn_max_bucket{le="+Inf"} 0.0
sql_mem_sql_txn_max_sum 0.0
sql_mem_sql_txn_max_count 0.0

Release note (bug fix): Remove duplicated SQL memory metrics.

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[cockroach-teamcity]

This change is 

[jsoriano]

Here:

cockroach/pkg/server/server_sql.go

Lines 505 to 507 in 081a3a7

	for _, m := range pgServer.Metrics() {
	cfg.registry.AddMetricStruct(m)
	}

[jsoriano]

Hey @RaduBerinde, I have seen you have been working on some SQL telemetry fixes recently. Maybe you can review this PR? 🙂 Thanks!

[RaduBerinde]

Thanks!

Reviewable status: complete! 1 of 0 LGTMs obtained

[jsoriano]

@RaduBerinde thanks for the review, do you know if there is anything else needed to have this merged? 🙂

[RaduBerinde]

Oh, sorry, merging now.

bors r+

[craig]

Build succeeded

• GitHub CI (Cockroach)

[SWDevAngel]

@jsoriano Hi Jaime. Thank you for contributing to CockroachDB this year. As a token of our appreciation we would like to send you a gift. Please DM me on our community Slack @lisa so I can send you a link. (If you don’t want a gift, we also have a charitable contribution choice.) All orders need to be in by December 13, so please send this asap. :)