fix: skip autovacuum metric when xact_start is NULL - #1381
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The stat_activity_autovacuum collector scanned xact_start into a plain float64, so a NULL value (possible for autovacuum workers) failed the whole collector with "converting NULL to float64 is unsupported". Scan into sql.NullFloat64 and skip the row when it is NULL, matching the pg_stat_walreceiver / pg_stat_database collectors. Fixes prometheus-community#952 Signed-off-by: Dean Chen <862469039@qq.com>
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The stat_activity_autovacuum collector scans
EXTRACT(EPOCH FROM xact_start)into a plainfloat64.xact_startcan be NULL for autovacuum workers, and when that happens the Scan fails withconverting NULL to float64 is unsupportedand the entire collector errors out, as reported in #952.This changes the scan target to
sql.NullFloat64and skips the row when the value is NULL, following the same pattern the pg_stat_walreceiver and pg_stat_database collectors use. Skipping rather than reporting 0 matches sysadmind's comment on the issue: "The typical options are to report a 0 value or to skip the metric all together. I usually lean towards the latter." Rows with a valid timestamp keep being emitted as before.The regression test adds a NULL-timestamp row mixed with a normal row; it reproduces the exact Scan error before the fix and verifies the NULL row is skipped and the valid row still emitted after.
Fixes #952