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release-20.2: sql: emit more tracing events from the stats cache #54190

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merged 2 commits into from
Sep 16, 2020
Merged

release-20.2: sql: emit more tracing events from the stats cache #54190

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8ce789a
sql: emit more tracing events from the stats cache
RaduBerinde Sep 9, 2020
b79c514
opt: add more tracing events around planning
RaduBerinde Sep 9, 2020
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3 changes: 3 additions & 0 deletions pkg/sql/plan_opt.go
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Original file line number Diff line number Diff line change
Expand Up @@ -405,6 +405,7 @@ func (opc *optPlanningCtx) buildReusableMemo(ctx context.Context) (_ *memo.Memo,
// operators that can be constant folded, then fully optimize it now - it
// can be reused without further changes to build the execution tree.
if !f.Memo().HasPlaceholders() && !f.FoldingControl().PreventedStableFold() {
opc.log(ctx, "optimizing (no placeholders)")
if _, err := opc.optimizer.Optimize(); err != nil {
return nil, err
}
Expand Down Expand Up @@ -499,6 +500,8 @@ func (opc *optPlanningCtx) buildExecMemo(ctx context.Context) (_ *memo.Memo, _ e
}
opc.flags.Set(planFlagOptCacheMiss)
opc.log(ctx, "query cache miss")
} else {
opc.log(ctx, "not using query cache")
}

// We are executing a statement for which there is no reusable memo
Expand Down
33 changes: 15 additions & 18 deletions pkg/sql/stats/stats_cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ import (
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/protoutil"
"github.com/cockroachdb/cockroach/pkg/util/syncutil"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"github.com/cockroachdb/errors"
)

Expand Down Expand Up @@ -188,11 +189,11 @@ func (sc *TableStatisticsCache) lookupStatsLocked(
if e.mustWait {
// We are in the process of grabbing stats for this table. Wait until
// that is complete, at which point e.stats will be populated.
if log.V(1) {
log.Infof(ctx, "waiting for statistics for table %d", tableID)
}
log.VEventf(ctx, 1, "waiting for statistics for table %d", tableID)
e.waitCond.Wait()
log.VEventf(ctx, 1, "finished waiting for statistics for table %d", tableID)
} else {
// This is the expected "fast" path; don't emit an event.
if log.V(2) {
log.Infof(ctx, "statistics for table %d found in cache", tableID)
}
Expand All @@ -211,10 +212,6 @@ func (sc *TableStatisticsCache) lookupStatsLocked(
func (sc *TableStatisticsCache) addCacheEntryLocked(
ctx context.Context, tableID descpb.ID,
) (stats []*TableStatistic, err error) {
if log.V(1) {
log.Infof(ctx, "reading statistics for table %d", tableID)
}

// Add a cache entry that other queries can find and wait on until we have the
// stats.
e := &cacheEntry{
Expand All @@ -228,7 +225,9 @@ func (sc *TableStatisticsCache) addCacheEntryLocked(
sc.mu.Unlock()
defer sc.mu.Lock()

log.VEventf(ctx, 1, "reading statistics for table %d", tableID)
stats, err = sc.getTableStatsFromDB(ctx, tableID)
log.VEventf(ctx, 1, "finished reading statistics for table %d", tableID)
}()

e.mustWait = false
Expand Down Expand Up @@ -258,10 +257,6 @@ func (sc *TableStatisticsCache) refreshCacheEntry(ctx context.Context, tableID d
sc.mu.Lock()
defer sc.mu.Unlock()

if log.V(1) {
log.Infof(ctx, "reading statistics for table %d", tableID)
}

// If the stats don't already exist in the cache, don't bother performing
// the refresh. If e.err is not nil, the stats are in the process of being
// removed from the cache (see addCacheEntryLocked), so don't refresh in this
Expand All @@ -287,7 +282,9 @@ func (sc *TableStatisticsCache) refreshCacheEntry(ctx context.Context, tableID d
sc.mu.Unlock()
defer sc.mu.Lock()

log.VEventf(ctx, 1, "refreshing statistics for table %d", tableID)
stats, err = sc.getTableStatsFromDB(ctx, tableID)
log.VEventf(ctx, 1, "done refreshing statistics for table %d", tableID)
}()
if !e.mustRefreshAgain {
break
Expand All @@ -307,11 +304,13 @@ func (sc *TableStatisticsCache) refreshCacheEntry(ctx context.Context, tableID d
// RefreshTableStats refreshes the cached statistics for the given table ID
// by fetching the new stats from the database.
func (sc *TableStatisticsCache) RefreshTableStats(ctx context.Context, tableID descpb.ID) {
if log.V(1) {
log.Infof(ctx, "refreshing statistics for table %d", tableID)
}
log.VEventf(ctx, 1, "refreshing statistics for table %d", tableID)
ctx, span := tracing.ForkCtxSpan(ctx, "refresh-table-stats")
// Perform an asynchronous refresh of the cache.
go sc.refreshCacheEntry(ctx, tableID)
go func() {
defer tracing.FinishSpan(span)
sc.refreshCacheEntry(ctx, tableID)
}()
}

// InvalidateTableStats invalidates the cached statistics for the given table ID.
Expand All @@ -320,9 +319,7 @@ func (sc *TableStatisticsCache) RefreshTableStats(ctx context.Context, tableID d
// This function is used only when we want to guarantee that the next query
// uses updated stats.
func (sc *TableStatisticsCache) InvalidateTableStats(ctx context.Context, tableID descpb.ID) {
if log.V(1) {
log.Infof(ctx, "evicting statistics for table %d", tableID)
}
log.VEventf(ctx, 1, "evicting statistics for table %d", tableID)
sc.mu.Lock()
defer sc.mu.Unlock()
sc.mu.cache.Del(tableID)
Expand Down