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sql: introduce persistedsqlstats subsystem
This commit introduces a new persisted sql stats subsystem that wraps the existing node-local sql stats subsystem. This new subsystem is responsible for flushing the in-meory statistics into the system table periodically, or when it detects memory pressure. This replaces sql.Server's in-memory sqlStats provider. Release note (sql change): SQL stats now can be persisted into system.statement_statistics and system.transaction_statistics tables by enabling the sql.stats.flush.enable cluster setting. The interval of persistence is determined by the new sql.stats.flush.interval cluster setting which defaults to 1 hour.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,90 @@ | ||
| // Copyright 2021 The Cockroach Authors. | ||
| // | ||
| // Use of this software is governed by the Business Source License | ||
| // included in the file licenses/BSL.txt. | ||
| // | ||
| // As of the Change Date specified in that file, in accordance with | ||
| // the Business Source License, use of this software will be governed | ||
| // by the Apache License, Version 2.0, included in the file | ||
| // licenses/APL.txt. | ||
|
|
||
| package persistedsqlstats | ||
|
|
||
| import ( | ||
| "context" | ||
|
|
||
| "github.com/cockroachdb/cockroach/pkg/roachpb" | ||
| "github.com/cockroachdb/cockroach/pkg/sql/execstats" | ||
| "github.com/cockroachdb/cockroach/pkg/sql/sqlstats" | ||
| "github.com/cockroachdb/cockroach/pkg/sql/sqlstats/ssmemstorage" | ||
| "github.com/cockroachdb/errors" | ||
| ) | ||
|
|
||
| // StatsWriter is a sqlstats.Writer that wraps a in-memory node-local stats | ||
| // writer. StatsWriter signals the subsystem when it encounters memory pressure | ||
| // which will triggers the flush operation. | ||
| type StatsWriter struct { | ||
| // local in-memory storage. | ||
| memWriter sqlstats.Writer | ||
|
|
||
| // Use to signal the stats writer is experiencing memory pressure. | ||
| memoryPressureSignal chan struct{} | ||
| } | ||
|
|
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| var _ sqlstats.Writer = &StatsWriter{} | ||
|
|
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| // RecordStatement implements sqlstats.Writer interface. | ||
| func (s *StatsWriter) RecordStatement( | ||
| ctx context.Context, key roachpb.StatementStatisticsKey, value sqlstats.RecordedStmtStats, | ||
| ) (roachpb.StmtFingerprintID, error) { | ||
| var fingerprintID roachpb.StmtFingerprintID | ||
| err := s.recordStatsOrSendMemoryPressureSignal(func() (err error) { | ||
| fingerprintID, err = s.memWriter.RecordStatement(ctx, key, value) | ||
| return err | ||
| }) | ||
| return fingerprintID, err | ||
| } | ||
|
|
||
| // RecordStatementExecStats implements sqlstats.Writer interface. | ||
| func (s *StatsWriter) RecordStatementExecStats( | ||
| key roachpb.StatementStatisticsKey, stats execstats.QueryLevelStats, | ||
| ) error { | ||
| return s.memWriter.RecordStatementExecStats(key, stats) | ||
| } | ||
|
|
||
| // ShouldSaveLogicalPlanDesc implements sqlstats.Writer interface. | ||
| func (s *StatsWriter) ShouldSaveLogicalPlanDesc( | ||
| fingerprint string, implicitTxn bool, database string, | ||
| ) bool { | ||
| return s.memWriter.ShouldSaveLogicalPlanDesc(fingerprint, implicitTxn, database) | ||
| } | ||
|
|
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| // RecordTransaction implements sqlstats.Writer interface and saves | ||
| // per-transaction statistics. | ||
| func (s *StatsWriter) RecordTransaction( | ||
| ctx context.Context, key roachpb.TransactionFingerprintID, value sqlstats.RecordedTxnStats, | ||
| ) error { | ||
| return s.recordStatsOrSendMemoryPressureSignal(func() error { | ||
| return s.memWriter.RecordTransaction(ctx, key, value) | ||
| }) | ||
| } | ||
|
|
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| func (s *StatsWriter) recordStatsOrSendMemoryPressureSignal(fn func() error) error { | ||
| err := fn() | ||
| if errors.Is(err, ssmemstorage.ErrFingerprintLimitReached) || errors.Is(err, ssmemstorage.ErrMemoryPressure) { | ||
| select { | ||
| case s.memoryPressureSignal <- struct{}{}: | ||
| // If we successfully signaled that we are experiencing memory pressure, | ||
| // then our job is done. However, if we fail to send the signal, that | ||
| // means we are already experiencing memory pressure and the | ||
| // stats-flush-worker has already started to handle the flushing. We | ||
| // don't need to do anything here at this point. The default case of the | ||
| // select allows this operation to be non-blocking. | ||
| default: | ||
| } | ||
| // We have already handled the memory pressure error. We don't have to | ||
| // bubble up the error any further. | ||
| return nil | ||
| } | ||
| return err | ||
| } |