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fix: change metrics PK for better memory usage #2545

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Merged
kodiakhq merged 7 commits into from
Jul 2, 2026
+63 −37
Merged

fix: change metrics PK for better memory usage #2545

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093544b
fix: change metrics PK for better memory usage
knudtty Jun 29, 2026
b55c111
fix: change Delta encoding to underlying datatype byte number
knudtty Jun 30, 2026
ff6690f
fix: all MetricName should be LowCardinality
knudtty Jun 30, 2026
39060a7
Merge remote-tracking branch 'origin/main' into aaron/metrics-reduce-…
knudtty Jul 1, 2026
060c03c
fix: edge case for interval range for toStartOf functions in chart
knudtty Jul 1, 2026
a394f9c
add changeset
knudtty Jul 2, 2026
4e5a5f1
Merge branch 'main' into aaron/metrics-reduce-pk-memory
knudtty Jul 2, 2026
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55 changes: 30 additions & 25 deletions docker/otel-collector/schema/seed/00003_otel_metrics.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -9,16 +9,16 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_gauge
`ScopeDroppedAttrCount` UInt32 CODEC(ZSTD(1)),
`ScopeSchemaUrl` String CODEC(ZSTD(1)),
`ServiceName` LowCardinality(String) CODEC(ZSTD(1)),
`MetricName` String CODEC(ZSTD(1)),
`MetricName` LowCardinality(String) CODEC(ZSTD(1)),

@knudtty knudtty Jun 29, 2026

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Changing to LowCardinality reduces PK memory usage by 2-3x

@iShiBin iShiBin Jun 30, 2026

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Seems to be a good change. I wonder why not apply it to the MetricName to all other metrics tables?

@knudtty knudtty Jun 30, 2026

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Good callout. That was a mistake.

@iShiBin iShiBin Jun 30, 2026

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Glad it was addressed. thanks.

`MetricDescription` String CODEC(ZSTD(1)),
`MetricUnit` String CODEC(ZSTD(1)),
`Attributes` Map(LowCardinality(String), String) CODEC(ZSTD(1)),
`StartTimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`StartTimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
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`Value` Float64 CODEC(ZSTD(1)),
`Flags` UInt32 CODEC(ZSTD(1)),
`Exemplars.FilteredAttributes` Array(Map(LowCardinality(String), String)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime64(9)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime) CODEC(ZSTD(1)),
Comment on lines -16 to +21

@knudtty knudtty Jun 29, 2026

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Second precision is an appropriate default and reduces the storage unit from 8 bytes -> 4 bytes

`Exemplars.Value` Array(Float64) CODEC(ZSTD(1)),
`Exemplars.SpanId` Array(String) CODEC(ZSTD(1)),
`Exemplars.TraceId` Array(String) CODEC(ZSTD(1)),
Expand All @@ -27,11 +27,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_gauge
INDEX idx_scope_attr_key mapKeys(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_scope_attr_value mapValues(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_key mapKeys(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_time_minmax TimeUnix TYPE minmax GRANULARITY 1
Comment on lines -30 to +31

@knudtty knudtty Jun 29, 2026

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minmax is an extremely lightweight index and helps efficiently prune granules, even if the PK is not fully qualified for a query to take advantage of TimeUnix

)
ENGINE = MergeTree
PARTITION BY toDate(TimeUnix)
ORDER BY (ServiceName, MetricName, Attributes, toUnixTimestamp64Nano(TimeUnix))
ORDER BY (ServiceName, MetricName, toStartOfHour(TimeUnix), cityHash64(Attributes), TimeUnix)

@knudtty knudtty Jun 29, 2026

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Time bucketing before the high cardinality Attributes column groups data more efficiently speeding up I/O for queries due to less overall ranges and is very efficient in PK memory

Comment on lines -34 to +35

@knudtty knudtty Jun 29, 2026

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Hashing the Attributes column massively reduces PK memory

@iShiBin iShiBin Jun 30, 2026

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why is that? Is it because some attribute key or values are too long?

@knudtty knudtty Jun 30, 2026

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Yes, both the length of keys or values as well as the number in a single entry. Additionally, ClickHouse does well with known sized parameters, like the 64 bit hash value

@iShiBin iShiBin Jun 30, 2026

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Got it and thanks.

TTL toDateTime(TimeUnix) + ${TABLES_TTL}
SETTINGS ttl_only_drop_parts = 1;

Expand All @@ -50,12 +51,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_sum
`MetricDescription` String CODEC(ZSTD(1)),
`MetricUnit` String CODEC(ZSTD(1)),
`Attributes` Map(LowCardinality(String), String) CODEC(ZSTD(1)),
`StartTimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`StartTimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`Value` Float64 CODEC(ZSTD(1)),
`Flags` UInt32 CODEC(ZSTD(1)),
`Exemplars.FilteredAttributes` Array(Map(LowCardinality(String), String)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime64(9)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime) CODEC(ZSTD(1)),
`Exemplars.Value` Array(Float64) CODEC(ZSTD(1)),
`Exemplars.SpanId` Array(String) CODEC(ZSTD(1)),
`Exemplars.TraceId` Array(String) CODEC(ZSTD(1)),
Expand All @@ -66,11 +67,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_sum
INDEX idx_scope_attr_key mapKeys(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_scope_attr_value mapValues(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_key mapKeys(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_time_minmax TimeUnix TYPE minmax GRANULARITY 1
)
ENGINE = MergeTree
PARTITION BY toDate(TimeUnix)
ORDER BY (ServiceName, MetricName, Attributes, toUnixTimestamp64Nano(TimeUnix))
ORDER BY (ServiceName, MetricName, toStartOfHour(TimeUnix), cityHash64(Attributes), TimeUnix)
TTL toDateTime(TimeUnix) + ${TABLES_TTL}
SETTINGS ttl_only_drop_parts = 1;
-- +goose StatementEnd
Expand All @@ -90,14 +92,14 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_histogram
`MetricDescription` String CODEC(ZSTD(1)),
`MetricUnit` String CODEC(ZSTD(1)),
`Attributes` Map(LowCardinality(String), String) CODEC(ZSTD(1)),
`StartTimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`StartTimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`Count` UInt64 CODEC(Delta(8), ZSTD(1)),
`Sum` Float64 CODEC(ZSTD(1)),
`BucketCounts` Array(UInt64) CODEC(ZSTD(1)),
`ExplicitBounds` Array(Float64) CODEC(ZSTD(1)),
`Exemplars.FilteredAttributes` Array(Map(LowCardinality(String), String)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime64(9)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime) CODEC(ZSTD(1)),
`Exemplars.Value` Array(Float64) CODEC(ZSTD(1)),
`Exemplars.SpanId` Array(String) CODEC(ZSTD(1)),
`Exemplars.TraceId` Array(String) CODEC(ZSTD(1)),
Expand All @@ -110,11 +112,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_histogram
INDEX idx_scope_attr_key mapKeys(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_scope_attr_value mapValues(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_key mapKeys(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_time_minmax TimeUnix TYPE minmax GRANULARITY 1
)
ENGINE = MergeTree
PARTITION BY toDate(TimeUnix)
ORDER BY (ServiceName, MetricName, Attributes, toUnixTimestamp64Nano(TimeUnix))
ORDER BY (ServiceName, MetricName, toStartOfHour(TimeUnix), cityHash64(Attributes), TimeUnix)
TTL toDateTime(TimeUnix) + ${TABLES_TTL}
SETTINGS ttl_only_drop_parts = 1;
-- +goose StatementEnd
Expand All @@ -134,8 +137,8 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_exponential_histogram
`MetricDescription` String CODEC(ZSTD(1)),
`MetricUnit` String CODEC(ZSTD(1)),
`Attributes` Map(LowCardinality(String), String) CODEC(ZSTD(1)),
`StartTimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`StartTimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`Count` UInt64 CODEC(Delta(8), ZSTD(1)),
`Sum` Float64 CODEC(ZSTD(1)),
`Scale` Int32 CODEC(ZSTD(1)),
Expand All @@ -145,7 +148,7 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_exponential_histogram
`NegativeOffset` Int32 CODEC(ZSTD(1)),
`NegativeBucketCounts` Array(UInt64) CODEC(ZSTD(1)),
`Exemplars.FilteredAttributes` Array(Map(LowCardinality(String), String)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime64(9)) CODEC(ZSTD(1)),
`Exemplars.TimeUnix` Array(DateTime) CODEC(ZSTD(1)),
`Exemplars.Value` Array(Float64) CODEC(ZSTD(1)),
`Exemplars.SpanId` Array(String) CODEC(ZSTD(1)),
`Exemplars.TraceId` Array(String) CODEC(ZSTD(1)),
Expand All @@ -158,11 +161,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_exponential_histogram
INDEX idx_scope_attr_key mapKeys(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_scope_attr_value mapValues(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_key mapKeys(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_time_minmax TimeUnix TYPE minmax GRANULARITY 1
)
ENGINE = MergeTree
PARTITION BY toDate(TimeUnix)
ORDER BY (ServiceName, MetricName, Attributes, toUnixTimestamp64Nano(TimeUnix))
ORDER BY (ServiceName, MetricName, toStartOfHour(TimeUnix), cityHash64(Attributes), TimeUnix)
TTL toDateTime(TimeUnix) + ${TABLES_TTL}
SETTINGS ttl_only_drop_parts = 1;
-- +goose StatementEnd
Expand All @@ -182,8 +186,8 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_summary
`MetricDescription` String CODEC(ZSTD(1)),
`MetricUnit` String CODEC(ZSTD(1)),
`Attributes` Map(LowCardinality(String), String) CODEC(ZSTD(1)),
`StartTimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime64(9) CODEC(Delta(8), ZSTD(1)),
`StartTimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`TimeUnix` DateTime CODEC(Delta(8), ZSTD(1)),
`Count` UInt64 CODEC(Delta(8), ZSTD(1)),
`Sum` Float64 CODEC(ZSTD(1)),
`ValueAtQuantiles.Quantile` Array(Float64) CODEC(ZSTD(1)),
Expand All @@ -194,11 +198,12 @@ CREATE TABLE IF NOT EXISTS ${DATABASE}.otel_metrics_summary
INDEX idx_scope_attr_key mapKeys(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_scope_attr_value mapValues(ScopeAttributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_key mapKeys(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1
INDEX idx_attr_value mapValues(Attributes) TYPE bloom_filter(0.01) GRANULARITY 1,
INDEX idx_time_minmax TimeUnix TYPE minmax GRANULARITY 1
)
ENGINE = MergeTree
PARTITION BY toDate(TimeUnix)
ORDER BY (ServiceName, MetricName, Attributes, toUnixTimestamp64Nano(TimeUnix))
ORDER BY (ServiceName, MetricName, toStartOfHour(TimeUnix), cityHash64(Attributes), TimeUnix)
TTL toDateTime(TimeUnix) + ${TABLES_TTL}
SETTINGS ttl_only_drop_parts = 1;
-- +goose StatementEnd
Expand Down
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