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Add testcase for promql blog
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‎testcases/promqltest/blog_example_1.test‎

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# Run this with:
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#
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# git clone https://github.com/prometheus/prometheus
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# cd prometheus
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#
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# then copy it into ./promql/promqltest/testdata/blog_example_1.test
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#
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# and run:
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#
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# go test -v -run 'TestEvaluations/testdata/blog_example_1.test' --count=1 ./promql
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load 1m
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requests_total{instance="foo", endpoint="/api/v1/status"} 1000x5
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requests_total{instance="foo", endpoint="/api/v1/query"} 2000x5
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requests_total{instance="bar", endpoint="/api/v1/status"} 2500x5
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requests_total{instance="ownermissing", endpoint="/api/v1/status"} 3000x5
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component_price_multiplier{instance="foo", owner="internaluser1"} 1x5
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component_price_multiplier{instance="bar", owner="ushealthcare"} 20x5
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component_price_multiplier{instance="baz", owner="idleandunused"} 0x5
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# 1:1 label matching; fails because requests_total{instance="foo"} has 2 matching series on LHS
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eval instant at 1m requests_total{} * on (instance) (component_price_multiplier)
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expect fail msg:multiple matches for labels: many-to-one matching must be explicit (group_left/group_right)
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# 1:m matching; fails because requests_total{instance="foo"} has 2 matching series on LHS
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#
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# Fails with
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#
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# found duplicate series for the match group {instance="foo"} on the left hand-side of the operation: [{__name__="requests_total", endpoint="/api/v1/query", instance="foo"}, {__name__="requests_total", endpoint="/api/v1/status", instance="foo"}];many-to-many matching not allowed: matching labels must be unique on one side
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#
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eval instant at 1m requests_total{} * on (instance) group_right(owner) (component_price_multiplier)
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expect fail regex:found duplicate series for the match group \{instance="foo"\} on the left hand-side of the operation: \[.*\];many-to-many matching not allowed: matching labels must be unique on one side
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# n:1 matching
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#
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# Works; acts like an inner join, dropping the unmatched requests_total{instance="ownermissing"} series
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#
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eval instant at 1m requests_total{} * on (instance) group_left(owner) (component_price_multiplier)
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{endpoint="/api/v1/status", instance="foo", owner="internaluser1"} 1000
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{endpoint="/api/v1/query", instance="foo", owner="internaluser1"} 2000
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{endpoint="/api/v1/status", instance="bar", owner="ushealthcare"} 50000
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# n:1 matching with unmatched values kept (emulated LEFT JOIN)
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#
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# Works. The * 1 is just there to drop the __name__ label.
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#
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eval instant at 1m requests_total{} * on (instance) group_left(owner) (component_price_multiplier) or on (instance) (requests_total{} * 1)
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{endpoint="/api/v1/status", instance="foo", owner="internaluser1"} 1000
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{endpoint="/api/v1/query", instance="foo", owner="internaluser1"} 2000
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{endpoint="/api/v1/status", instance="bar", owner="ushealthcare"} 50000
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{endpoint="/api/v1/status", instance="ownermissing"} 3000
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# -------------------
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# Some extras
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# -------------------
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# Now what if we introduce duplication into the RHS? Now there are two different
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# series matching component_price_multiplier{instance="foo"}, one with a subcategory set
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load 1m
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component_price_multiplier{instance="foo", subcategory="discount", owner="internaluser1"} 0.9x5
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# Fails with an error because the RHS is non-unique on (instance) now
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# found duplicate series for the match group {instance="foo"} on the right hand-side of the operation: [{__name__="component_price_multiplier", instance="foo", owner="internaluser1", subcategory="discount"}, {__name__="component_price_multiplier", instance="foo", owner="internaluser1"}];many-to-many matching not allowed: matching labels must be unique on one side
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#
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eval instant at 1m requests_total{} * on (instance) group_left(owner) (component_price_multiplier)
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expect fail regex:found duplicate series for the match group \{instance="foo"\} on the right hand-side of the operation: \[.*\];many-to-many matching not allowed: matching labels must be unique on one side
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# Adding subcategory to the join condition worked; a missing label is treated as "" so
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# the RHS with subcategory didn't match any LHS rows and was filtered out.
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eval instant at 1m requests_total{} * on (instance, subcategory) group_left(owner) (component_price_multiplier)
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{endpoint="/api/v1/status", instance="foo", owner="internaluser1"} 1000
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{endpoint="/api/v1/query", instance="foo", owner="internaluser1"} 2000
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{endpoint="/api/v1/status", instance="bar", owner="ushealthcare"} 50000

‎testcases/promqltest/sql_equivalent.psql‎

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-- PostgreSQL-flavoured SQL
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CREATE TABLE metrics(labels jsonb, value float8);
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INSERT INTO metrics(labels, value)
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VALUES
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('{"__name__": "requests_total", "instance": "foo", "endpoint": "/api/v1/status"}', 1000),
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('{"__name__": "requests_total", "instance": "foo", "endpoint": "/api/v1/query"}', 2000),
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('{"__name__": "requests_total", "instance": "bar", "endpoint": "/api/v1/status"}', 2500),
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('{"__name__": "requests_total", "instance": "ownermissing", "endpoint": "/api/v1/status"}', 3000);
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INSERT INTO metrics(labels, value)
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VALUES
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('{"__name__": "component_price_multiplier", "instance": "foo", "owner": "internaluser1"}', 1),
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('{"__name__": "component_price_multiplier", "instance": "bar", "owner": "ushealthcare"}', 20),
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('{"__name__": "component_price_multiplier", "instance":"baz", "owner":"idleandunused"}', 0);
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-- For convenient reference to specific metric series
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CREATE VIEW requests_total AS
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SELECT * FROM metrics WHERE labels ->> '__name__' = 'requests_total';
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CREATE VIEW component_price_multiplier AS
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SELECT * FROM metrics WHERE labels ->> '__name__' = 'component_price_multiplier';
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-- Like:
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--
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-- requests_total{}
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-- * on (instance)
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-- group_left(owner)
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-- component_price_multiplier{}
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SELECT
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jsonb_insert(
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-- take all LHS labels
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requests_total.labels,
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-- add owner label from RHS
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ARRAY['owner'], component_price_multiplier.labels -> 'owner'
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) AS labels,
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-- apply arithmetic on value
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requests_total.value * component_price_multiplier.value AS value
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FROM requests_total
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-- keep rows for which a LHS and RHS match exists
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INNER JOIN component_price_multiplier ON (
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requests_total.labels ->> 'instance' = component_price_multiplier.labels ->> 'instance'
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);
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-- Result:
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-- labels | value
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-- -----------------------------------------------------------------------------------------------------------+-------
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "foo"} | 1000
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/query", "instance": "foo"} | 2000
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-- {"owner": "ushealthcare", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "bar"} | 50000
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-- (3 rows)
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-- Now as a left join so we keep the unmatched LHS. Note the coalesce(...) for the value, because
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-- lhs.value * rhs.value is null if the rhs is null in a left join.
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SELECT
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coalesce(
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-- if RHS matched, we can return a result with the owner label
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jsonb_insert(
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-- take all LHS labels
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requests_total.labels,
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-- add owner label from RHS
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ARRAY['owner'], component_price_multiplier.labels -> 'owner'
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),
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-- otherwise, we return the LHS labels unchanged
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requests_total.labels
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) AS labels,
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coalesce(
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-- if lhs and rhs did not match the rhs here is null, so
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requests_total.value * component_price_multiplier.value,
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-- pick the lhs if so
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requests_total.value
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) AS value
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FROM requests_total
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-- keep all LHS rows, add RHS fields only where LHS and RHS match, otherwise
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-- RHS fields will be null
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LEFT JOIN component_price_multiplier ON (
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requests_total.labels ->> 'instance' = component_price_multiplier.labels ->> 'instance'
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);
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-- Result:
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--
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-- labels | value
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-- -----------------------------------------------------------------------------------------------------------+-------
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "foo"} | 1000
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/query", "instance": "foo"} | 2000
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-- {"owner": "ushealthcare", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "bar"} | 50000
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-- {"__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "ownermissing"} | 3000
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-- (4 rows)
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-- Add the extra component_price_multiplier{instance="foo"} row with extra subcategory="discount" label
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INSERT INTO metrics(labels, value)
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VALUES
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('{"__name__": "component_price_multiplier", "instance": "foo", "subcategory": "discount", "owner": "internaluser1"}', 0.9);
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-- and repeat the first query
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SELECT
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-- take all LHS labels, add 'owner' label from RHS
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jsonb_insert(requests_total.labels, ARRAY['owner'], component_price_multiplier.labels -> 'owner') AS labels,
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-- apply arithmetic on value
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requests_total.value * component_price_multiplier.value AS value
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FROM requests_total
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-- keep rows for which a LHS and RHS match exists
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INNER JOIN component_price_multiplier ON (
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requests_total.labels ->> 'instance' = component_price_multiplier.labels ->> 'instance'
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);
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-- result: duplicate series (which would not be allowed in PromQL, resulting in an error)
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--
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-- labels | value
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-- -----------------------------------------------------------------------------------------------------------+-------
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "foo"} | 900
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "foo"} | 1000
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/query", "instance": "foo"} | 1800
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/query", "instance": "foo"} | 2000
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-- {"owner": "ushealthcare", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "bar"} | 50000
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-- (5 rows)
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-- We can correct this by adding subcategory to the join conditions
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SELECT
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-- take all LHS labels, add 'owner' label from RHS
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jsonb_insert(requests_total.labels, ARRAY['owner'], component_price_multiplier.labels -> 'owner') AS labels,
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-- apply arithmetic on value
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requests_total.value * component_price_multiplier.value AS value
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FROM requests_total
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-- keep rows for which a LHS and RHS match exists
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INNER JOIN component_price_multiplier ON (
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requests_total.labels ->> 'instance' = component_price_multiplier.labels ->> 'instance'
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AND
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-- Here we need to treat NULL = 'non-null' as false, not null, hence IS DISTINCT FROM instead of =
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requests_total.labels ->> 'subcategory' IS NOT DISTINCT FROM component_price_multiplier.labels ->> 'subcategory'
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);
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-- result:
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-- labels | value
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-- -----------------------------------------------------------------------------------------------------------+-------
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "foo"} | 1000
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-- {"owner": "internaluser1", "__name__": "requests_total", "endpoint": "/api/v1/query", "instance": "foo"} | 2000
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-- {"owner": "ushealthcare", "__name__": "requests_total", "endpoint": "/api/v1/status", "instance": "bar"} | 50000
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-- (3 rows)
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