Corin Lawson 3fd1c2c0eb Introduce histogram support (#435) ... * Introduce histogram support Prior to this change, the custom queries were restricted to counters and gauges. This change introduces a new ColumnUsage, namely HISTOGRAM, that expects the column to contain an array of upper inclusive bounds for each observation bucket in the emitted metric. It also expects three more columns to be present with the suffixes: - `_bucket`, containing an array of cumulative counters for the observation buckets; - `_sum`, the total sum of all observed values; and - `_count`, the count of events that have been observed. A flag has been added to the MetricMap struct to easily identify metrics that should emit a histogram and the construction of a histogram metric is aided by the pg.Array function and a new helper dbToUint64 function. Finally, and example of usage is given in queries.yaml. fixes #402 Signed-off-by: Corin Lawson <corin@responsight.com> * Introduces tests for histogram support Prior to this change, the histogram support was untested. This change introduces a new integration test that reads a user query containing a number of histogram metrics. Also, additional checks have been added to TestBooleanConversionToValueAndString to test dbToUint64. Signed-off-by: Corin Lawson <corin@responsight.com>		2020-12-25 02:34:26 +11:00
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postgres_exporter	Introduce histogram support (#435)	2020-12-25 02:34:26 +11:00