VictoriaMetrics/docs/ExtendedPromQL.md

MetricsQL

VictoriaMetrics implements MetricsQL - query language inspired by PromQL. It is backwards compatible with PromQL, so Grafana dashboards backed by Prometheus datasource should work the same after switching from Prometheus to VictoriaMetrics. Standalone MetricsQL package can be used for parsing MetricsQL in external apps.

The following functionality is implemented differently in MetricsQL comparing to PromQL in order to improve user experience:

• MetricsQL takes into account the previous point before the window in square brackets for range functions such as rate and increase. It also doesn't extrapolate range function results. This addresses this issue from Prometheus.
• MetricsQL returns the expected non-empty responses for requests with step values smaller than scrape interval. This addresses this issue from Grafana.
• MetricsQL treats scalar type the same as instant vector without labels, since subtle difference between these types usually confuses users. See the corresponding Prometheus docs for details.

Other PromQL functionality should work the same in MetricsQL. File an issue if you notice discrepancies between PromQL and MetricsQL results other than mentioned above.

MetricsQL provides additional functionality mentioned below, which is aimed towards solving practical cases. Feel free filing a feature request if you think MetricsQL misses certain useful functionality.

Note that the functionality mentioned below doesn't work in PromQL, so it is impossible switching back to Prometheus after you start using it.

This functionality can be tried at an editable Grafana dashboard.

• WITH templates. This feature simplifies writing and managing complex queries. Go to WITH templates playground and try it.
• Metric names and metric labels may contain escaped chars. For instance, foo\-bar{baz\=aa="b"} is valid expression. It returns time series with name foo-bar containing label baz=aa with value b. Additionally, \xXX escape sequence is supported, where XX is hexadecimal representation of escaped char.
• offset, range duration and step value for range vector may refer to the current step aka $__interval value from Grafana. For instance, rate(metric[10i] offset 5i) would return per-second rate over a range covering 10 previous steps with the offset of 5 steps.
• offset may be put anywere in the query. For instance, sum(foo) offset 24h.
• offset may be negative. For example, q offset -1h.
• default binary operator. q1 default q2 substitutes NaN values from q1 with the corresponding values from q2.
• histogram_quantile accepts optional third arg - boundsLabel. In this case it returns lower and upper bounds for the estimated percentile. See this issue for details.
• if binary operator. q1 if q2 removes values from q1 for NaN values from q2.
• ifnot binary operator. q1 ifnot q2 removes values from q1 for non-NaN values from q2.
• Trailing commas on all the lists are allowed - label filters, function args and with expressions. For instance, the following queries are valid: m{foo="bar",}, f(a, b,), WITH (x=y,) x. This simplifies maintenance of multi-line queries.
• String literals may be concatenated. This is useful with WITH templates: WITH (commonPrefix="long_metric_prefix_") {__name__=commonPrefix+"suffix1"} / {__name__=commonPrefix+"suffix2"}.
• Range duration in functions such as rate may be omitted. VictoriaMetrics automatically selects range duration depending on the current step used for building the graph. For instance, the following query is valid in VictoriaMetrics: rate(node_network_receive_bytes_total).
• Range duration and offset may be fractional. For instance, rate(node_network_receive_bytes_total[1.5m] offset 0.5d).
• Comments starting with # and ending with newline. For instance, up # this is a comment for 'up' metric.
• Rollup functions - rollup(m[d]), rollup_rate(m[d]), rollup_deriv(m[d]), rollup_increase(m[d]), rollup_delta(m[d]) - return min, max and avg values for all the m data points over d duration.
• rollup_candlestick(m[d]) - returns open, close, low and high values (OHLC) for all the m data points over d duration. This function is useful for financial applications.
• union(q1, ... qN) function for building multiple graphs for q1, ... qN subqueries with a single query. The union function name may be skipped - the following queries are equivalent: union(q1, q2) and (q1, q2).
• ru(freeResources, maxResources) function for returning resource utilization percentage in the range 0% - 100%. For instance, ru(node_memory_MemFree_bytes, node_memory_MemTotal_bytes) returns memory utilization over node_exporter metrics.
• ttf(slowlyChangingFreeResources) function for returning the time in seconds when the given slowlyChangingFreeResources expression reaches zero. For instance, ttf(node_filesystem_avail_byte) returns the time to storage space exhaustion. This function may be useful for capacity planning.
• Functions for label manipulation:
  • alias(q, name) for setting metric name across all the time series q.
  • label_set(q, label1, value1, ... labelN, valueN) for setting the given values for the given labels on q.
  • label_del(q, label1, ... labelN) for deleting the given labels from q.
  • label_keep(q, label1, ... labelN) for deleting all the labels except the given labels from q.
  • label_copy(q, src_label1, dst_label1, ... src_labelN, dst_labelN) for copying label values from src_* to dst_*.
  • label_move(q, src_label1, dst_label1, ... src_labelN, dst_labelN) for moving label values from src_* to dst_*.
  • label_transform(q, label, regexp, replacement) for replacing all the regexp occurences with replacement in the label values from q.
  • label_value(q, label) - returns numeric values for the given label from q.
• step() function for returning the step in seconds used in the query.
• start() and end() functions for returning the start and end timestamps of the [start ... end] range used in the query.
• integrate(m[d]) for returning integral over the given duration d for the given metric m.
• ideriv(m) - for calculating instant derivative for m.
• deriv_fast(m[d]) - for calculating fast derivative for m based on the first and the last points from duration d.
• running_ functions - running_sum, running_min, running_max, running_avg - for calculating running values on the selected time range.
• range_ functions - range_sum, range_min, range_max, range_avg, range_first, range_last, range_median, range_quantile - for calculating global value over the selected time range.
• smooth_exponential(q, sf) - smooths q using exponential moving average with the given smooth factor sf.
• remove_resets(q) - removes counter resets from q.
• lag(q[d]) - returns lag between the current timestamp and the timestamp from the previous data point in q over d.
• lifetime(q[d]) - returns lifetime of q over d in seconds. It is expected that d exceeds the lifetime of q.
• scrape_interval(q[d]) - returns the average interval in seconds between data points of q over d aka scrape interval.
• Trigonometric functions - sin(q), cos(q), asin(q), acos(q) and pi().
• median_over_time(m[d]) - calculates median values for m over d time window. Shorthand to quantile_over_time(0.5, m[d]).
• median(q) - median aggregate. Shorthand to quantile(0.5, q).
• limitk(k, q) - limits the number of time series returned from q to k.
• keep_last_value(q) - fills missing data (gaps) in q with the previous value.
• distinct_over_time(m[d]) - returns distinct number of values for m data points over d duration.
• distinct(q) - returns a time series with the number of unique values for each timestamp in q.
• sum2_over_time(m[d]) - returns sum of squares for all the m values over d duration.
• sum2(q) - returns a time series with sum of square values for each timestamp in q.
• geomean_over_time(m[d]) - returns geomean value for all the m value over d duration.
• geomean(q) - returns a time series with geomean value for each timestamp in q.
• rand(), rand_normal() and rand_exponential() functions - for generating pseudo-random series with even, normal and exponential distribution.
• increases_over_time(m[d]) and decreases_over_time(m[d]) - returns the number of m increases or decreases over the given duration d.
• prometheus_buckets(q) - converts VictoriaMetrics histogram buckets to Prometheus buckets with le labels.
• histogram(q) - calculates aggregate histogram over q time series for each point on the graph. See this article for more details.
• histogram_over_time(m[d]) - calculates VictoriaMetrics histogram for m over d. For example, the following query calculates median temperature by country over the last 24 hours: histogram_quantile(0.5, sum(histogram_over_time(temperature[24h])) by (vmbucket, country)).
• histogram_share(le, buckets) - returns share (in the range 0..1) for buckets. Useful for calculating SLI and SLO. For instance, the following query returns the share of requests which are performed under 1.5 seconds: histogram_share(1.5, sum(request_duration_seconds_bucket) by (le)).
• topk_* and bottomk_* aggregate functions, which return up to K time series. Note that the standard topk function may return more than K time series - see this article for details.
  • topk_min(k, q) - returns top K time series with the max minimums on the given time range
  • topk_max(k, q) - returns top K time series with the max maximums on the given time range
  • topk_avg(k, q) - returns top K time series with the max averages on the given time range
  • topk_median(k, q) - returns top K time series with the max medians on the given time range
  • bottomk_min(k, q) - returns bottom K time series with the min minimums on the given time range
  • bottomk_max(k, q) - returns bottom K time series with the min maximums on the given time range
  • bottomk_avg(k, q) - returns bottom K time series with the min averages on the given time range
  • bottomk_median(k, q) - returns bottom K time series with the min medians on the given time range
• share_le_over_time(m[d], le) - returns share (in the range 0..1) of values in m over d, which are smaller or equal to le. Useful for calculating SLI and SLO. Example: share_le_over_time(memory_usage_bytes[24h], 100*1024*1024) returns the share of time series values for the last 24 hours when memory usage was below or equal to 100MB.
• share_gt_over_time(m[d], gt) - returns share (in the range 0..1) of values in m over d, which are bigger than gt. Useful for calculating SLI and SLO. Example: share_gt_over_time(up[24h], 0) - returns service availability for the last 24 hours.