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Merge pull request #15445 from rynkat/update-docs-anchored-regex

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docs: make it clearer that regexps are always fully anchored
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Björn Rabenstein 2024-11-27 20:52:29 +01:00 committed by GitHub
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15
docs/querying/basics.md
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@ -37,7 +37,7 @@ Depending on the use-case (e.g. when graphing vs. displaying the output of an
expression), only some of these types are legal as the result of a expression), only some of these types are legal as the result of a
user-specified expression. user-specified expression.
For [instant queries](api.md#instant-queries), any of the above data types are allowed as the root of the expression. For [instant queries](api.md#instant-queries), any of the above data types are allowed as the root of the expression.
[Range queries](api.md/#range-queries) only support scalar-typed and instant-vector-typed expressions. [Range queries](api.md#range-queries) only support scalar-typed and instant-vector-typed expressions.
_Notes about the experimental native histograms:_ _Notes about the experimental native histograms:_
@ -152,7 +152,7 @@ The value returned will be that of the most recent sample at or before the
query's evaluation timestamp (in the case of an query's evaluation timestamp (in the case of an
[instant query](api.md#instant-queries)) [instant query](api.md#instant-queries))
or the current step within the query (in the case of a or the current step within the query (in the case of a
[range query](api.md/#range-queries)). [range query](api.md#range-queries)).
The [`@` modifier](#modifier) allows overriding the timestamp relative to which The [`@` modifier](#modifier) allows overriding the timestamp relative to which
the selection takes place. Time series are only returned if their most recent sample is less than the [lookback period](#staleness) ago. the selection takes place. Time series are only returned if their most recent sample is less than the [lookback period](#staleness) ago.
@ -178,7 +178,7 @@ against regular expressions. The following label matching operators exist:
* `=~`: Select labels that regex-match the provided string. * `=~`: Select labels that regex-match the provided string.
* `!~`: Select labels that do not regex-match the provided string. * `!~`: Select labels that do not regex-match the provided string.
Regex matches are fully anchored. A match of `env=~"foo"` is treated as `env=~"^foo$"`. [Regex](#regular-expressions) matches are fully anchored. A match of `env=~"foo"` is treated as `env=~"^foo$"`.
For example, this selects all `http_requests_total` time series for `staging`, For example, this selects all `http_requests_total` time series for `staging`,
`testing`, and `development` environments and HTTP methods other than `GET`. `testing`, and `development` environments and HTTP methods other than `GET`.
@ -241,9 +241,6 @@ A workaround for this restriction is to use the `__name__` label:
{__name__="on"} # Good! {__name__="on"} # Good!
All regular expressions in Prometheus use [RE2
syntax](https://github.com/google/re2/wiki/Syntax).
### Range Vector Selectors ### Range Vector Selectors
Range vector literals work like instant vector literals, except that they Range vector literals work like instant vector literals, except that they
@ -365,6 +362,12 @@ PromQL supports line comments that start with `#`. Example:
# This is a comment # This is a comment
## Regular expressions
All regular expressions in Prometheus use [RE2 syntax](https://github.com/google/re2/wiki/Syntax).
Regex matches are always fully anchored.
## Gotchas ## Gotchas
### Staleness ### Staleness

5
docs/querying/examples.md
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@ -25,14 +25,11 @@ for the same vector, making it a [range vector](../basics/#range-vector-selector
Note that an expression resulting in a range vector cannot be graphed directly, Note that an expression resulting in a range vector cannot be graphed directly,
but viewed in the tabular ("Console") view of the expression browser. but viewed in the tabular ("Console") view of the expression browser.
Using regular expressions, you could select time series only for jobs whose Using [regular expressions](./basics.md#regular-expressions), you could select time series only for jobs whose
name match a certain pattern, in this case, all jobs that end with `server`: name match a certain pattern, in this case, all jobs that end with `server`:
http_requests_total{job=~".*server"} http_requests_total{job=~".*server"}
All regular expressions in Prometheus use [RE2
syntax](https://github.com/google/re2/wiki/Syntax).
To select all HTTP status codes except 4xx ones, you could run: To select all HTTP status codes except 4xx ones, you could run:
http_requests_total{status!~"4.."} http_requests_total{status!~"4.."}

2
docs/querying/functions.md
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@ -598,7 +598,7 @@ label_join(up{job="api-server",src1="a",src2="b",src3="c"}, "foo", ",", "src1",
## `label_replace()` ## `label_replace()`
For each timeseries in `v`, `label_replace(v instant-vector, dst_label string, replacement string, src_label string, regex string)` For each timeseries in `v`, `label_replace(v instant-vector, dst_label string, replacement string, src_label string, regex string)`
matches the [regular expression](https://github.com/google/re2/wiki/Syntax) `regex` against the value of the label `src_label`. If it matches the [regular expression](./basics.md#regular-expressions) `regex` against the value of the label `src_label`. If it
matches, the value of the label `dst_label` in the returned timeseries will be the expansion matches, the value of the label `dst_label` in the returned timeseries will be the expansion
of `replacement`, together with the original labels in the input. Capturing groups in the of `replacement`, together with the original labels in the input. Capturing groups in the
regular expression can be referenced with `$1`, `$2`, etc. Named capturing groups in the regular expression can be referenced with `$name` (where `name` is the capturing group name). If the regular expression doesn't match then the timeseries is returned unchanged. regular expression can be referenced with `$1`, `$2`, etc. Named capturing groups in the regular expression can be referenced with `$name` (where `name` is the capturing group name). If the regular expression doesn't match then the timeseries is returned unchanged.