lib/logstorage: allow using eval keyword instead of math keyword in math pipe

docs/VictoriaLogs/CHANGELOG.md

@@ -19,6 +19,8 @@ according to [these docs](https://docs.victoriametrics.com/victorialogs/quicksta
 
 ## tip
 
+* FEATURE: allow using `eval` instead of `math` keyword in [`math` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#math-pipe).
+
 ## [v0.17.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v0.17.0-victorialogs)
 
 Released at 2024-06-05

docs/VictoriaLogs/LogsQL.md

@@ -1681,10 +1681,25 @@ Every `argX` argument in every mathematical operation can contain one of the fol
 - Any [supported numeric value](#numeric-values), [rfc3339 time](https://www.rfc-editor.org/rfc/rfc3339) or IPv4 address. For example, `1MiB`, `"2024-05-15T10:20:30.934324Z"` or `"12.34.56.78"`.
 - Another mathematical expression, which can be put inside `(...)`. For example, `(a + b) * c`.
 
+The parsed time, duration and IPv4 address can be converted back to string representation after math transformations with the help of [`format` pipe](#format-pipe). For example,
+the following query rounds the `request_duration` [field](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model) to seconds before converting it back to string representation:
+
+```logsql
+_time:5m | math round(request_duration, 1e9) as request_duration_nsecs | format '<duration:request_duration_nsecs>' as request_duration
+```
+
+The `eval` keyword can be used instead of `math` for convenince. For example, the following query calculates `duration_msecs` field
+by multiplying `duration_secs` [field](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model) to `1000`:
+
+```logsql
+_time:5m | eval (duration_secs * 1000) as duration_msecs
+```
+
 See also:
 
 - [`stats` pipe](#stats-pipe)
 - [`extract` pipe](#extract-pipe)
+- [`format` pipe](#format-pipe)
 
 
 ### offset pipe

lib/logstorage/pipe.go

@@ -160,7 +160,7 @@ func parsePipe(lex *lexer) (pipe, error) {
 			return nil, fmt.Errorf("cannot parse 'limit' pipe: %w", err)
 		}
 		return pl, nil
-	case lex.isKeyword("math"):
+	case lex.isKeyword("math", "eval"):
 		pm, err := parsePipeMath(lex)
 		if err != nil {
 			return nil, fmt.Errorf("cannot parse 'math' pipe: %w", err)

lib/logstorage/pipe_math.go

@@ -356,8 +356,8 @@ func (pmp *pipeMathProcessor) flush() error {
 }
 
 func parsePipeMath(lex *lexer) (*pipeMath, error) {
-	if !lex.isKeyword("math") {
-		return nil, fmt.Errorf("unexpected token: %q; want %q", lex.token, "math")
+	if !lex.isKeyword("math", "eval") {
+		return nil, fmt.Errorf("unexpected token: %q; want 'math' or 'eval'", lex.token)
 	}
 	lex.nextToken()
 

lib/logstorage/pipe_math_test.go

@@ -77,7 +77,7 @@ func TestPipeMath(t *testing.T) {
 		},
 	})
 
-	f("math b+1 as a, a*2 as b, b-10.5+c as c", [][]Field{
+	f("eval b+1 as a, a*2 as b, b-10.5+c as c", [][]Field{
 		{
 			{"a", "v1"},
 			{"b", "2"},