From a53b5570eb7a9cc1659b79a4a3323ca90ab065ed Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Thu, 30 May 2024 14:37:21 +0200
Subject: [PATCH] wip

---
 docs/VictoriaLogs/CHANGELOG.md    |  1 +
 docs/VictoriaLogs/LogsQL.md       |  1 +
 lib/logstorage/pipe_math.go       | 16 +++++++++++++++
 lib/logstorage/pipe_math_test.go  | 34 +++++++++++++++++++++++++++++++
 lib/logstorage/pipe_stats_test.go |  6 +++---
 5 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/docs/VictoriaLogs/CHANGELOG.md b/docs/VictoriaLogs/CHANGELOG.md
index d02c15869..06b091313 100644
--- a/docs/VictoriaLogs/CHANGELOG.md
+++ b/docs/VictoriaLogs/CHANGELOG.md
@@ -19,6 +19,7 @@ according to [these docs](https://docs.victoriametrics.com/victorialogs/quicksta
 
 ## tip
 
+* FEATURE: add `default` operator to [`math` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#math-pipe). It allows setting `NaN` result to the given default value.
 * FEATURE: allow omitting result name in [`stats` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#stats-pipe). In this case the result name is automatically set to string representation of the corresponding [stats function expression](https://docs.victoriametrics.com/victorialogs/logsql/#stats-pipe-functions). For example, `_time:5m | count(*)` is valid [LogsQL query](https://docs.victoriametrics.com/victorialogs/logsql/) now. It is equivalent to `_time:5m | stats count(*) as "count(*)"`.
 
 * BUGFIX: properly calculate the number of matching rows in `* | field_values x | stats count() rows` and in `* | unroll (x) | stats count() rows` queries.
diff --git a/docs/VictoriaLogs/LogsQL.md b/docs/VictoriaLogs/LogsQL.md
index ea48a5e1c..6a0672c68 100644
--- a/docs/VictoriaLogs/LogsQL.md
+++ b/docs/VictoriaLogs/LogsQL.md
@@ -1608,6 +1608,7 @@ The following mathematical operations are supported by `math` pipe:
 - `arg1 / arg2` - divides `arg1` by `arg2`
 - `arg1 % arg2` - returns the remainder of the division of `arg1` by `arg2`
 - `arg1 ^ arg2` - returns the power of `arg1` by `arg2`
+- `arg1 default arg2` - returns `arg2` if `arg1` equals to `NaN`.
 - `abs(arg)` - returns an absolute value for the given `arg`
 - `max(arg1, ..., argN)` - returns the maximum value among the given `arg1`, ..., `argN`
 - `min(arg1, ..., argN)` - returns the minimum value among the given `arg1`, ..., `argN`
diff --git a/lib/logstorage/pipe_math.go b/lib/logstorage/pipe_math.go
index 07b66f446..5790ea07f 100644
--- a/lib/logstorage/pipe_math.go
+++ b/lib/logstorage/pipe_math.go
@@ -161,6 +161,10 @@ var mathBinaryOps = map[string]mathBinaryOp{
 		priority: 3,
 		f:        mathFuncMinus,
 	},
+	"default": {
+		priority: 10,
+		f:        mathFuncDefault,
+	},
 }
 
 type mathBinaryOp struct {
@@ -700,6 +704,18 @@ func mathFuncPow(result []float64, args [][]float64) {
 	}
 }
 
+func mathFuncDefault(result []float64, args [][]float64) {
+	values := args[0]
+	defaultValues := args[1]
+	for i := range result {
+		f := values[i]
+		if math.IsNaN(f) {
+			f = defaultValues[i]
+		}
+		result[i] = f
+	}
+}
+
 func mathFuncAbs(result []float64, args [][]float64) {
 	arg := args[0]
 	for i := range result {
diff --git a/lib/logstorage/pipe_math_test.go b/lib/logstorage/pipe_math_test.go
index 66a9da24f..af070a1a8 100644
--- a/lib/logstorage/pipe_math_test.go
+++ b/lib/logstorage/pipe_math_test.go
@@ -22,6 +22,7 @@ func TestParsePipeMathSuccess(t *testing.T) {
 	f(`math min(3, foo, (1 + bar) / baz) as a, max(a, b) as b, (abs(c) + 5) as d`)
 	f(`math round(foo) as x`)
 	f(`math round(foo, 0.1) as y`)
+	f(`math (a / b default 10) as z`)
 }
 
 func TestParsePipeMathFailure(t *testing.T) {
@@ -63,6 +64,39 @@ func TestPipeMath(t *testing.T) {
 		},
 	})
 
+	f("math a / b default 10 as c", [][]Field{
+		{
+			{"a", "v1"},
+			{"b", "2"},
+			{"c", "3"},
+		},
+		{
+			{"a", "0"},
+			{"b", "0"},
+			{"c", "3"},
+		},
+		{
+			{"a", "3"},
+			{"b", "2"},
+		},
+	}, [][]Field{
+		{
+			{"a", "v1"},
+			{"b", "2"},
+			{"c", "10"},
+		},
+		{
+			{"a", "0"},
+			{"b", "0"},
+			{"c", "10"},
+		},
+		{
+			{"a", "3"},
+			{"b", "2"},
+			{"c", "1.5"},
+		},
+	})
+
 	f("math 1 as a", [][]Field{
 		{
 			{"a", "v1"},
diff --git a/lib/logstorage/pipe_stats_test.go b/lib/logstorage/pipe_stats_test.go
index 5363518db..f6cab5fcf 100644
--- a/lib/logstorage/pipe_stats_test.go
+++ b/lib/logstorage/pipe_stats_test.go
@@ -39,8 +39,8 @@ func TestPipeStats(t *testing.T) {
 		expectPipeResults(t, pipeStr, rows, rowsExpected)
 	}
 
-	// missing 'stats' keyword
-	f("count(*) as rows", [][]Field{
+	// missing 'stats' keyword and resutl name
+	f("count(*)", [][]Field{
 		{
 			{"_msg", `abc`},
 			{"a", `2`},
@@ -56,7 +56,7 @@ func TestPipeStats(t *testing.T) {
 		},
 	}, [][]Field{
 		{
-			{"rows", "3"},
+			{`count(*)`, "3"},
 		},
 	})