Add CountDistinct finisher

CHANGELOG.md

@@ -4,6 +4,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic
 Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- `CountDistinct` finisher to count the distinct values of a column (`COUNT(DISTINCT column)`).
+
 ## [4.19.7] - 2025-12-31
 
 ### Fixed

README.md

@@ -1356,6 +1356,7 @@ models.Pilots().All(ctx, db)
 One() // Retrieve one row as object (same as LIMIT(1))
 All() // Retrieve all rows as objects (same as SELECT * FROM)
 Count() // Number of rows (same as COUNT(*))
+CountDistinct("name") // Number of distinct values in a column (same as COUNT(DISTINCT name))
 UpdateAll(models.M{"name": "John", "age": 23}) // Update all rows matching the built query.
 DeleteAll() // Delete all rows matching the built query.
 Exists() // Returns a bool indicating whether the row(s) for the built query exists.

templates/main/03_finishers.go.tpl

@@ -168,6 +168,60 @@ func (q {{$alias.DownSingular}}Query) Count({{if .NoContext}}exec boil.Executor{
 	return count, nil
 }
 
+{{if .AddGlobal -}}
+// CountDistinctG returns the count of distinct values of the given column in the query using the global executor.
+func (q {{$alias.DownSingular}}Query) CountDistinctG({{if not .NoContext}}ctx context.Context, {{end}}column string) (int64, error) {
+	return q.CountDistinct({{if .NoContext}}boil.GetDB(){{else}}ctx, boil.GetContextDB(){{end}}, column)
+}
+
+{{end -}}
+
+{{if and .AddGlobal .AddPanic -}}
+// CountDistinctGP returns the count of distinct values of the given column in the query using the global executor, and panics on error.
+func (q {{$alias.DownSingular}}Query) CountDistinctGP({{if not .NoContext}}ctx context.Context, {{end}}column string) int64 {
+	c, err := q.CountDistinct({{if .NoContext}}boil.GetDB(){{else}}ctx, boil.GetContextDB(){{end}}, column)
+	if err != nil {
+		panic(boil.WrapErr(err))
+	}
+
+	return c
+}
+
+{{end -}}
+
+{{if .AddPanic -}}
+// CountDistinctP returns the count of distinct values of the given column in the query, and panics on error.
+func (q {{$alias.DownSingular}}Query) CountDistinctP({{if .NoContext}}exec boil.Executor{{else}}ctx context.Context, exec boil.ContextExecutor{{end}}, column string) int64 {
+	c, err := q.CountDistinct({{if not .NoContext}}ctx, {{end -}} exec, column)
+	if err != nil {
+		panic(boil.WrapErr(err))
+	}
+
+	return c
+}
+
+{{end -}}
+
+// CountDistinct returns the count of distinct values of the given column in the query.
+func (q {{$alias.DownSingular}}Query) CountDistinct({{if .NoContext}}exec boil.Executor{{else}}ctx context.Context, exec boil.ContextExecutor{{end}}, column string) (int64, error) {
+	var count int64
+
+	queries.SetSelect(q.Query, nil)
+	queries.SetCount(q.Query)
+	queries.SetDistinct(q.Query, column)
+
+	{{if .NoContext -}}
+	err := q.Query.QueryRow(exec).Scan(&count)
+	{{else -}}
+	err := q.Query.QueryRowContext(ctx, exec).Scan(&count)
+	{{end -}}
+	if err != nil {
+		return 0, errors.Wrap(err, "{{.PkgName}}: failed to count distinct {{.Table.Name}} rows")
+	}
+
+	return count, nil
+}
+
 {{if .AddGlobal -}}
 // ExistsG checks if the row exists in the table using the global executor.
 func (q {{$alias.DownSingular}}Query) ExistsG({{if not .NoContext}}ctx context.Context{{end}}) (bool, error) {

templates/test/finishers.go.tpl

@@ -112,3 +112,38 @@ func test{{$alias.UpPlural}}Count(t *testing.T) {
 		t.Error("want 2 records, got:", count)
 	}
 }
+
+func test{{$alias.UpPlural}}CountDistinct(t *testing.T) {
+	t.Parallel()
+
+	var err error
+	seed := randomize.NewSeed()
+	{{$alias.DownSingular}}One := &{{$alias.UpSingular}}{}
+	{{$alias.DownSingular}}Two := &{{$alias.UpSingular}}{}
+	if err = randomize.Struct(seed, {{$alias.DownSingular}}One, {{$alias.DownSingular}}DBTypes, false, {{$alias.DownSingular}}ColumnsWithDefault...); err != nil {
+		t.Errorf("Unable to randomize {{$alias.UpSingular}} struct: %s", err)
+	}
+	if err = randomize.Struct(seed, {{$alias.DownSingular}}Two, {{$alias.DownSingular}}DBTypes, false, {{$alias.DownSingular}}ColumnsWithDefault...); err != nil {
+		t.Errorf("Unable to randomize {{$alias.UpSingular}} struct: %s", err)
+	}
+
+	{{if not .NoContext}}ctx := context.Background(){{end}}
+	tx := MustTx({{if .NoContext}}boil.Begin(){{else}}boil.BeginTx(ctx, nil){{end}})
+	defer func() { _ = tx.Rollback() }()
+	if err = {{$alias.DownSingular}}One.Insert({{if not .NoContext}}ctx, {{end -}} tx, boil.Infer()); err != nil {
+		t.Error(err)
+	}
+	if err = {{$alias.DownSingular}}Two.Insert({{if not .NoContext}}ctx, {{end -}} tx, boil.Infer()); err != nil {
+		t.Error(err)
+	}
+
+	// Two rows were inserted, so a distinct count of any single column is between 1 and 2.
+	count, err := {{$alias.UpPlural}}().CountDistinct({{if not .NoContext}}ctx, {{end -}} tx, "{{ (index $.Table.Columns 0).Name | $.Quotes }}")
+	if err != nil {
+		t.Error(err)
+	}
+
+	if count < 1 || count > 2 {
+		t.Error("want a distinct count between 1 and 2, got:", count)
+	}
+}

templates/test/singleton/boil_suites_test.go.tpl

@@ -142,6 +142,16 @@ func TestCount(t *testing.T) {
   {{- end -}}
 }
 
+func TestCountDistinct(t *testing.T) {
+  {{- range .Tables}}
+  {{- if or .IsJoinTable .IsView -}}
+  {{- else -}}
+  {{- $alias := $.Aliases.Table .Name -}}
+  t.Run("{{$alias.UpPlural}}", test{{$alias.UpPlural}}CountDistinct)
+  {{end -}}
+  {{- end -}}
+}
+
 {{if not .NoHooks -}}
 func TestHooks(t *testing.T) {
   {{- range .Tables}}