chore: change where tag module is instantiated

pkg/modules/tag/impltag/module.go

@@ -0,0 +1,57 @@
+package impltag
+
+import (
+	"context"
+
+	"github.com/SigNoz/signoz/pkg/modules/tag"
+	"github.com/SigNoz/signoz/pkg/types/tagtypes"
+	"github.com/SigNoz/signoz/pkg/valuer"
+)
+
+type module struct {
+	store tagtypes.Store
+}
+
+func NewModule(store tagtypes.Store) tag.Module {
+	return &module{store: store}
+}
+
+func (m *module) CreateMany(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, postable []tagtypes.PostableTag, createdBy string) ([]*tagtypes.Tag, error) {
+	if len(postable) == 0 {
+		return []*tagtypes.Tag{}, nil
+	}
+
+	toCreate, matched, err := tagtypes.Resolve(ctx, m.store, orgID, entityType, postable, createdBy)
+	if err != nil {
+		return nil, err
+	}
+
+	created, err := m.store.Create(ctx, toCreate)
+	if err != nil {
+		return nil, err
+	}
+
+	return append(matched, created...), nil
+}
+
+func (m *module) LinkToEntity(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, entityID valuer.UUID, tagIDs []valuer.UUID) error {
+	if len(tagIDs) == 0 {
+		return nil
+	}
+	return m.store.CreateRelations(ctx, tagtypes.NewTagRelations(orgID, entityType, entityID, tagIDs))
+}
+
+func (m *module) SyncLinksForEntity(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, entityID valuer.UUID, tagIDs []valuer.UUID) error {
+	if err := m.store.CreateRelations(ctx, tagtypes.NewTagRelations(orgID, entityType, entityID, tagIDs)); err != nil {
+		return err
+	}
+	return m.store.DeleteRelationsExcept(ctx, entityType, entityID, tagIDs)
+}
+
+func (m *module) ListForEntity(ctx context.Context, entityType tagtypes.EntityType, entityID valuer.UUID) ([]*tagtypes.Tag, error) {
+	return m.store.ListByEntity(ctx, entityType, entityID)
+}
+
+func (m *module) ListForEntities(ctx context.Context, entityType tagtypes.EntityType, entityIDs []valuer.UUID) (map[valuer.UUID][]*tagtypes.Tag, error) {
+	return m.store.ListByEntities(ctx, entityType, entityIDs)
+}

pkg/modules/tag/impltag/store.go

@@ -0,0 +1,132 @@
+package impltag
+
+import (
+	"context"
+
+	"github.com/SigNoz/signoz/pkg/sqlstore"
+	"github.com/SigNoz/signoz/pkg/types/tagtypes"
+	"github.com/SigNoz/signoz/pkg/valuer"
+	"github.com/uptrace/bun"
+)
+
+type store struct {
+	sqlstore sqlstore.SQLStore
+}
+
+func NewStore(sqlstore sqlstore.SQLStore) tagtypes.Store {
+	return &store{sqlstore: sqlstore}
+}
+
+func (s *store) List(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType) ([]*tagtypes.Tag, error) {
+	tags := make([]*tagtypes.Tag, 0)
+	err := s.sqlstore.
+		BunDBCtx(ctx).
+		NewSelect().
+		Model(&tags).
+		Where("org_id = ?", orgID).
+		Where("entity_type = ?", entityType).
+		Scan(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return tags, nil
+}
+
+func (s *store) ListByEntity(ctx context.Context, entityType tagtypes.EntityType, entityID valuer.UUID) ([]*tagtypes.Tag, error) {
+	tags := make([]*tagtypes.Tag, 0)
+	err := s.sqlstore.
+		BunDBCtx(ctx).
+		NewSelect().
+		Model(&tags).
+		Join("JOIN tag_relations AS tr ON tr.tag_id = tag.id").
+		Where("tr.entity_type = ?", entityType).
+		Where("tr.entity_id = ?", entityID).
+		Scan(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return tags, nil
+}
+
+func (s *store) ListByEntities(ctx context.Context, entityType tagtypes.EntityType, entityIDs []valuer.UUID) (map[valuer.UUID][]*tagtypes.Tag, error) {
+	if len(entityIDs) == 0 {
+		return map[valuer.UUID][]*tagtypes.Tag{}, nil
+	}
+
+	type joinedRow struct {
+		tagtypes.Tag
+		EntityID valuer.UUID `bun:"entity_id"`
+	}
+
+	rows := make([]*joinedRow, 0)
+	err := s.sqlstore.
+		BunDBCtx(ctx).
+		NewSelect().
+		Model(&rows).
+		ColumnExpr("tag.*, tr.entity_id").
+		Join("JOIN tag_relations AS tr ON tr.tag_id = tag.id").
+		Where("tr.entity_type = ?", entityType).
+		Where("tr.entity_id IN (?)", bun.In(entityIDs)).
+		Scan(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	out := make(map[valuer.UUID][]*tagtypes.Tag)
+	for _, r := range rows {
+		tag := r.Tag
+		out[r.EntityID] = append(out[r.EntityID], &tag)
+	}
+	return out, nil
+}
+
+func (s *store) Create(ctx context.Context, tags []*tagtypes.Tag) ([]*tagtypes.Tag, error) {
+	if len(tags) == 0 {
+		return tags, nil
+	}
+	// DO UPDATE on a self-set is a deliberate no-op write whose only purpose
+	// is to make RETURNING fire on conflicting rows. Without it, RETURNING is
+	// silent on the conflict path and we'd have to refetch by (key, value) to
+	// learn the existing rows' IDs after a concurrent-insert race. Setting
+	// key = tag.key (the existing row's value) preserves the first writer's
+	// casing on case-only collisions.
+	err := s.sqlstore.
+		BunDBCtx(ctx).
+		NewInsert().
+		Model(&tags).
+		On("CONFLICT (org_id, entity_type, (LOWER(key)), (LOWER(value))) DO UPDATE").
+		Set("key = tag.key").
+		Returning("*").
+		Scan(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return tags, nil
+}
+
+func (s *store) CreateRelations(ctx context.Context, relations []*tagtypes.TagRelation) error {
+	if len(relations) == 0 {
+		return nil
+	}
+	_, err := s.sqlstore.
+		BunDBCtx(ctx).
+		NewInsert().
+		Model(&relations).
+		On("CONFLICT (entity_type, entity_id, tag_id) DO NOTHING").
+		Exec(ctx)
+	return err
+}
+
+func (s *store) DeleteRelationsExcept(ctx context.Context, entityType tagtypes.EntityType, entityID valuer.UUID, keepTagIDs []valuer.UUID) error {
+	q := s.sqlstore.
+		BunDBCtx(ctx).
+		NewDelete().
+		Model((*tagtypes.TagRelation)(nil)).
+		Where("entity_type = ?", entityType).
+		Where("entity_id = ?", entityID)
+	if len(keepTagIDs) > 0 {
+		q = q.Where("tag_id NOT IN (?)", bun.In(keepTagIDs))
+	}
+	_, err := q.Exec(ctx)
+	return err
+}

pkg/modules/tag/impltag/store_test.go

@@ -0,0 +1,146 @@
+package impltag
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/SigNoz/signoz/pkg/factory/factorytest"
+	"github.com/SigNoz/signoz/pkg/sqlstore"
+	"github.com/SigNoz/signoz/pkg/sqlstore/sqlitesqlstore"
+	"github.com/SigNoz/signoz/pkg/types/tagtypes"
+	"github.com/SigNoz/signoz/pkg/valuer"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/uptrace/bun"
+)
+
+func newTestStore(t *testing.T) sqlstore.SQLStore {
+	t.Helper()
+	dbPath := filepath.Join(t.TempDir(), "test.db")
+	store, err := sqlitesqlstore.New(context.Background(), factorytest.NewSettings(), sqlstore.Config{
+		Provider: "sqlite",
+		Connection: sqlstore.ConnectionConfig{
+			MaxOpenConns:    1,
+			MaxConnLifetime: 0,
+		},
+		Sqlite: sqlstore.SqliteConfig{
+			Path:            dbPath,
+			Mode:            "wal",
+			BusyTimeout:     5 * time.Second,
+			TransactionMode: "deferred",
+		},
+	})
+	require.NoError(t, err)
+
+	_, err = store.BunDB().NewCreateTable().
+		Model((*tagtypes.Tag)(nil)).
+		IfNotExists().
+		Exec(context.Background())
+	require.NoError(t, err)
+
+	_, err = store.BunDB().Exec(`CREATE UNIQUE INDEX IF NOT EXISTS uq_tag_org_entity_lower_key_lower_value ON tag (org_id, entity_type, LOWER(key), LOWER(value))`)
+	require.NoError(t, err)
+	return store
+}
+
+var dashboardEntityType = tagtypes.MustNewEntityType("dashboard")
+
+func tagsByLowerKeyValue(t *testing.T, db *bun.DB) map[string]*tagtypes.Tag {
+	t.Helper()
+	all := make([]*tagtypes.Tag, 0)
+	require.NoError(t, db.NewSelect().Model(&all).Scan(context.Background()))
+	out := map[string]*tagtypes.Tag{}
+	for _, tag := range all {
+		out[strings.ToLower(tag.Key)+"\x00"+strings.ToLower(tag.Value)] = tag
+	}
+	return out
+}
+
+func TestStore_Create_PopulatesIDsOnFreshInsert(t *testing.T) {
+	ctx := context.Background()
+	sqlstore := newTestStore(t)
+	s := NewStore(sqlstore)
+
+	orgID := valuer.GenerateUUID()
+	tagA := tagtypes.NewTag(orgID, dashboardEntityType, "tag", "Database", "u@signoz.io")
+	tagB := tagtypes.NewTag(orgID, dashboardEntityType, "team", "BLR", "u@signoz.io")
+	preIDA := tagA.ID
+	preIDB := tagB.ID
+
+	got, err := s.Create(ctx, []*tagtypes.Tag{tagA, tagB})
+	require.NoError(t, err)
+	require.Len(t, got, 2)
+
+	// No race → pre-generated IDs stand. The slice is what we passed in,
+	// confirming Scan didn't reallocate.
+	assert.Equal(t, preIDA, got[0].ID)
+	assert.Equal(t, preIDB, got[1].ID)
+
+	// And the rows are in the DB.
+	stored := tagsByLowerKeyValue(t, sqlstore.BunDB())
+	require.Contains(t, stored, "tag\x00database")
+	require.Contains(t, stored, "team\x00blr")
+	assert.Equal(t, preIDA, stored["tag\x00database"].ID)
+	assert.Equal(t, preIDB, stored["team\x00blr"].ID)
+}
+
+func TestStore_Create_ConflictReturnsExistingRowID(t *testing.T) {
+	ctx := context.Background()
+	sqlstore := newTestStore(t)
+	s := NewStore(sqlstore)
+
+	orgID := valuer.GenerateUUID()
+
+	// Simulate a concurrent insert: someone else has already inserted "tag:Database".
+	winner := tagtypes.NewTag(orgID, dashboardEntityType, "tag", "Database", "concurrent")
+	_, err := s.Create(ctx, []*tagtypes.Tag{winner})
+	require.NoError(t, err)
+	winnerID := winner.ID
+
+	// Now our request runs with a different pre-generated ID for the same
+	// (key, value) — case differs but the functional unique index collapses
+	// them. RETURNING should overwrite our stale ID with winner's ID.
+	loser := tagtypes.NewTag(orgID, dashboardEntityType, "TAG", "DATABASE", "u@signoz.io")
+	loserPreID := loser.ID
+	require.NotEqual(t, winnerID, loserPreID, "pre-generated IDs must differ for this test to be meaningful")
+
+	got, err := s.Create(ctx, []*tagtypes.Tag{loser})
+	require.NoError(t, err)
+	require.Len(t, got, 1)
+
+	assert.Equal(t, winnerID, got[0].ID, "returned slice should carry the existing row's ID, not our stale one")
+	assert.Equal(t, winnerID, loser.ID, "input slice element is mutated in place")
+
+	// And the DB still has exactly one row for that (lower(key), lower(value)) — winner's, with winner's casing.
+	stored := tagsByLowerKeyValue(t, sqlstore.BunDB())
+	require.Len(t, stored, 1)
+	assert.Equal(t, winnerID, stored["tag\x00database"].ID)
+	assert.Equal(t, "tag", stored["tag\x00database"].Key, "winner's casing preserved in key")
+	assert.Equal(t, "Database", stored["tag\x00database"].Value, "winner's casing preserved in value")
+}
+
+func TestStore_Create_MixedFreshAndConflict(t *testing.T) {
+	ctx := context.Background()
+	sqlstore := newTestStore(t)
+	s := NewStore(sqlstore)
+
+	orgID := valuer.GenerateUUID()
+	pre := tagtypes.NewTag(orgID, dashboardEntityType, "tag", "Database", "concurrent")
+	_, err := s.Create(ctx, []*tagtypes.Tag{pre})
+	require.NoError(t, err)
+	preExistingID := pre.ID
+
+	conflict := tagtypes.NewTag(orgID, dashboardEntityType, "tag", "Database", "u@signoz.io")
+	fresh := tagtypes.NewTag(orgID, dashboardEntityType, "team", "BLR", "u@signoz.io")
+	freshPreID := fresh.ID
+
+	got, err := s.Create(ctx, []*tagtypes.Tag{conflict, fresh})
+	require.NoError(t, err)
+	require.Len(t, got, 2)
+
+	assert.Equal(t, preExistingID, got[0].ID, "conflicting row's ID overwritten with the existing row's")
+	assert.Equal(t, freshPreID, got[1].ID, "fresh row's pre-generated ID is preserved")
+}

pkg/modules/tag/tag.go

@@ -0,0 +1,24 @@
+package tag
+
+import (
+	"context"
+
+	"github.com/SigNoz/signoz/pkg/types/tagtypes"
+	"github.com/SigNoz/signoz/pkg/valuer"
+)
+
+type Module interface {
+	// Does not link the resolved tags to any entity — call LinkToEntity for that.
+	CreateMany(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, postable []tagtypes.PostableTag, createdBy string) ([]*tagtypes.Tag, error)
+
+	// Existing rows are left untouched.
+	LinkToEntity(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, entityID valuer.UUID, tagIDs []valuer.UUID) error
+
+	// missing links are inserted, obsolete ones removed.
+	SyncLinksForEntity(ctx context.Context, orgID valuer.UUID, entityType tagtypes.EntityType, entityID valuer.UUID, tagIDs []valuer.UUID) error
+
+	ListForEntity(ctx context.Context, entityType tagtypes.EntityType, entityID valuer.UUID) ([]*tagtypes.Tag, error)
+
+	// Entities with no tags are absent from the returned map.
+	ListForEntities(ctx context.Context, entityType tagtypes.EntityType, entityIDs []valuer.UUID) (map[valuer.UUID][]*tagtypes.Tag, error)
+}

pkg/signoz/handler_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/SigNoz/signoz/pkg/instrumentation/instrumentationtest"
 	"github.com/SigNoz/signoz/pkg/modules/dashboard/impldashboard"
 	"github.com/SigNoz/signoz/pkg/modules/organization/implorganization"
+	"github.com/SigNoz/signoz/pkg/modules/tag/impltag"
 	"github.com/SigNoz/signoz/pkg/modules/user/impluser"
 	"github.com/SigNoz/signoz/pkg/querier"
 	"github.com/SigNoz/signoz/pkg/queryparser"
@@ -44,6 +45,7 @@ func TestNewHandlers(t *testing.T) {
 	emailing := emailingtest.New()
 	queryParser := queryparser.New(providerSettings)
 	require.NoError(t, err)
+	tagModule := impltag.NewModule(impltag.NewStore(sqlstore))
 	dashboardModule := impldashboard.NewModule(impldashboard.NewStore(sqlstore), providerSettings, nil, orgGetter, queryParser)
 
 	flagger, err := flagger.New(context.Background(), instrumentationtest.New().ToProviderSettings(), flagger.Config{}, flagger.MustNewRegistry())
@@ -52,7 +54,7 @@ func TestNewHandlers(t *testing.T) {
 	userRoleStore := impluser.NewUserRoleStore(sqlstore, providerSettings)
 
 	userGetter := impluser.NewGetter(impluser.NewStore(sqlstore, providerSettings), userRoleStore, flagger)
-	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, nil, nil, nil, nil, nil, nil, nil, queryParser, Config{}, dashboardModule, userGetter, userRoleStore, nil, nil, flagger)
+	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, nil, nil, nil, nil, nil, nil, nil, queryParser, Config{}, dashboardModule, userGetter, userRoleStore, nil, nil, flagger, tagModule)
 
 	querierHandler := querier.NewHandler(providerSettings, nil, nil)
 	registryHandler := factory.NewHandler(nil)

pkg/signoz/module.go

@@ -40,6 +40,7 @@ import (
 	"github.com/SigNoz/signoz/pkg/modules/session/implsession"
 	"github.com/SigNoz/signoz/pkg/modules/spanpercentile"
 	"github.com/SigNoz/signoz/pkg/modules/spanpercentile/implspanpercentile"
+	"github.com/SigNoz/signoz/pkg/modules/tag"
 	"github.com/SigNoz/signoz/pkg/modules/tracedetail"
 	"github.com/SigNoz/signoz/pkg/modules/tracedetail/impltracedetail"
 	"github.com/SigNoz/signoz/pkg/modules/tracefunnel"
@@ -80,6 +81,7 @@ type Modules struct {
 	CloudIntegration cloudintegration.Module
 	RuleStateHistory rulestatehistory.Module
 	TraceDetail      tracedetail.Module
+	Tag              tag.Module
 }
 
 func NewModules(
@@ -104,6 +106,7 @@ func NewModules(
 	serviceAccount serviceaccount.Module,
 	cloudIntegrationModule cloudintegration.Module,
 	fl flagger.Flagger,
+	tagModule tag.Module,
 ) Modules {
 	quickfilter := implquickfilter.NewModule(implquickfilter.NewStore(sqlstore))
 	orgSetter := implorganization.NewSetter(implorganization.NewStore(sqlstore), alertmanager, quickfilter)
@@ -133,5 +136,6 @@ func NewModules(
 		RuleStateHistory: implrulestatehistory.NewModule(implrulestatehistory.NewStore(telemetryStore, telemetryMetadataStore, providerSettings.Logger)),
 		CloudIntegration: cloudIntegrationModule,
 		TraceDetail:      impltracedetail.NewModule(impltracedetail.NewTraceStore(telemetryStore), providerSettings, config.TraceDetail),
+		Tag:              tagModule,
 	}
 }

pkg/signoz/module_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/SigNoz/signoz/pkg/modules/organization/implorganization"
 	"github.com/SigNoz/signoz/pkg/modules/serviceaccount"
 	"github.com/SigNoz/signoz/pkg/modules/serviceaccount/implserviceaccount"
+	"github.com/SigNoz/signoz/pkg/modules/tag/impltag"
 	"github.com/SigNoz/signoz/pkg/modules/user/impluser"
 	"github.com/SigNoz/signoz/pkg/queryparser"
 	"github.com/SigNoz/signoz/pkg/sharder"
@@ -45,6 +46,7 @@ func TestNewModules(t *testing.T) {
 	emailing := emailingtest.New()
 	queryParser := queryparser.New(providerSettings)
 	require.NoError(t, err)
+	tagModule := impltag.NewModule(impltag.NewStore(sqlstore))
 	dashboardModule := impldashboard.NewModule(impldashboard.NewStore(sqlstore), providerSettings, nil, orgGetter, queryParser)
 
 	flagger, err := flagger.New(context.Background(), instrumentationtest.New().ToProviderSettings(), flagger.Config{}, flagger.MustNewRegistry())
@@ -56,7 +58,7 @@ func TestNewModules(t *testing.T) {
 
 	serviceAccount := implserviceaccount.NewModule(implserviceaccount.NewStore(sqlstore), nil, nil, nil, providerSettings, serviceaccount.Config{})
 
-	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, nil, nil, nil, nil, nil, nil, nil, queryParser, Config{}, dashboardModule, userGetter, userRoleStore, serviceAccount, implcloudintegration.NewModule(), flagger)
+	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, nil, nil, nil, nil, nil, nil, nil, queryParser, Config{}, dashboardModule, userGetter, userRoleStore, serviceAccount, implcloudintegration.NewModule(), flagger, tagModule)
 
 	reflectVal := reflect.ValueOf(modules)
 	for i := 0; i < reflectVal.NumField(); i++ {

pkg/signoz/provider.go

@@ -196,6 +196,7 @@ func NewSQLMigrationProviderFactories(
 		sqlmigration.NewDropUserDeletedAtFactory(sqlstore, sqlschema),
 		sqlmigration.NewMigrateAWSAllRegionsFactory(sqlstore),
 		sqlmigration.NewAddServiceAccountManagedRoleTransactionsFactory(sqlstore),
+		sqlmigration.NewAddTagsFactory(sqlstore, sqlschema),
 	)
 }
 

pkg/signoz/signoz.go

@@ -29,6 +29,7 @@ import (
 	"github.com/SigNoz/signoz/pkg/modules/rulestatehistory"
 	"github.com/SigNoz/signoz/pkg/modules/serviceaccount"
 	"github.com/SigNoz/signoz/pkg/modules/serviceaccount/implserviceaccount"
+	"github.com/SigNoz/signoz/pkg/modules/tag/impltag"
 	"github.com/SigNoz/signoz/pkg/modules/user/impluser"
 	"github.com/SigNoz/signoz/pkg/prometheus"
 	"github.com/SigNoz/signoz/pkg/querier"
@@ -325,6 +326,11 @@ func New(
 	// Initialize query parser (needed for dashboard module)
 	queryParser := queryparser.New(providerSettings)
 
+	// Initialize tag module — shared across modules that link entities to tags
+	// (currently dashboard; future: alerts, RBAC). Built once here and injected
+	// where needed.
+	tagModule := impltag.NewModule(impltag.NewStore(sqlstore))
+
 	// Initialize dashboard module
 	dashboard := dashboardModuleCallback(sqlstore, providerSettings, analytics, orgGetter, queryParser, querier, licensing)
 
@@ -441,7 +447,7 @@ func New(
 	}
 
 	// Initialize all modules
-	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, analytics, querier, telemetrystore, telemetryMetadataStore, authNs, authz, cache, queryParser, config, dashboard, userGetter, userRoleStore, serviceAccount, cloudIntegrationModule, flagger)
+	modules := NewModules(sqlstore, tokenizer, emailing, providerSettings, orgGetter, alertmanager, analytics, querier, telemetrystore, telemetryMetadataStore, authNs, authz, cache, queryParser, config, dashboard, userGetter, userRoleStore, serviceAccount, cloudIntegrationModule, flagger, tagModule)
 
 	// Initialize ruler from the variant-specific provider factories
 	rulerInstance, err := factory.NewProviderFromNamedMap(ctx, providerSettings, config.Ruler, rulerProviderFactories(cache, alertmanager, sqlstore, telemetrystore, telemetryMetadataStore, prometheus, orgGetter, modules.RuleStateHistory, querier, queryParser), "signoz")

pkg/sqlmigration/079_add_tags.go

@@ -0,0 +1,102 @@
+package sqlmigration
+
+import (
+	"context"
+
+	"github.com/SigNoz/signoz/pkg/factory"
+	"github.com/SigNoz/signoz/pkg/sqlschema"
+	"github.com/SigNoz/signoz/pkg/sqlstore"
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/migrate"
+)
+
+type addTags struct {
+	sqlstore  sqlstore.SQLStore
+	sqlschema sqlschema.SQLSchema
+}
+
+func NewAddTagsFactory(sqlstore sqlstore.SQLStore, sqlschema sqlschema.SQLSchema) factory.ProviderFactory[SQLMigration, Config] {
+	return factory.NewProviderFactory(factory.MustNewName("add_tags"), func(ctx context.Context, ps factory.ProviderSettings, c Config) (SQLMigration, error) {
+		return &addTags{
+			sqlstore:  sqlstore,
+			sqlschema: sqlschema,
+		}, nil
+	})
+}
+
+func (migration *addTags) Register(migrations *migrate.Migrations) error {
+	return migrations.Register(migration.Up, migration.Down)
+}
+
+func (migration *addTags) Up(ctx context.Context, db *bun.DB) error {
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		_ = tx.Rollback()
+	}()
+
+	sqls := [][]byte{}
+
+	tagTableSQLs := migration.sqlschema.Operator().CreateTable(&sqlschema.Table{
+		Name: "tag",
+		Columns: []*sqlschema.Column{
+			{Name: "id", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "key", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "value", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "org_id", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "entity_type", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "created_at", DataType: sqlschema.DataTypeTimestamp, Nullable: false},
+			{Name: "created_by", DataType: sqlschema.DataTypeText, Nullable: true},
+			{Name: "updated_at", DataType: sqlschema.DataTypeTimestamp, Nullable: false},
+			{Name: "updated_by", DataType: sqlschema.DataTypeText, Nullable: true},
+		},
+		PrimaryKeyConstraint: &sqlschema.PrimaryKeyConstraint{ColumnNames: []sqlschema.ColumnName{"id"}},
+		ForeignKeyConstraints: []*sqlschema.ForeignKeyConstraint{
+			{
+				ReferencingColumnName: sqlschema.ColumnName("org_id"),
+				ReferencedTableName:   sqlschema.TableName("organizations"),
+				ReferencedColumnName:  sqlschema.ColumnName("id"),
+			},
+		},
+	})
+	sqls = append(sqls, tagTableSQLs...)
+
+	// Functional unique index: case-insensitive uniqueness on (org_id, entity_type, key, value).
+	// sqlschema.UniqueIndex doesn't support expressions, so emit raw SQL — both
+	// Postgres and SQLite (modernc 3.50.x) support expression indexes.
+	sqls = append(sqls, []byte(`CREATE UNIQUE INDEX IF NOT EXISTS uq_tag_org_entity_lower_key_lower_value ON tag (org_id, entity_type, LOWER(key), LOWER(value))`))
+
+	tagRelationsTableSQLs := migration.sqlschema.Operator().CreateTable(&sqlschema.Table{
+		Name: "tag_relations",
+		Columns: []*sqlschema.Column{
+			{Name: "entity_type", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "entity_id", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "tag_id", DataType: sqlschema.DataTypeText, Nullable: false},
+			{Name: "org_id", DataType: sqlschema.DataTypeText, Nullable: false},
+		},
+		PrimaryKeyConstraint: &sqlschema.PrimaryKeyConstraint{ColumnNames: []sqlschema.ColumnName{"entity_type", "entity_id", "tag_id"}},
+		ForeignKeyConstraints: []*sqlschema.ForeignKeyConstraint{
+			{
+				ReferencingColumnName: sqlschema.ColumnName("org_id"),
+				ReferencedTableName:   sqlschema.TableName("organizations"),
+				ReferencedColumnName:  sqlschema.ColumnName("id"),
+			},
+		},
+	})
+	sqls = append(sqls, tagRelationsTableSQLs...)
+
+	for _, sql := range sqls {
+		if _, err := tx.ExecContext(ctx, string(sql)); err != nil {
+			return err
+		}
+	}
+
+	return tx.Commit()
+}
+
+func (migration *addTags) Down(_ context.Context, _ *bun.DB) error {
+	return nil
+}

pkg/types/tagtypes/store.go

@@ -0,0 +1,27 @@
+package tagtypes
+
+import (
+	"context"
+
+	"github.com/SigNoz/signoz/pkg/valuer"
+)
+
+type Store interface {
+	List(ctx context.Context, orgID valuer.UUID, entityType EntityType) ([]*Tag, error)
+
+	ListByEntity(ctx context.Context, entityType EntityType, entityID valuer.UUID) ([]*Tag, error)
+
+	ListByEntities(ctx context.Context, entityType EntityType, entityIDs []valuer.UUID) (map[valuer.UUID][]*Tag, error)
+
+	// Create upserts the given tags and returns them with authoritative IDs.
+	// On conflict on (org_id, entity_type, LOWER(key), LOWER(value)) — which
+	// happens only when a concurrent insert raced ours, including casing-only
+	// collisions — the returned entry carries the existing row's ID rather
+	// than the pre-generated one in the input.
+	Create(ctx context.Context, tags []*Tag) ([]*Tag, error)
+
+	// CreateRelations inserts tag-entity relations. Conflicts on the composite primary key are ignored.
+	CreateRelations(ctx context.Context, relations []*TagRelation) error
+
+	DeleteRelationsExcept(ctx context.Context, entityType EntityType, entityID valuer.UUID, keepTagIDs []valuer.UUID) error
+}

pkg/types/tagtypes/tag.go

@@ -0,0 +1,137 @@
+package tagtypes
+
+import (
+	"context"
+	"strings"
+	"time"
+
+	"github.com/SigNoz/signoz/pkg/errors"
+	"github.com/SigNoz/signoz/pkg/types"
+	"github.com/SigNoz/signoz/pkg/valuer"
+	"github.com/uptrace/bun"
+)
+
+var (
+	ErrCodeTagInvalidName = errors.MustNewCode("tag_invalid_name")
+	ErrCodeTagNotFound    = errors.MustNewCode("tag_not_found")
+)
+
+type Tag struct {
+	bun.BaseModel `bun:"table:tag,alias:tag"`
+
+	types.Identifiable
+	types.TimeAuditable
+	types.UserAuditable
+	Key        string      `json:"key" required:"true" bun:"key,type:text,notnull"`
+	Value      string      `json:"value" required:"true" bun:"value,type:text,notnull"`
+	OrgID      valuer.UUID `json:"orgId" required:"true" bun:"org_id,type:text,notnull"`
+	EntityType EntityType  `json:"entityType" required:"true" bun:"entity_type,type:text,notnull"`
+}
+
+type PostableTag struct {
+	Key   string `json:"key" required:"true"`
+	Value string `json:"value" required:"true"`
+}
+
+type GettableTag = PostableTag
+
+func NewGettableTagFromTag(tag *Tag) *GettableTag {
+	return &GettableTag{Key: tag.Key, Value: tag.Value}
+}
+
+func NewGettableTagsFromTags(tags []*Tag) []*GettableTag {
+	out := make([]*GettableTag, len(tags))
+	for i, t := range tags {
+		out[i] = NewGettableTagFromTag(t)
+	}
+	return out
+}
+
+func NewTag(orgID valuer.UUID, entityType EntityType, key, value, createdBy string) *Tag {
+	now := time.Now()
+	return &Tag{
+		Identifiable: types.Identifiable{ID: valuer.GenerateUUID()},
+		TimeAuditable: types.TimeAuditable{
+			CreatedAt: now,
+			UpdatedAt: now,
+		},
+		UserAuditable: types.UserAuditable{
+			CreatedBy: createdBy,
+			UpdatedBy: createdBy,
+		},
+		Key:        key,
+		Value:      value,
+		OrgID:      orgID,
+		EntityType: entityType,
+	}
+}
+
+// Resolve canonicalizes a batch of user-supplied (key, value) tag pairs against
+// the existing tags for an org. Lookup is case-insensitive on both key and
+// value (matching the storage uniqueness rule); when an existing row matches,
+// its display casing is reused. Inputs are deduped on (LOWER(key), LOWER(value));
+// the first input's casing wins on collisions. Returns:
+//   - toCreate: new Tag rows the caller should insert (with pre-generated IDs)
+//   - matched: existing rows the caller's input already pointed to. They
+//     already carry authoritative IDs from the store.
+func Resolve(ctx context.Context, store Store, orgID valuer.UUID, entityType EntityType, postable []PostableTag, createdBy string) ([]*Tag, []*Tag, error) {
+	if len(postable) == 0 {
+		return nil, nil, nil
+	}
+
+	existing, err := store.List(ctx, orgID, entityType)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	lowercaseTagsMap := make(map[string]*Tag, len(existing))
+	for _, t := range existing {
+		mapKey := strings.ToLower(t.Key) + "\x00" + strings.ToLower(t.Value)
+		lowercaseTagsMap[mapKey] = t
+	}
+
+	seenInRequestAlready := make(map[string]struct{}, len(postable)) // postable can have the same tag multiple times
+	toCreate := make([]*Tag, 0)
+	matched := make([]*Tag, 0)
+
+	for _, p := range postable {
+		key, value, err := validatePostableTag(p)
+		if err != nil {
+			return nil, nil, err
+		}
+		lookup := strings.ToLower(key) + "\x00" + strings.ToLower(value)
+		if _, dup := seenInRequestAlready[lookup]; dup {
+			continue
+		}
+		seenInRequestAlready[lookup] = struct{}{}
+
+		if existingTag, ok := lowercaseTagsMap[lookup]; ok {
+			matched = append(matched, existingTag)
+			continue
+		}
+		toCreate = append(toCreate, NewTag(orgID, entityType, key, value, createdBy))
+	}
+
+	return toCreate, matched, nil
+}
+
+// Entity-specific reserved-key checks (e.g. dashboard column names that would
+// collide with the list-query DSL) are the caller's responsibility — perform
+// them before calling into the tag module.
+func validatePostableTag(p PostableTag) (string, string, error) {
+	key := strings.TrimSpace(p.Key)
+	value := strings.TrimSpace(p.Value)
+	if key == "" {
+		return "", "", errors.Newf(errors.TypeInvalidInput, ErrCodeTagInvalidName, "tag key cannot be empty")
+	}
+	if value == "" {
+		return "", "", errors.Newf(errors.TypeInvalidInput, ErrCodeTagInvalidName, "tag value cannot be empty")
+	}
+	if strings.ContainsRune(key, '/') {
+		return "", "", errors.Newf(errors.TypeInvalidInput, ErrCodeTagInvalidName, "tag key %q cannot contain '/'", key)
+	}
+	if strings.ContainsRune(value, '/') {
+		return "", "", errors.Newf(errors.TypeInvalidInput, ErrCodeTagInvalidName, "tag value %q cannot contain '/'", value)
+	}
+	return key, value, nil
+}

pkg/types/tagtypes/tag_relation.go

@@ -0,0 +1,38 @@
+package tagtypes
+
+import (
+	"github.com/SigNoz/signoz/pkg/valuer"
+	"github.com/uptrace/bun"
+)
+
+type EntityType struct{ valuer.String }
+
+func MustNewEntityType(name string) EntityType {
+	return EntityType{valuer.NewString(name)}
+}
+
+type TagRelation struct {
+	bun.BaseModel `bun:"table:tag_relations,alias:tag_relations"`
+
+	EntityType EntityType  `json:"entityType" required:"true" bun:"entity_type,type:text,notnull"`
+	EntityID   valuer.UUID `json:"entityId" required:"true" bun:"entity_id,pk,type:text,notnull"`
+	TagID      valuer.UUID `json:"tagId" required:"true" bun:"tag_id,pk,type:text,notnull"`
+	OrgID      valuer.UUID `json:"orgId" required:"true" bun:"org_id,type:text,notnull"`
+}
+
+func NewTagRelation(orgID valuer.UUID, entityType EntityType, entityID valuer.UUID, tagID valuer.UUID) *TagRelation {
+	return &TagRelation{
+		EntityType: entityType,
+		EntityID:   entityID,
+		TagID:      tagID,
+		OrgID:      orgID,
+	}
+}
+
+func NewTagRelations(orgID valuer.UUID, entityType EntityType, entityID valuer.UUID, tagIDs []valuer.UUID) []*TagRelation {
+	relations := make([]*TagRelation, 0, len(tagIDs))
+	for _, tagID := range tagIDs {
+		relations = append(relations, NewTagRelation(orgID, entityType, entityID, tagID))
+	}
+	return relations
+}

pkg/types/tagtypes/tag_test.go

@@ -0,0 +1,166 @@
+package tagtypes
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/SigNoz/signoz/pkg/valuer"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestValidatePostableTag(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     PostableTag
+		wantKey   string
+		wantValue string
+		wantError bool
+	}{
+		{name: "simple pair", input: PostableTag{Key: "team", Value: "pulse"}, wantKey: "team", wantValue: "pulse"},
+		{name: "preserves casing", input: PostableTag{Key: "Team", Value: "Pulse"}, wantKey: "Team", wantValue: "Pulse"},
+		{name: "trims key", input: PostableTag{Key: "  team  ", Value: "pulse"}, wantKey: "team", wantValue: "pulse"},
+		{name: "trims value", input: PostableTag{Key: "team", Value: "  pulse  "}, wantKey: "team", wantValue: "pulse"},
+
+		{name: "empty key rejected", input: PostableTag{Key: "", Value: "pulse"}, wantError: true},
+		{name: "empty value rejected", input: PostableTag{Key: "team", Value: ""}, wantError: true},
+		{name: "whitespace-only key rejected", input: PostableTag{Key: "   ", Value: "pulse"}, wantError: true},
+		{name: "whitespace-only value rejected", input: PostableTag{Key: "team", Value: "   "}, wantError: true},
+
+		{name: "slash in key rejected", input: PostableTag{Key: "team/eng", Value: "pulse"}, wantError: true},
+		{name: "slash in value rejected", input: PostableTag{Key: "team", Value: "pulse/events"}, wantError: true},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			gotKey, gotValue, err := validatePostableTag(tc.input)
+			if tc.wantError {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			assert.Equal(t, tc.wantKey, gotKey)
+			assert.Equal(t, tc.wantValue, gotValue)
+		})
+	}
+}
+
+var testEntityType = MustNewEntityType("dashboard")
+
+type fakeStore struct {
+	tags          []*Tag
+	listCallCount int
+}
+
+func (f *fakeStore) List(_ context.Context, _ valuer.UUID, _ EntityType) ([]*Tag, error) {
+	f.listCallCount++
+	out := make([]*Tag, len(f.tags))
+	copy(out, f.tags)
+	return out, nil
+}
+
+func (f *fakeStore) Create(_ context.Context, tags []*Tag) ([]*Tag, error) {
+	return tags, nil
+}
+
+func (f *fakeStore) CreateRelations(_ context.Context, _ []*TagRelation) error {
+	return nil
+}
+
+func (f *fakeStore) ListByEntity(_ context.Context, _ EntityType, _ valuer.UUID) ([]*Tag, error) {
+	return []*Tag{}, nil
+}
+
+func (f *fakeStore) ListByEntities(_ context.Context, _ EntityType, _ []valuer.UUID) (map[valuer.UUID][]*Tag, error) {
+	return map[valuer.UUID][]*Tag{}, nil
+}
+
+func (f *fakeStore) DeleteRelationsExcept(_ context.Context, _ EntityType, _ valuer.UUID, _ []valuer.UUID) error {
+	return nil
+}
+
+func TestResolve(t *testing.T) {
+	t.Run("empty input does not hit store", func(t *testing.T) {
+		store := &fakeStore{}
+		toCreate, matched, err := Resolve(context.Background(), store, valuer.GenerateUUID(), testEntityType, nil, "u@signoz.io")
+		require.NoError(t, err)
+		assert.Empty(t, toCreate)
+		assert.Empty(t, matched)
+		assert.Zero(t, store.listCallCount, "should not hit store when input is empty")
+	})
+
+	t.Run("creates missing pairs and reuses existing", func(t *testing.T) {
+		orgID := valuer.GenerateUUID()
+		dbTag := NewTag(orgID, testEntityType, "team", "Pulse", "seed")
+		dbTag2 := NewTag(orgID, testEntityType, "Database", "redis", "seed")
+		store := &fakeStore{tags: []*Tag{dbTag, dbTag2}}
+
+		toCreate, matched, err := Resolve(context.Background(), store, orgID, testEntityType, []PostableTag{
+			{Key: "team", Value: "events"},    // new
+			{Key: "DATABASE", Value: "REDIS"}, // case-only conflict
+			{Key: "Brand", Value: "New"},      // new
+		}, "u@signoz.io")
+		require.NoError(t, err)
+
+		createdLowerKVs := []string{}
+		for _, tg := range toCreate {
+			createdLowerKVs = append(createdLowerKVs, strings.ToLower(tg.Key)+"\x00"+strings.ToLower(tg.Value))
+		}
+		assert.ElementsMatch(t, []string{"team\x00events", "brand\x00new"}, createdLowerKVs,
+			"only the two missing pairs should be returned for insertion")
+
+		require.Len(t, matched, 1, "DATABASE:REDIS should hit the existing 'Database:redis' tag")
+		assert.Same(t, dbTag2, matched[0], "matched should return the existing pointer with its authoritative ID")
+	})
+
+	t.Run("dedupes inputs that map to the same lower(key)+lower(value)", func(t *testing.T) {
+		orgID := valuer.GenerateUUID()
+		store := &fakeStore{}
+
+		toCreate, matched, err := Resolve(context.Background(), store, orgID, testEntityType, []PostableTag{
+			{Key: "Foo", Value: "Bar"},
+			{Key: "foo", Value: "bar"},
+			{Key: "FOO", Value: "BAR"},
+		}, "u@signoz.io")
+		require.NoError(t, err)
+
+		require.Empty(t, matched)
+		require.Len(t, toCreate, 1, "duplicate inputs must collapse into a single insert")
+		assert.Equal(t, "Foo", toCreate[0].Key, "first input's casing wins")
+		assert.Equal(t, "Bar", toCreate[0].Value, "first input's casing wins")
+	})
+
+	t.Run("preserves existing casing on case-only match", func(t *testing.T) {
+		orgID := valuer.GenerateUUID()
+		dbTag := NewTag(orgID, testEntityType, "Team", "Pulse", "seed")
+		store := &fakeStore{tags: []*Tag{dbTag}}
+
+		toCreate, matched, err := Resolve(context.Background(), store, orgID, testEntityType, []PostableTag{
+			{Key: "team", Value: "PULSE"},
+		}, "u@signoz.io")
+		require.NoError(t, err)
+
+		assert.Empty(t, toCreate)
+		require.Len(t, matched, 1)
+		assert.Equal(t, "Team", matched[0].Key)
+		assert.Equal(t, "Pulse", matched[0].Value)
+	})
+
+	t.Run("propagates validation error from any input", func(t *testing.T) {
+		store := &fakeStore{}
+		_, _, err := Resolve(context.Background(), store, valuer.GenerateUUID(), testEntityType, []PostableTag{
+			{Key: "team", Value: "pulse"},
+			{Key: "", Value: "x"},
+		}, "u@signoz.io")
+		require.Error(t, err)
+	})
+
+	t.Run("propagates slash validation error", func(t *testing.T) {
+		store := &fakeStore{}
+		_, _, err := Resolve(context.Background(), store, valuer.GenerateUUID(), testEntityType, []PostableTag{
+			{Key: "team/eng", Value: "pulse"},
+		}, "u@signoz.io")
+		require.Error(t, err)
+		assert.True(t, strings.Contains(err.Error(), "/"), "error should reference the disallowed character")
+	})
+}