[performance] overhaul struct (+ result) caching library for simplicity, performance and multiple-result lookups (#2535)

* rewrite cache library as codeberg.org/gruf/go-structr, implement in gotosocial

* use actual go-structr release version (not just commit hash)

* revert go toolchain changes (damn you go for auto changing this)

* fix go mod woes

* ensure %w is used in calls to errs.Appendf()

* fix error checking

* fix possible panic

* remove unnecessary start/stop functions, move to main Cache{} struct, add note regarding which caches require start/stop

* fix copy-paste artifact... :innocent:

* fix all comment copy-paste artifacts

* remove dropID() function, now we can just use slices.DeleteFunc()

* use util.Deduplicate() instead of collate(), move collate to util

* move orderByIDs() to util package and "generify"

* add a util.DeleteIf() function, use this to delete entries on failed population

* use slices.DeleteFunc() instead of util.DeleteIf() (i had the logic mixed up in my head somehow lol)

* add note about how collate differs from deduplicate

1 files changed, 51 insertions, 24 deletions

diff --git a/internal/db/bundb/tag.go b/internal/db/bundb/tag.go
index fac621f0a..66ee8cb3a 100644
--- a/internal/db/bundb/tag.go
+++ b/internal/db/bundb/tag.go
@@ -22,21 +22,21 @@ import (
 	"strings"
 
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
-	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/state"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
 	"github.com/uptrace/bun"
 )
 
 type tagDB struct {
-	conn  *DB
+	db    *DB
 	state *state.State
 }
 
-func (m *tagDB) GetTag(ctx context.Context, id string) (*gtsmodel.Tag, error) {
-	return m.state.Caches.GTS.Tag().Load("ID", func() (*gtsmodel.Tag, error) {
+func (t *tagDB) GetTag(ctx context.Context, id string) (*gtsmodel.Tag, error) {
+	return t.state.Caches.GTS.Tag.LoadOne("ID", func() (*gtsmodel.Tag, error) {
 		var tag gtsmodel.Tag
 
-		q := m.conn.
+		q := t.db.
 			NewSelect().
 			Model(&tag).
 			Where("? = ?", bun.Ident("tag.id"), id)
@@ -49,15 +49,15 @@ func (m *tagDB) GetTag(ctx context.Context, id string) (*gtsmodel.Tag, error) {
 	}, id)
 }
 
-func (m *tagDB) GetTagByName(ctx context.Context, name string) (*gtsmodel.Tag, error) {
+func (t *tagDB) GetTagByName(ctx context.Context, name string) (*gtsmodel.Tag, error) {
 	// Normalize 'name' string.
 	name = strings.TrimSpace(name)
 	name = strings.ToLower(name)
 
-	return m.state.Caches.GTS.Tag().Load("Name", func() (*gtsmodel.Tag, error) {
+	return t.state.Caches.GTS.Tag.LoadOne("Name", func() (*gtsmodel.Tag, error) {
 		var tag gtsmodel.Tag
 
-		q := m.conn.
+		q := t.db.
 			NewSelect().
 			Model(&tag).
 			Where("? = ?", bun.Ident("tag.name"), name)
@@ -70,25 +70,52 @@ func (m *tagDB) GetTagByName(ctx context.Context, name string) (*gtsmodel.Tag, e
 	}, name)
 }
 
-func (m *tagDB) GetTags(ctx context.Context, ids []string) ([]*gtsmodel.Tag, error) {
-	tags := make([]*gtsmodel.Tag, 0, len(ids))
-
-	for _, id := range ids {
-		// Attempt fetch from DB
-		tag, err := m.GetTag(ctx, id)
-		if err != nil {
-			log.Errorf(ctx, "error getting tag %q: %v", id, err)
-			continue
-		}
-
-		// Append tag
-		tags = append(tags, tag)
+func (t *tagDB) GetTags(ctx context.Context, ids []string) ([]*gtsmodel.Tag, error) {
+	// Preallocate at-worst possible length.
+	uncached := make([]string, 0, len(ids))
+
+	// Load all tag IDs via cache loader callbacks.
+	tags, err := t.state.Caches.GTS.Tag.Load("ID",
+
+		// Load cached + check for uncached.
+		func(load func(keyParts ...any) bool) {
+			for _, id := range ids {
+				if !load(id) {
+					uncached = append(uncached, id)
+				}
+			}
+		},
+
+		// Uncached tag loader function.
+		func() ([]*gtsmodel.Tag, error) {
+			// Preallocate expected length of uncached tags.
+			tags := make([]*gtsmodel.Tag, 0, len(uncached))
+
+			// Perform database query scanning
+			// the remaining (uncached) IDs.
+			if err := t.db.NewSelect().
+				Model(&tags).
+				Where("? IN (?)", bun.Ident("id"), bun.In(uncached)).
+				Scan(ctx); err != nil {
+				return nil, err
+			}
+
+			return tags, nil
+		},
+	)
+	if err != nil {
+		return nil, err
 	}
 
+	// Reorder the tags by their
+	// IDs to ensure in correct order.
+	getID := func(t *gtsmodel.Tag) string { return t.ID }
+	util.OrderBy(tags, ids, getID)
+
 	return tags, nil
 }
 
-func (m *tagDB) PutTag(ctx context.Context, tag *gtsmodel.Tag) error {
+func (t *tagDB) PutTag(ctx context.Context, tag *gtsmodel.Tag) error {
 	// Normalize 'name' string before it enters
 	// the db, without changing tag we were given.
 	//
@@ -101,8 +128,8 @@ func (m *tagDB) PutTag(ctx context.Context, tag *gtsmodel.Tag) error {
 	t2.Name = strings.ToLower(t2.Name)
 
 	// Insert the copy.
-	if err := m.state.Caches.GTS.Tag().Store(t2, func() error {
-		_, err := m.conn.NewInsert().Model(t2).Exec(ctx)
+	if err := t.state.Caches.GTS.Tag.Store(t2, func() error {
+		_, err := t.db.NewInsert().Model(t2).Exec(ctx)
 		return err
 	}); err != nil {
 		return err // err already processed