[chore/performance] Batch migration queries (#3798)

* separate enum migrations into their own individual transactions

* pee poo

* some performance tweaks and adding more comments

* batch

---------

Co-authored-by: kim <grufwub@gmail.com>

internal/db/bundb/migrations/20241121121623_enum_strings_to_ints.go

@@ -30,8 +30,6 @@
 
 func init() {
 	up := func(ctx context.Context, db *bun.DB) error {
-		return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
-
 		// Status visibility type indices.
 		var statusVisIndices = []struct {
 			name  string
@@ -61,6 +59,7 @@ func init() {
 			Column               string
 			Default              *new_gtsmodel.Visibility
 			IndexCleanupCallback func(ctx context.Context, tx bun.Tx) error
+			BatchByColumn        string
 		}{
 			{
 				Table:  "statuses",
@@ -78,19 +77,26 @@ func init() {
 					}
 					return nil
 				},
+				BatchByColumn: "id",
 			},
 			{
 				Table:         "sin_bin_statuses",
 				Column:        "visibility",
+				BatchByColumn: "id",
 			},
 			{
 				Table:         "account_settings",
 				Column:        "privacy",
-					Default: util.Ptr(new_gtsmodel.VisibilityDefault)},
+				Default:       util.Ptr(new_gtsmodel.VisibilityDefault),
+				BatchByColumn: "account_id",
+			},
+
 			{
 				Table:         "account_settings",
 				Column:        "web_visibility",
-					Default: util.Ptr(new_gtsmodel.VisibilityDefault)},
+				Default:       util.Ptr(new_gtsmodel.VisibilityDefault),
+				BatchByColumn: "account_id",
+			},
 		}
 
 		// Get the mapping of old enum string values to new integer values.
@@ -98,8 +104,12 @@ func init() {
 
 		// Convert all visibility tables.
 		for _, table := range visTables {
-				if err := convertEnums(ctx, tx, table.Table, table.Column,
-					visibilityMapping, table.Default, table.IndexCleanupCallback); err != nil {
+
+			// Perform each enum table conversion within its own transaction.
+			if err := db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+				return convertEnums(ctx, tx, table.Table, table.Column,
+					visibilityMapping, table.Default, table.IndexCleanupCallback, table.BatchByColumn)
+			}); err != nil {
 				return err
 			}
 		}
@@ -108,7 +118,7 @@ func init() {
 		log.Info(ctx, "creating new visibility indexes...")
 		for _, index := range statusVisIndices {
 			log.Infof(ctx, "creating new index %s...", index.name)
-				q := tx.NewCreateIndex().
+			q := db.NewCreateIndex().
 				Table("statuses").
 				Index(index.name).
 				Column(index.cols...)
@@ -123,14 +133,15 @@ func init() {
 		// Get the mapping of old enum string values to the new integer value types.
 		notificationMapping := notificationEnumMapping[old_gtsmodel.NotificationType]()
 
-			// Migrate over old notifications table column over to new column type.
-			if err := convertEnums(ctx, tx, "notifications", "notification_type", //nolint:revive
-				notificationMapping, nil, nil); err != nil {
+		// Migrate over old notifications table column to new type in tx.
+		if err := db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+			return convertEnums(ctx, tx, "notifications", "notification_type", //nolint:revive
+				notificationMapping, nil, nil, "id")
+		}); err != nil {
 			return err
 		}
 
 		return nil
-		})
 	}
 
 	down := func(ctx context.Context, db *bun.DB) error {

internal/db/bundb/migrations/util.go

@@ -22,11 +22,13 @@
 	"errors"
 	"fmt"
 	"reflect"
+	"slices"
 	"strconv"
 	"strings"
 
 	"codeberg.org/gruf/go-byteutil"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/id"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/uptrace/bun"
 	"github.com/uptrace/bun/dialect"
@@ -46,6 +48,7 @@ func convertEnums[OldType ~string, NewType ~int16](
 	mapping map[OldType]NewType,
 	defaultValue *NewType,
 	indexCleanupCallback func(context.Context, bun.Tx) error,
+	batchByColumn string,
 ) error {
 	if len(mapping) == 0 {
 		return errors.New("empty mapping")
@@ -87,7 +90,7 @@ func convertEnums[OldType ~string, NewType ~int16](
 	var qbuf byteutil.Buffer
 
 	// Prepare a singular UPDATE statement using
-	// SET $newColumn = (CASE $column WHEN $old THEN $new ... END)
+	// SET $newColumn = (CASE $column WHEN $old THEN $new ... END).
 	qbuf.B = append(qbuf.B, "UPDATE ? SET ? = (CASE ? "...)
 	args = append(args, bun.Ident(table))
 	args = append(args, bun.Ident(newColumn))
@@ -99,16 +102,82 @@ func convertEnums[OldType ~string, NewType ~int16](
 	qbuf.B = append(qbuf.B, "ELSE ? END)"...)
 	args = append(args, *defaultValue)
 
+	// Serialize it here to be
+	// used as the base for each
+	// set of batch queries below.
+	baseQStr := string(qbuf.B)
+	baseArgs := args
+
+	// Query batch size
+	// in number of rows.
+	const batchsz = 5000
+
+	// Stores highest batch value
+	// used in iterate queries,
+	// starting at highest possible.
+	highest := id.Highest
+
+	// Total updated rows.
+	var updated int
+
+	for {
+		// Limit to batchsz
+		// items at once.
+		batchQ := tx.
+			NewSelect().
+			Table(table).
+			Column(batchByColumn).
+			Where("? < ?", bun.Ident(batchByColumn), highest).
+			OrderExpr("? DESC", bun.Ident(batchByColumn)).
+			Limit(batchsz)
+
+		// Finalize UPDATE to operate on this batch only.
+		qStr := baseQStr + " WHERE ? IN (?)"
+		args := append(
+			slices.Clone(baseArgs),
+			bun.Ident(batchByColumn),
+			batchQ,
+		)
+
 		// Execute the prepared raw query with arguments.
-	res, err := tx.NewRaw(qbuf.String(), args...).Exec(ctx)
+		res, err := tx.NewRaw(qStr, args...).Exec(ctx)
 		if err != nil {
 			return gtserror.Newf("error updating old column values: %w", err)
 		}
 
-	// Count number items updated.
-	updated, _ := res.RowsAffected()
+		// Check how many items we updated.
+		thisUpdated, err := res.RowsAffected()
+		if err != nil {
+			return gtserror.Newf("error counting affected rows: %w", err)
+		}
+
+		if thisUpdated == 0 {
+			// Nothing updated
+			// means we're done.
+			break
+		}
+
+		// Update the overall count.
+		updated += int(thisUpdated)
+
+		// Log helpful message to admin.
+		log.Infof(ctx, "migrated %d of %d %s (up to %s)",
+			updated, total, table, highest)
+
+		// Get next highest
+		// id for next batch.
+		if err := tx.
+			NewSelect().
+			With("batch_query", batchQ).
+			ColumnExpr("min(?) FROM ?", bun.Ident(batchByColumn), bun.Ident("batch_query")).
+			Scan(ctx, &highest); err != nil {
+			return gtserror.Newf("error selecting next highest: %w", err)
+		}
+	}
+
 	if total != int(updated) {
-		log.Warnf(ctx, "total=%d does not match updated=%d", total, updated)
+		// Return error here in order to rollback the whole transaction.
+		return fmt.Errorf("total=%d does not match updated=%d", total, updated)
 	}
 
 	// Run index cleanup callback if set.