prune active set from ballot blob (#5032)

## Motivation
Closes #4985

## Changes
- actually prune active set from ballot blobs in db
- use a empty migration to facilitate the pruning. 
  we only want to prune/vacuum/checkpoint once per software upgrade
  the code allow any upgrade from migration <=4 to 5 to
  - extract active set from ballots
  - prune active set from blob
  - vacuum and checkpoint

the final size of the state should be < 1GB

CHANGELOG.md

@@ -34,6 +34,7 @@ In order to enable provide following configuration:
   Ephemeral data are deleted and state compacted at the time of upgrade. In steady-state, data is pruned periodically.
 * [#5021](https://github.com/spacemeshos/go-spacemesh/pull/5021) Drop support for old certificate sync protocol.
 * [#5024](https://github.com/spacemeshos/go-spacemesh/pull/5024) Active set will be saved in state separately from ballots.
+* [#5032](https://github.com/spacemeshos/go-spacemesh/pull/5032) Ativeset data pruned from ballots.
 * [#5035](https://github.com/spacemeshos/go-spacemesh/pull/5035) Fix possible nil pointer panic when node fails to persist nipost builder state.
 
 ## v1.1.5

sql/ballots/util/extract.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/spacemeshos/go-spacemesh/codec"
 	"github.com/spacemeshos/go-spacemesh/common/types"
 	"github.com/spacemeshos/go-spacemesh/log"
 	"github.com/spacemeshos/go-spacemesh/sql"
@@ -42,11 +43,10 @@ func ExtractActiveSet(db sql.Executor) error {
 			} else if err == nil {
 				unique++
 			}
-			// TODO: prune ballot active set after migration 4 is released
-			//b.ActiveSet = nil
-			//if err := ballots.UpdateBlob(db, b.ID(), codec.MustEncode(b)); err != nil {
-			//	return fmt.Errorf("update ballot %s: %w", b.ID().String(), err)
-			//}
+			b.ActiveSet = nil
+			if err := ballots.UpdateBlob(db, b.ID(), codec.MustEncode(b)); err != nil {
+				return fmt.Errorf("update ballot %s: %w", b.ID().String(), err)
+			}
 			extracted++
 		}
 	}

sql/ballots/util/extract_test.go

@@ -45,9 +45,7 @@ func TestExtractActiveSet(t *testing.T) {
 	for _, b := range blts {
 		got, err := ballots.Get(db, b.ID())
 		require.NoError(t, err)
-		if b.Layer%3 != 2 {
-			require.NotEmpty(t, got.ActiveSet)
-		}
+		require.Nil(t, got.ActiveSet)
 	}
 	for i, h := range hashes {
 		got, err := activesets.Get(db, h)

sql/database.go

@@ -141,12 +141,8 @@ func Open(uri string, opts ...Opt) (*Database, error) {
 		if err != nil {
 			return nil, err
 		}
-		after, err := version(db)
-		if err != nil {
-			return nil, err
-		}
-		if before <= 4 && after == 5 && config.v5Migration != nil {
-			// v5 migration (active set extraction) needs the 4rd migration to execute first
+		if before <= 4 && config.v5Migration != nil {
+			// v5 migration (active set extraction) needs the 3rd migration to execute first
 			if err := config.v5Migration(db); err != nil {
 				return nil, err
 			}

sql/migrations/0004_v1.1.7.sql

@@ -1 +1 @@
-CREATE INDEX ballots_by_atx_by_layer ON ballots (atx, layer asc);
+CREATE INDEX ballots_by_atx_by_layer ON ballots (atx, layer asc);

sql/migrations/0005_next.sql

@@ -1,3 +1,3 @@
 DELETE FROM proposals;
 DELETE FROM proposal_transactions;
-UPDATE certificates SET cert = NULL WHERE layer < 19000;
+UPDATE certificates SET cert = NULL WHERE layer < 20000;