vochain/indexer: use prepared statements for queries

Allows sqlite to reuse some of the work when parsing each query.

              │     old     │                new                │
              │   sec/op    │   sec/op     vs base              │
    Indexer-8   54.39m ± 0%   53.73m ± 0%  -1.21% (p=0.001 n=7)

              │     old      │                new                 │
              │     B/op     │     B/op      vs base              │
    Indexer-8   874.1Ki ± 0%   842.1Ki ± 0%  -3.66% (p=0.001 n=7)

              │     old     │                new                │
              │  allocs/op  │  allocs/op   vs base              │
    Indexer-8   23.92k ± 0%   22.73k ± 0%  -4.98% (p=0.001 n=7)

vochain/indexer/indexer.go

@@ -77,7 +77,8 @@ type Indexer struct {
 	// blockTx is an in-progress SQL transaction which is committed or rolled
 	// back along with the current block.
 	blockTx *sql.Tx
-	// blockQueries wraps blockTx.
+	// blockQueries wraps blockTx. Note that it is kept between multiple transactions
+	// so that we can reuse the same prepared statements.
 	blockQueries *indexerdb.Queries
 	// blockUpdateProcs is the list of process IDs that require sync with the state database.
 	// The key is a types.ProcessID as a string, so that it can be used as a map key.
@@ -150,7 +151,14 @@ func NewIndexer(dataDir string, app *vochain.BaseApplication, countLiveResults b
 		return nil, fmt.Errorf("goose up: %w", err)
 	}
 
-	idx.readOnlyQuery = indexerdb.New(idx.readOnlyDB)
+	idx.readOnlyQuery, err = indexerdb.Prepare(context.TODO(), idx.readOnlyDB)
+	if err != nil {
+		return nil, err
+	}
+	idx.blockQueries, err = indexerdb.Prepare(context.TODO(), idx.readWriteDB)
+	if err != nil {
+		panic(err)
+	}
 
 	// Subscribe to events
 	idx.App.State.AddEventListener(idx)
@@ -179,7 +187,7 @@ func (idx *Indexer) blockTxQueries() *indexerdb.Queries {
 			panic(err) // shouldn't happen, use an error return if it ever does
 		}
 		idx.blockTx = tx
-		idx.blockQueries = indexerdb.New(idx.blockTx)
+		idx.blockQueries = idx.blockQueries.WithTx(tx)
 	}
 	return idx.blockQueries
 }
@@ -292,7 +300,6 @@ func (idx *Indexer) AfterSyncBootstrap(inTest bool) {
 		log.Errorw(err, "could not commit tx")
 	}
 	idx.blockTx = nil
-	idx.blockQueries = nil
 
 	log.Infof("live results recovery computation finished, took %s", time.Since(startTime))
 }
@@ -402,7 +409,6 @@ func (idx *Indexer) Commit(height uint32) error {
 		log.Errorw(err, "could not commit tx")
 	}
 	idx.blockTx = nil
-	idx.blockQueries = nil
 
 	if newVotes+overwritedVotes > 0 {
 		log.Infow("add live votes to results",
@@ -423,7 +429,6 @@ func (idx *Indexer) Rollback() {
 			log.Errorw(err, "could not rollback tx")
 		}
 		idx.blockTx = nil
-		idx.blockQueries = nil
 	}
 	maps.Clear(idx.blockUpdateProcs)
 }

vochain/indexer/sqlc.yaml

@@ -7,6 +7,7 @@ sql:
     go:
       package: "indexerdb"
       out: "db"
+      emit_prepared_queries: true
       overrides:
       # Defaults to int32 for integers, which is a bit small.
       - db_type: "int"