datastore: fix get query caching

This change replaces caching the DB pgx.Rows, which is an iterator, with
the actual potential vulnerabilities. Previously, subsequent records
manifesting in the same query were given a pgx.Rows object that had been
exhausted.

Signed-off-by: crozzy <joseph.crosland@gmail.com>

Author: crozzy

datastore/postgres/get.go

@@ -51,7 +51,7 @@ func (s *MatcherStore) Get(ctx context.Context, records []*claircore.IndexRecord
 	defer tx.Rollback(ctx)
 	// start a batch
 	batch := &pgx.Batch{}
-	resCache := map[string]pgx.Rows{}
+	resCache := map[string][]*claircore.Vulnerability{}
 	rqs := []*recordQuery{}
 	for _, record := range records {
 		query, err := buildGetQuery(record, &opts)
@@ -72,7 +72,6 @@ func (s *MatcherStore) Get(ctx context.Context, records []*claircore.IndexRecord
 		resCache[query] = nil
 	}
 	// send the batch
-
 	start := time.Now()
 	res := tx.SendBatch(ctx, batch)
 	// Can't just defer the close, because the batch must be fully handled
@@ -83,72 +82,89 @@ func (s *MatcherStore) Get(ctx context.Context, records []*claircore.IndexRecord
 	results := make(map[string][]*claircore.Vulnerability)
 	vulnSet := make(map[string]map[string]struct{})
 	for _, rq := range rqs {
-		rows, ok := resCache[rq.query]
+		rid := rq.record.Package.ID
+		vulns, ok := resCache[rq.query]
 		if !ok {
 			return nil, fmt.Errorf("unexpected vulnerability query: %s", rq.query)
 		}
-		if rows == nil {
-			rows, err = res.Query()
-			if err != nil {
-				res.Close()
-				return nil, err
+		if vulns != nil { // We already have results we don't need to go back to the DB.
+			if _, ok := vulnSet[rid]; !ok {
+				vulnSet[rid] = make(map[string]struct{})
 			}
-			resCache[rq.query] = rows
-		}
-
-		// unpack all returned rows into claircore.Vulnerability structs
-		for rows.Next() {
-			// fully allocate vuln struct
-			v := &claircore.Vulnerability{
-				Package: &claircore.Package{},
-				Dist:    &claircore.Distribution{},
-				Repo:    &claircore.Repository{},
+			for _, v := range vulns {
+				if _, ok := vulnSet[rid][v.ID]; !ok {
+					vulnSet[rid][v.ID] = struct{}{}
+					results[rid] = append(results[rid], v)
+				}
 			}
-
-			var id int64
-			err := rows.Scan(
-				&id,
-				&v.Name,
-				&v.Description,
-				&v.Issued,
-				&v.Links,
-				&v.Severity,
-				&v.NormalizedSeverity,
-				&v.Package.Name,
-				&v.Package.Version,
-				&v.Package.Module,
-				&v.Package.Arch,
-				&v.Package.Kind,
-				&v.Dist.DID,
-				&v.Dist.Name,
-				&v.Dist.Version,
-				&v.Dist.VersionCodeName,
-				&v.Dist.VersionID,
-				&v.Dist.Arch,
-				&v.Dist.CPE,
-				&v.Dist.PrettyName,
-				&v.ArchOperation,
-				&v.Repo.Name,
-				&v.Repo.Key,
-				&v.Repo.URI,
-				&v.FixedInVersion,
-				&v.Updater,
-			)
-			v.ID = strconv.FormatInt(id, 10)
+			continue
+		}
+		results[rid] = []*claircore.Vulnerability{}
+		err := func() error {
+			rows, err := res.Query()
 			if err != nil {
 				res.Close()
-				return nil, fmt.Errorf("failed to scan vulnerability: %v", err)
+				return fmt.Errorf("error getting rows: %w", err)
 			}
+			defer rows.Close()
+			// unpack all returned rows into claircore.Vulnerability structs
+			for rows.Next() {
+				// fully allocate vuln struct
+				v := &claircore.Vulnerability{
+					Package: &claircore.Package{},
+					Dist:    &claircore.Distribution{},
+					Repo:    &claircore.Repository{},
+				}
 
-			rid := rq.record.Package.ID
-			if _, ok := vulnSet[rid]; !ok {
-				vulnSet[rid] = make(map[string]struct{})
-			}
-			if _, ok := vulnSet[rid][v.ID]; !ok {
-				vulnSet[rid][v.ID] = struct{}{}
-				results[rid] = append(results[rid], v)
+				var id int64
+				err := rows.Scan(
+					&id,
+					&v.Name,
+					&v.Description,
+					&v.Issued,
+					&v.Links,
+					&v.Severity,
+					&v.NormalizedSeverity,
+					&v.Package.Name,
+					&v.Package.Version,
+					&v.Package.Module,
+					&v.Package.Arch,
+					&v.Package.Kind,
+					&v.Dist.DID,
+					&v.Dist.Name,
+					&v.Dist.Version,
+					&v.Dist.VersionCodeName,
+					&v.Dist.VersionID,
+					&v.Dist.Arch,
+					&v.Dist.CPE,
+					&v.Dist.PrettyName,
+					&v.ArchOperation,
+					&v.Repo.Name,
+					&v.Repo.Key,
+					&v.Repo.URI,
+					&v.FixedInVersion,
+					&v.Updater,
+				)
+				v.ID = strconv.FormatInt(id, 10)
+				if err != nil {
+					res.Close()
+					return fmt.Errorf("failed to scan vulnerability: %w", err)
+				}
+
+				if _, ok := vulnSet[rid]; !ok {
+					vulnSet[rid] = make(map[string]struct{})
+				}
+				if _, ok := vulnSet[rid][v.ID]; !ok {
+					vulnSet[rid][v.ID] = struct{}{}
+					results[rid] = append(results[rid], v)
+				}
 			}
+			return nil
+		}()
+		if err != nil {
+			return nil, err
 		}
+		resCache[rq.query] = results[rid]
 	}
 	if err := res.Close(); err != nil {
 		return nil, fmt.Errorf("some weird batch error: %v", err)