search optimisation

internal/api/search_index.go

@@ -0,0 +1,110 @@
+package api
+
+import (
+	"log"
+	"net/http"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/metazla/meta-core/internal/storage"
+)
+
+// searchIndexRefreshInterval is how often the in-memory search index is rebuilt
+// from Redis in the background. Records ingest continuously, so a newly stored
+// record becomes searchable within one interval; the rebuild is a single
+// batched bulk read (storage.GetSearchIndexTuples), off the request path.
+const searchIndexRefreshInterval = 60 * time.Second
+
+// searchIndex is an in-memory snapshot of every record's search haystack
+// (hashID + lowercased searchable fields), rebuilt periodically from Redis. It
+// exists so POST /api/metadata/search matches in memory (string ops over a
+// slice) instead of doing a SCAN+MGET Redis round-trip per record — the latter
+// took 40s+ over ~72k records and made a live parallel search path unusable.
+type searchIndex struct {
+	mu     sync.RWMutex
+	tuples []storage.SearchTuple
+	ready  atomic.Bool
+}
+
+// snapshot returns the current tuples slice and whether the index has built at
+// least once. The refresh swaps in a fresh slice under the write lock (never
+// mutates in place), so the returned slice is safe to read lock-free.
+func (idx *searchIndex) snapshot() ([]storage.SearchTuple, bool) {
+	idx.mu.RLock()
+	defer idx.mu.RUnlock()
+	return idx.tuples, idx.ready.Load()
+}
+
+// refresh rebuilds the index from Redis once (a batched bulk read).
+func (idx *searchIndex) refresh(stor *storage.Client) {
+	if stor == nil || !stor.IsConnected() {
+		return
+	}
+	tuples, err := stor.GetSearchIndexTuples()
+	if err != nil {
+		log.Printf("[API] search index refresh failed: %v", err)
+		return
+	}
+	idx.mu.Lock()
+	idx.tuples = tuples
+	idx.mu.Unlock()
+	idx.ready.Store(true)
+}
+
+// runRefreshLoop builds the index immediately, then rebuilds on a ticker for the
+// process lifetime.
+func (idx *searchIndex) runRefreshLoop(stor *storage.Client) {
+	idx.refresh(stor)
+	ticker := time.NewTicker(searchIndexRefreshInterval)
+	defer ticker.Stop()
+	for range ticker.C {
+		idx.refresh(stor)
+	}
+}
+
+// serveIndexedSearch answers a free-text (non-property) query from the in-memory
+// index: token-AND match against each record's haystack (or a whole-query hashID
+// substring, preserving the legacy behaviour), then fetch full metadata for only
+// the <=limit matches. No Redis round-trip per scanned record.
+func (s *Server) serveIndexedSearch(w http.ResponseWriter, req MetadataSearchRequest) {
+	tuples, ready := s.search.snapshot()
+	if !ready {
+		// First call before the background build finished: warm inline with the
+		// efficient batched read (seconds), never the per-record SCAN fallback.
+		s.search.refresh(s.storage)
+		tuples, _ = s.search.snapshot()
+	}
+	tokens := strings.Fields(strings.ToLower(req.Query))
+	queryLower := strings.ToLower(req.Query)
+	results := make([]MetadataSearchResult, 0, req.Limit)
+	for _, t := range tuples {
+		if len(results) >= req.Limit {
+			break
+		}
+		if !matchAllTokens(t.Haystack, tokens) &&
+			!strings.Contains(strings.ToLower(t.HashID), queryLower) {
+			continue
+		}
+		// Full metadata is cached in the index — return it straight from memory,
+		// no Redis round-trip per result.
+		results = append(results, MetadataSearchResult{HashID: t.HashID, Metadata: t.Fields})
+	}
+	writeJSON(w, http.StatusOK, MetadataSearchResponse{
+		Results: results,
+		Count:   len(results),
+		Total:   len(tuples),
+	})
+}
+
+// matchAllTokens reports whether haystack contains every token (AND semantics).
+// An empty token list matches everything.
+func matchAllTokens(haystack string, tokens []string) bool {
+	for _, t := range tokens {
+		if !strings.Contains(haystack, t) {
+			return false
+		}
+	}
+	return true
+}