From 4c1b0497dfc1bb8050b3d0766322289225364a54 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Thu, 18 Apr 2024 20:32:58 -0300
Subject: [PATCH] lmdb/badger/bolt: actually stop the cursor when we have
 pulled enough.

---
 badger/query.go | 16 ++++++++++++----
 bolt/query.go   |  9 +++++----
 lmdb/query.go   | 13 ++++++-------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/badger/query.go b/badger/query.go
index eaf2e74..de1a9e0 100644
--- a/badger/query.go
+++ b/badger/query.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/binary"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"log"
 
@@ -26,6 +27,8 @@ type queryEvent struct {
 	query int
 }
 
+var exit = errors.New("exit")
+
 func (b BadgerBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (chan *nostr.Event, error) {
 	ch := make(chan *nostr.Event)
 
@@ -87,7 +90,8 @@ func (b BadgerBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (ch
 							idx, q.prefix, key, err)
 						return err
 					}
-					item.Value(func(val []byte) error {
+
+					if err := item.Value(func(val []byte) error {
 						evt := &nostr.Event{}
 						if err := nostr_binary.Unmarshal(val, evt); err != nil {
 							log.Printf("badger: value read error (id %x): %s\n", val[0:32], err)
@@ -100,15 +104,19 @@ func (b BadgerBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (ch
 							case q.results <- evt:
 								pulled++
 								if pulled > limit {
-									break
+									return exit
 								}
 							case <-ctx.Done():
-								break
+								return exit
 							}
 						}
 
 						return nil
-					})
+					}); err == exit {
+						return nil
+					} else if err != nil {
+						return err
+					}
 				}
 
 				return nil
diff --git a/bolt/query.go b/bolt/query.go
index dc657ca..16937d4 100644
--- a/bolt/query.go
+++ b/bolt/query.go
@@ -69,7 +69,7 @@ func (b *BoltBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 					if !q.skipTimestamp {
 						createdAt := binary.BigEndian.Uint32(k[len(k)-4:])
 						if createdAt < since {
-							break
+							return nil
 						}
 					}
 
@@ -78,7 +78,7 @@ func (b *BoltBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 					evt := &nostr.Event{}
 					if err := nostr_binary.Unmarshal(val, evt); err != nil {
 						log.Printf("bolt: value read error (id %x): %s\n", val[0:32], err)
-						break
+						return fmt.Errorf("error: %w", err)
 					}
 
 					// check if this matches the other filters that were not part of the index before yielding
@@ -87,13 +87,14 @@ func (b *BoltBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 						case q.results <- evt:
 							pulled++
 							if pulled > limit {
-								break
+								return nil
 							}
 						case <-ctx.Done():
-							break
+							return nil
 						}
 					}
 				}
+
 				return nil
 			})
 		}
diff --git a/lmdb/query.go b/lmdb/query.go
index aacd3f3..aabf222 100644
--- a/lmdb/query.go
+++ b/lmdb/query.go
@@ -84,14 +84,14 @@ func (b *LMDBBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 						len(k) != q.prefixSize+q.timestampSize ||
 						!bytes.Equal(k[:q.prefixSize], q.prefix) {
 						// either iteration has errored or we reached the end of this prefix
-						break // stop this cursor and move to the next one
+						return nil
 					}
 
 					// "id" indexes don't contain a timestamp
 					if q.timestampSize == 4 {
 						createdAt := binary.BigEndian.Uint32(k[len(k)-4:])
 						if createdAt < since {
-							break
+							return nil
 						}
 					}
 
@@ -101,13 +101,13 @@ func (b *LMDBBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 						log.Printf(
 							"lmdb: failed to get %x based on prefix %x, index key %x from raw event store: %s\n",
 							idx, q.prefix, k, err)
-						break
+						return fmt.Errorf("error: %w", err)
 					}
 
 					evt := &nostr.Event{}
 					if err := nostr_binary.Unmarshal(val, evt); err != nil {
 						log.Printf("lmdb: value read error (id %x): %s\n", val[0:32], err)
-						break
+						return fmt.Errorf("error: %w", err)
 					}
 
 					// check if this matches the other filters that were not part of the index before yielding
@@ -116,17 +116,16 @@ func (b *LMDBBackend) QueryEvents(ctx context.Context, filter nostr.Filter) (cha
 						case q.results <- evt:
 							pulled++
 							if pulled >= limit {
-								break
+								return nil
 							}
 						case <-ctx.Done():
-							break
+							return nil
 						}
 					}
 
 					// move one back (we'll look into k and v and err in the next iteration)
 					k, idx, iterr = cursor.Get(nil, nil, lmdb.Prev)
 				}
-				return nil
 			})
 		}
 		if err != nil {