allow ingest API delete to work at all, add test for it

The ingest API tried to do a Qcx operation that needs a write Tx after
requesting a write Tx. This doesn't work. The ingest API is the only caller
of clearExistenceColumns, so it's easy to just make it work for a given
shard using a provided Tx. This isn't especially clean, but a lot of this
is due for an overhaul anyway because the Qcx/Tx stuff is sort of broken.

Also, add any test case at all for this, since we didn't have one, and
also fix the fact that the test case failed because the test harness
didn't allow empty result sets.

api.go

@@ -1919,7 +1919,7 @@ func (api *API) applyOperations(ctx context.Context, qcx *Qcx, index *Index, sha
 				// We delete from the existence field unconditionally and other fields
 				// if we know they exist.
 				if op.OpType == ingest.OpDelete {
-					err = clearExistenceColumns(qcx, index, op.ClearRecordIDs, shard)
+					err = clearExistenceColumns(tx, index, op.ClearRecordIDs, shard)
 					if err != nil {
 						return fmt.Errorf("clearing existence columns: %w", err)
 					}
@@ -1997,21 +1997,20 @@ func importExistenceColumns(qcx *Qcx, index *Index, columnIDs []uint64, shard ui
 	return ef.Import(qcx, existenceRowIDs, columnCopy, nil, shard, &options)
 }
 
-func clearExistenceColumns(qcx *Qcx, index *Index, columnIDs []uint64, shard uint64) error {
+func clearExistenceColumns(tx Tx, index *Index, columnIDs []uint64, shard uint64) error {
 	ef := index.existenceField()
 	if ef == nil {
 		return nil
 	}
-
-	existenceRowIDs := make([]uint64, len(columnIDs))
-	// If we don't gratuitously hand-duplicate things in field.Import,
-	// the fact that fragment.bulkImport rewrites its row and column
-	// lists can burn us if we don't make a copy before doing the
-	// existence field write.
-	columnCopy := make([]uint64, len(columnIDs))
-	copy(columnCopy, columnIDs)
-	options := ImportOptions{Clear: true}
-	return ef.Import(qcx, existenceRowIDs, columnCopy, nil, shard, &options)
+	v := ef.view("standard")
+	if v == nil {
+		return nil
+	}
+	f := v.Fragment(shard)
+	if f == nil {
+		return nil
+	}
+	return f.ClearRecords(tx, columnIDs)
 }
 
 // ShardDistribution returns an object representing the distribution of shards

ingest_test.go

@@ -146,6 +146,9 @@ func parseExpectedResults(data []byte) (ints []uint64, keys []string, err error)
 		return nil, nil, errors.New("expecting [] results")
 	}
 	words := bytes.Split(data[1:len(data)-1], []byte{','})
+	if len(words) == 1 && len(words[0]) == 0 {
+		return nil, nil, nil
+	}
 	for _, word := range words {
 		word = bytes.TrimSpace(word)
 		if len(word) == 0 {

ingest_testdata/sample.tc

@@ -87,3 +87,13 @@ ingest-error:
     }
   }
 ]
+ingest:
+[
+  {
+    "action": "delete",
+    "record_ids": [ 1 ]
+  }
+]
+queries:
+Row(setkey="a")
+[]