Add ListCollection for meta table

Signed-off-by: Nneza2017 <yefu.chen@zilliz.com>

docs/developer_guides/developer_guides.md

@@ -1133,6 +1133,7 @@ func (meta *metaTable) AddCollection(coll *CollectionMeta) error
 func (meta *metaTable) DeleteCollection(collId UniqueId) error
 func (meta *metaTable) HasCollection(collId UniqueId) bool
 func (meta *metaTable) GetCollectionByName(collName string) (*CollectionMeta, error)
+func (meta *metaTable) ListCollections()([]string, error)
 
 func (meta *metaTable) AddPartition(collId UniqueId, tag string) error
 func (meta *metaTable) HasPartition(collId UniqueId, tag string) bool

internal/master/meta_table.go

@@ -287,6 +287,17 @@ func (mt *metaTable) GetCollectionByName(collectionName string) (*pb.CollectionM
 	return &col, nil
 }
 
+func (mt *metaTable) ListCollections() ([]string, error) {
+	mt.ddLock.RLock()
+	defer mt.ddLock.RUnlock()
+
+	colls := make([]string, 0, len(mt.collName2ID))
+	for name := range mt.collName2ID {
+		colls = append(colls, name)
+	}
+	return colls, nil
+}
+
 func (mt *metaTable) AddPartition(collID UniqueID, tag string) error {
 	mt.ddLock.Lock()
 	defer mt.ddLock.Unlock()

internal/master/meta_table_test.go

@@ -102,6 +102,11 @@ func TestMetaTable_Collection(t *testing.T) {
 	assert.NotNil(t, err)
 	err = meta.AddCollection(&colMeta5)
 	assert.NotNil(t, err)
+
+	collsName, err := meta.ListCollections()
+	assert.Nil(t, err)
+	assert.Equal(t, collsName, []string{"coll1", "coll2"})
+
 	hasCollection := meta.HasCollection(colMeta.ID)
 	assert.True(t, hasCollection)
 	err = meta.AddPartition(colMeta.ID, "p1")