fix: Set Slice start to Len if out-of-bound (#751)

Fix slice may panic with out of bound error when last batch is not
sufficent for batch size in query iterator

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

entity/columns_array.go

@@ -30,6 +30,9 @@ func (c *ColumnVarCharArray) Len() int {
 }
 
 func (c *ColumnVarCharArray) Slice(start, end int) Column {
+	if start > c.Len() {
+		start = c.Len()
+	}
 	if end == -1 || end > c.Len() {
 		end = c.Len()
 	}

entity/columns_json.go

@@ -36,6 +36,9 @@ func (c *ColumnJSONBytes) Len() int {
 }
 
 func (c *ColumnJSONBytes) Slice(start, end int) Column {
+	if start > c.Len() {
+		start = c.Len()
+	}
 	if end == -1 || end > c.Len() {
 		end = c.Len()
 	}

entity/columns_sparse.go

@@ -144,6 +144,9 @@ func (c *ColumnSparseFloatVector) Len() int {
 }
 
 func (c *ColumnSparseFloatVector) Slice(start, end int) Column {
+	if start > c.Len() {
+		start = c.Len()
+	}
 	if end == -1 || end > c.Len() {
 		end = c.Len()
 	}

entity/columns_varchar.go

@@ -46,6 +46,9 @@ func (c *ColumnVarChar) GetAsString(idx int) (string, error) {
 }
 
 func (c *ColumnVarChar) Slice(start, end int) Column {
+	if start > c.Len() {
+		start = c.Len()
+	}
 	if end == -1 || end > c.Len() {
 		end = c.Len()
 	}