fix: Ensure tags are never null

influxdb3/tests/server/query.rs

@@ -1330,3 +1330,49 @@ async fn api_v3_query_sql_meta_cache() {
         resp
     );
 }
+
+/// Test that if we write in a row of LP that is missing a tag value, we're still able to query.
+#[tokio::test]
+async fn api_v3_query_null_tag_values() {
+    let server = TestServer::spawn().await;
+
+    server
+        .write_lp_to_db(
+            "foo",
+            "cpu,host=a,region=us-east usage=0.9 1
+            cpu,host=b usage=0.80 4",
+            Precision::Second,
+        )
+        .await
+        .unwrap();
+
+    let client = reqwest::Client::new();
+    let url = format!("{base}/api/v3/query_sql", base = server.client_addr());
+
+    let resp = client
+        .get(&url)
+        .query(&[
+            ("db", "foo"),
+            (
+                "q",
+                "SELECT host, region, time, usage FROM cpu ORDER BY time",
+            ),
+            ("format", "pretty"),
+        ])
+        .send()
+        .await
+        .unwrap()
+        .text()
+        .await
+        .unwrap();
+
+    assert_eq!(
+        "+------+---------+---------------------+-------+\n\
+            | host | region  | time                | usage |\n\
+            +------+---------+---------------------+-------+\n\
+            | a    | us-east | 1970-01-01T00:00:01 | 0.9   |\n\
+            | b    |         | 1970-01-01T00:00:04 | 0.8   |\n\
+            +------+---------+---------------------+-------+",
+        resp
+    );
+}

influxdb3_write/src/write_buffer/table_buffer.rs

@@ -282,7 +282,7 @@ impl MutableTableChunk {
                             let mut tag_builder = StringDictionaryBuilder::new();
                             // append nulls for all previous rows
                             for _ in 0..(row_index + self.row_count) {
-                                tag_builder.append_null();
+                                tag_builder.append_value("");
                             }
                             e.insert(Builder::Tag(tag_builder));
                         }
@@ -390,8 +390,8 @@ impl MutableTableChunk {
                         Builder::I64(b) => b.append_null(),
                         Builder::U64(b) => b.append_null(),
                         Builder::String(b) => b.append_null(),
-                        Builder::Tag(b) => b.append_null(),
-                        Builder::Key(b) => b.append_null(),
+                        Builder::Tag(b) => b.append_value(""),
+                        Builder::Key(b) => b.append_value(""),
                         Builder::Time(b) => b.append_null(),
                     }
                 }
@@ -467,7 +467,10 @@ impl MutableTableChunk {
                 schema_builder.influx_column(col_name.as_ref(), InfluxColumnType::Tag);
                 let mut tag_builder: StringDictionaryBuilder<Int32Type> =
                     StringDictionaryBuilder::new();
-                tag_builder.append_nulls(self.row_count);
+                for _ in 0..self.row_count {
+                    tag_builder.append_value("");
+                }
+
                 cols.push(Arc::new(tag_builder.finish()));
             }
         }