Allow GROUP BY queries by providing deserialize_next_tagged to deserialize the group fields

influxdb/src/integrations/serde_integration/de.rs

@@ -1,4 +1,4 @@
-use super::Series;
+use super::{Series, TaggedSeries};
 use serde::de::{
     value, DeserializeSeed, Deserializer, Error, IntoDeserializer, MapAccess, SeqAccess, Visitor,
 };
@@ -96,6 +96,109 @@ where
     }
 }
 
+// Based on https://serde.rs/deserialize-struct.html
+impl<'de, TAG, T> Deserialize<'de> for TaggedSeries<TAG, T>
+where
+    TAG: Deserialize<'de>,
+    T: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        // Field name deserializer
+        #[derive(Deserialize)]
+        #[serde(field_identifier, rename_all = "lowercase")]
+        enum Field {
+            Name,
+            Tags,
+            Columns,
+            Values,
+        };
+
+        struct SeriesVisitor<TAG, T> {
+            _tag_type: PhantomData<TAG>,
+            _value_type: PhantomData<T>,
+        };
+
+        impl<'de, TAG, T> Visitor<'de> for SeriesVisitor<TAG, T>
+        where
+            TAG: Deserialize<'de>,
+            T: Deserialize<'de>,
+        {
+            type Value = TaggedSeries<TAG, T>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("struct TaggedSeries")
+            }
+
+            fn visit_map<V>(self, mut map: V) -> Result<TaggedSeries<TAG, T>, V::Error>
+            where
+                V: MapAccess<'de>,
+            {
+                let mut name = None;
+                let mut tags: Option<TAG> = None;
+                let mut columns: Option<Vec<String>> = None;
+                let mut values: Option<Vec<T>> = None;
+                while let Some(key) = map.next_key()? {
+                    match key {
+                        Field::Name => {
+                            if name.is_some() {
+                                return Err(Error::duplicate_field("name"));
+                            }
+                            name = Some(map.next_value()?);
+                        }
+                        Field::Tags => {
+                            if tags.is_some() {
+                                return Err(Error::duplicate_field("tags"));
+                            }
+                            tags = Some(map.next_value()?);
+                        }
+                        Field::Columns => {
+                            if columns.is_some() {
+                                return Err(Error::duplicate_field("columns"));
+                            }
+                            columns = Some(map.next_value()?);
+                        }
+                        Field::Values => {
+                            if values.is_some() {
+                                return Err(Error::duplicate_field("values"));
+                            }
+                            // Error out if "values" is encountered before "columns"
+                            // Hopefully, InfluxDB never does this.
+                            if columns.is_none() {
+                                return Err(Error::custom(
+                                    "series values encountered before columns",
+                                ));
+                            }
+                            // Deserialize using a HeaderVec deserializer
+                            // seeded with the headers from the "columns" field
+                            values = Some(map.next_value_seed(HeaderVec::<T> {
+                                header: columns.as_ref().unwrap(),
+                                _inner_type: PhantomData,
+                            })?);
+                        }
+                    }
+                }
+                let name = name.ok_or_else(|| Error::missing_field("name"))?;
+                let tags = tags.ok_or_else(|| Error::missing_field("tags"))?;
+                let values = values.ok_or_else(|| Error::missing_field("values"))?;
+                Ok(TaggedSeries { name, tags, values })
+            }
+        }
+
+        const FIELDS: &[&str] = &["name", "tags", "values"];
+        deserializer.deserialize_struct(
+            "TaggedSeries",
+            FIELDS,
+            SeriesVisitor::<TAG, T> {
+                _tag_type: PhantomData,
+                _value_type: PhantomData,
+            },
+        )
+    }
+}
+
 // Deserializer that takes a header as a seed
 // and deserializes an array of arrays into a
 // Vec of map-like values using the header as

influxdb/src/integrations/serde_integration/mod.rs

@@ -77,6 +77,20 @@ impl DatabaseQueryResult {
             }
         })
     }
+
+    pub fn deserialize_next_tagged<TAG, T: 'static>(
+        &mut self,
+    ) -> Result<TaggedReturn<TAG, T>, Error>
+    where
+        TAG: DeserializeOwned + Send,
+        T: DeserializeOwned + Send,
+    {
+        serde_json::from_value::<TaggedReturn<TAG, T>>(self.results.remove(0)).map_err(|err| {
+            Error::DeserializationError {
+                error: format!("could not deserialize: {}", err),
+            }
+        })
+    }
 }
 
 #[derive(Deserialize, Debug)]
@@ -93,6 +107,21 @@ pub struct Series<T> {
     pub values: Vec<T>,
 }
 
+#[derive(Deserialize, Debug)]
+#[doc(hidden)]
+pub struct TaggedReturn<TAG, T> {
+    #[serde(default = "Vec::new")]
+    pub series: Vec<TaggedSeries<TAG, T>>,
+}
+
+#[derive(Debug)]
+/// Represents a returned series from InfluxDB
+pub struct TaggedSeries<TAG, T> {
+    pub name: String,
+    pub tags: TAG,
+    pub values: Vec<T>,
+}
+
 impl Client {
     pub async fn json_query(&self, q: ReadQuery) -> Result<DatabaseQueryResult, Error> {
         let query = q.build().unwrap();

influxdb/tests/integration_tests.rs

@@ -358,6 +358,69 @@ async fn test_json_query() {
     .await;
 }
 
+/// INTEGRATION TEST
+///
+/// This test case tests whether the response to a GROUP BY can be parsed by
+// deserialize_next_tagged into a tags struct
+#[tokio::test]
+#[cfg(feature = "use-serde")]
+async fn test_json_query_tagged() {
+    use serde::Deserialize;
+
+    const TEST_NAME: &str = "test_json_query_tagged";
+
+    run_test(
+        || async move {
+            create_db(TEST_NAME).await.expect("could not setup db");
+
+            let client = create_client(TEST_NAME);
+
+            let write_query = Timestamp::Hours(11)
+                .into_query("weather")
+                .add_tag("location", "London")
+                .add_field("temperature", 82);
+            let write_result = client.query(&write_query).await;
+            assert_result_ok(&write_result);
+
+            #[derive(Deserialize, Debug, PartialEq)]
+            struct WeatherMeta {
+                location: String,
+            }
+
+            #[derive(Deserialize, Debug, PartialEq)]
+            struct Weather {
+                time: String,
+                temperature: i32,
+            }
+
+            let query = Query::raw_read_query("SELECT * FROM weather GROUP BY location");
+            let result = client.json_query(query).await.and_then(|mut db_result| {
+                db_result.deserialize_next_tagged::<WeatherMeta, Weather>()
+            });
+            assert_result_ok(&result);
+            let result = result.unwrap();
+
+            assert_eq!(
+                result.series[0].tags,
+                WeatherMeta {
+                    location: "London".to_string(),
+                }
+            );
+            assert_eq!(
+                result.series[0].values[0],
+                Weather {
+                    time: "1970-01-01T11:00:00Z".to_string(),
+                    temperature: 82
+                }
+            );
+        },
+        || async move {
+            delete_db(TEST_NAME).await.expect("could not clean up db");
+        },
+    )
+    .await;
+}
+
 /// INTEGRATION TEST
 ///
 /// This test case tests whether JSON can be decoded from a InfluxDB response and wether that JSON