chore: add KVPbApi::get_pb_stream() but it is not yet ready for produ…

…ction use (databendlabs#15471)

src/meta/api/src/kv_pb_api/mod.rs

@@ -127,6 +127,112 @@ pub trait KVPbApi: KVApi {
         }
     }
 
+    /// Same as `get_pb_stream` but does not return keys, only values.
+    #[deprecated(note = "stream may be closed. The caller must check it")]
+    fn get_pb_values<K, I>(
+        &self,
+        keys: I,
+    ) -> impl Future<
+        Output = Result<
+            BoxStream<
+                'static, //
+                Result<Option<SeqV<K::ValueType>>, Self::Error>,
+            >,
+            Self::Error,
+        >,
+    > + Send
+    where
+        K: kvapi::Key + 'static,
+        K::ValueType: FromToProto + Send + 'static,
+        I: IntoIterator<Item = K>,
+        Self::Error: From<PbApiReadError<Self::Error>>,
+    {
+        self.get_pb_stream_low(keys)
+            // This `map()` handles Future result
+            .map(|r| match r {
+                Ok(strm) => {
+                    // These two `map_xx()` handles Stream result
+                    Ok(strm.map_ok(|(_k, v)| v).map_err(Self::Error::from).boxed())
+                }
+                Err(e) => Err(e),
+            })
+    }
+
+    /// Get protobuf encoded values by a series of kvapi::Key.
+    ///
+    /// The key will be converted to string and the returned value is decoded by `FromToProto`.
+    /// It returns the same error as `KVApi::Error`,
+    /// thus it requires KVApi::Error can describe a decoding error, i.e., `impl From<PbApiReadError>`.
+    #[deprecated(note = "stream may be closed. The caller must check it")]
+    fn get_pb_stream<K, I>(
+        &self,
+        keys: I,
+    ) -> impl Future<
+        Output = Result<
+            BoxStream<
+                'static, //
+                Result<(K, Option<SeqV<K::ValueType>>), Self::Error>,
+            >,
+            Self::Error,
+        >,
+    > + Send
+    where
+        K: kvapi::Key + 'static,
+        K::ValueType: FromToProto + Send + 'static,
+        I: IntoIterator<Item = K>,
+        Self::Error: From<PbApiReadError<Self::Error>>,
+    {
+        self.get_pb_stream_low(keys).map(|r| match r {
+            Ok(strm) => Ok(strm.map_err(Self::Error::from).boxed()),
+            Err(e) => Err(e),
+        })
+    }
+
+    /// Same as `get_pb_stream` but returns [`PbApiReadError`]. No require of `From<PbApiReadError>` for `Self::Error`.
+    fn get_pb_stream_low<K, I>(
+        &self,
+        keys: I,
+    ) -> impl Future<
+        Output = Result<
+            BoxStream<
+                'static, //
+                Result<(K, Option<SeqV<K::ValueType>>), PbApiReadError<Self::Error>>,
+            >,
+            Self::Error,
+        >,
+    > + Send
+    where
+        K: kvapi::Key + 'static,
+        K::ValueType: FromToProto + Send + 'static,
+        I: IntoIterator<Item = K>,
+    {
+        let keys = keys
+            .into_iter()
+            .map(|k| kvapi::Key::to_string_key(&k))
+            .collect::<Vec<_>>();
+
+        async move {
+            let strm = self.get_kv_stream(&keys).await?;
+
+            let strm = strm.map(|r: Result<StreamItem, Self::Error>| {
+                let item = r.map_err(PbApiReadError::KvApiError)?;
+
+                let k = K::from_str_key(&item.key).map_err(PbApiReadError::KeyError)?;
+
+                let v = if let Some(pb_seqv) = item.value {
+                    let seqv = decode_seqv::<K::ValueType>(SeqV::from(pb_seqv))?;
+                    Some(seqv)
+                } else {
+                    None
+                };
+
+                Ok((k, v))
+            });
+
+            Ok(strm.boxed())
+        }
+    }
+
     /// Same as `list_pb` but does not return values, only keys.
     fn list_pb_keys<K>(
         &self,
@@ -216,3 +322,164 @@ pub trait KVPbApi: KVApi {
 }
 
 impl<T> KVPbApi for T where T: KVApi + ?Sized {}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::BTreeMap;
+
+    use async_trait::async_trait;
+    use chrono::DateTime;
+    use chrono::Utc;
+    use databend_common_meta_app::schema::CatalogIdIdent;
+    use databend_common_meta_app::schema::CatalogMeta;
+    use databend_common_meta_app::schema::CatalogOption;
+    use databend_common_meta_app::schema::HiveCatalogOption;
+    use databend_common_meta_app::storage::StorageS3Config;
+    use databend_common_meta_app::tenant::Tenant;
+    use databend_common_meta_kvapi::kvapi::KVApi;
+    use databend_common_meta_kvapi::kvapi::KVStream;
+    use databend_common_meta_kvapi::kvapi::UpsertKVReply;
+    use databend_common_meta_kvapi::kvapi::UpsertKVReq;
+    use databend_common_meta_types::protobuf::StreamItem;
+    use databend_common_meta_types::MetaError;
+    use databend_common_meta_types::SeqV;
+    use databend_common_meta_types::SeqValue;
+    use databend_common_meta_types::TxnReply;
+    use databend_common_meta_types::TxnRequest;
+    use databend_common_proto_conv::FromToProto;
+    use futures::StreamExt;
+    use futures::TryStreamExt;
+    use prost::Message;
+
+    use crate::kv_pb_api::KVPbApi;
+
+    //
+    struct Foo {
+        kvs: BTreeMap<String, SeqV>,
+    }
+
+    #[async_trait]
+    impl KVApi for Foo {
+        type Error = MetaError;
+
+        async fn upsert_kv(&self, _req: UpsertKVReq) -> Result<UpsertKVReply, Self::Error> {
+            todo!()
+        }
+
+        async fn get_kv_stream(
+            &self,
+            keys: &[String],
+        ) -> Result<KVStream<Self::Error>, Self::Error> {
+            let mut res = Vec::with_capacity(keys.len());
+            for key in keys {
+                let k = key.clone();
+                let v = self.kvs.get(key).cloned();
+
+                let item = StreamItem::new(k, v.map(|v| v.into()));
+                res.push(Ok(item));
+            }
+
+            let strm = futures::stream::iter(res);
+            Ok(strm.boxed())
+        }
+
+        async fn list_kv(&self, _prefix: &str) -> Result<KVStream<Self::Error>, Self::Error> {
+            todo!()
+        }
+
+        async fn transaction(&self, _txn: TxnRequest) -> Result<TxnReply, Self::Error> {
+            todo!()
+        }
+    }
+
+    // TODO: test upsert_kv
+    // TODO: test upsert_kv
+    // TODO: test list_kv
+
+    #[tokio::test]
+    async fn test_mget() -> anyhow::Result<()> {
+        let catalog_meta = CatalogMeta {
+            catalog_option: CatalogOption::Hive(HiveCatalogOption {
+                address: "127.0.0.1:10000".to_string(),
+                storage_params: Some(Box::new(
+                    databend_common_meta_app::storage::StorageParams::S3(StorageS3Config {
+                        endpoint_url: "http://127.0.0.1:9900".to_string(),
+                        region: "hello".to_string(),
+                        bucket: "world".to_string(),
+                        access_key_id: "databend_has_super_power".to_string(),
+                        secret_access_key: "databend_has_super_power".to_string(),
+                        ..Default::default()
+                    }),
+                )),
+            }),
+            created_on: DateTime::<Utc>::MIN_UTC,
+        };
+        let v = catalog_meta.to_pb()?.encode_to_vec();
+
+        let foo = Foo {
+            kvs: vec![
+                (s("__fd_catalog_by_id/1"), SeqV::new(1, v.clone())),
+                (s("__fd_catalog_by_id/2"), SeqV::new(2, v.clone())),
+                (s("__fd_catalog_by_id/3"), SeqV::new(3, v.clone())),
+            ]
+            .into_iter()
+            .collect(),
+        };
+
+        let tenant = Tenant::new_literal("dummy");
+
+        // Get key value pairs
+        {
+            #[allow(deprecated)]
+            let strm = foo
+                .get_pb_stream([
+                    CatalogIdIdent::new(&tenant, 1),
+                    CatalogIdIdent::new(&tenant, 2),
+                    CatalogIdIdent::new(&tenant, 4),
+                ])
+                .await?;
+
+            let got = strm.try_collect::<Vec<_>>().await?;
+
+            assert_eq!(CatalogIdIdent::new(&tenant, 1), got[0].0);
+            assert_eq!(CatalogIdIdent::new(&tenant, 2), got[1].0);
+            assert_eq!(CatalogIdIdent::new(&tenant, 4), got[2].0);
+
+            assert_eq!(1, got[0].1.seq());
+            assert_eq!(2, got[1].1.seq());
+            assert_eq!(0, got[2].1.seq());
+
+            assert_eq!(Some(&catalog_meta), got[0].1.value());
+            assert_eq!(Some(&catalog_meta), got[1].1.value());
+            assert_eq!(None, got[2].1.value());
+        }
+
+        // Get values
+        {
+            #[allow(deprecated)]
+            let strm = foo
+                .get_pb_values([
+                    CatalogIdIdent::new(&tenant, 1),
+                    CatalogIdIdent::new(&tenant, 2),
+                    CatalogIdIdent::new(&tenant, 4),
+                ])
+                .await?;
+
+            let got = strm.try_collect::<Vec<_>>().await?;
+
+            assert_eq!(1, got[0].seq());
+            assert_eq!(2, got[1].seq());
+            assert_eq!(0, got[2].seq());
+
+            assert_eq!(Some(&catalog_meta), got[0].value());
+            assert_eq!(Some(&catalog_meta), got[1].value());
+            assert_eq!(None, got[2].value());
+        }
+
+        Ok(())
+    }
+
+    fn s(x: impl ToString) -> String {
+        x.to_string()
+    }
+}