arrow_flight/sql/metadata/catalogs.rs
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use std::sync::Arc;
use arrow_array::{RecordBatch, StringArray};
use arrow_schema::{DataType, Field, Schema, SchemaRef};
use once_cell::sync::Lazy;
use crate::error::Result;
use crate::sql::CommandGetCatalogs;
/// A builder for a [`CommandGetCatalogs`] response.
///
/// Builds rows like this:
///
/// * catalog_name: utf8,
pub struct GetCatalogsBuilder {
catalogs: Vec<String>,
}
impl CommandGetCatalogs {
/// Create a builder suitable for constructing a response
pub fn into_builder(self) -> GetCatalogsBuilder {
self.into()
}
}
impl From<CommandGetCatalogs> for GetCatalogsBuilder {
fn from(_: CommandGetCatalogs) -> Self {
Self::new()
}
}
impl Default for GetCatalogsBuilder {
fn default() -> Self {
Self::new()
}
}
impl GetCatalogsBuilder {
/// Create a new instance of [`GetCatalogsBuilder`]
pub fn new() -> Self {
Self {
catalogs: Vec::new(),
}
}
/// Append a row
pub fn append(&mut self, catalog_name: impl Into<String>) {
self.catalogs.push(catalog_name.into());
}
/// builds a `RecordBatch` with the correct schema for a
/// [`CommandGetCatalogs`] response
pub fn build(self) -> Result<RecordBatch> {
let Self { catalogs } = self;
let batch = RecordBatch::try_new(
Arc::clone(&GET_CATALOG_SCHEMA),
vec![Arc::new(StringArray::from_iter_values(catalogs)) as _],
)?;
Ok(batch)
}
/// Returns the schema that will result from [`CommandGetCatalogs`]
///
/// [`CommandGetCatalogs`]: crate::sql::CommandGetCatalogs
pub fn schema(&self) -> SchemaRef {
get_catalogs_schema()
}
}
fn get_catalogs_schema() -> SchemaRef {
Arc::clone(&GET_CATALOG_SCHEMA)
}
/// The schema for GetCatalogs
static GET_CATALOG_SCHEMA: Lazy<SchemaRef> = Lazy::new(|| {
Arc::new(Schema::new(vec![Field::new(
"catalog_name",
DataType::Utf8,
false,
)]))
});