[GitHub] [arrow-datafusion] jaylmiller commented on a diff in pull request #5326: Add example of catalog API usage (#5291)

["jaylmiller (via GitHub)" <gi...@apache.org>]

jaylmiller commented on code in PR #5326:
URL: https://github.com/apache/arrow-datafusion/pull/5326#discussion_r1111059678


##########
datafusion-examples/examples/catalog.rs:
##########
@@ -0,0 +1,287 @@
+// 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.
+
+//! Simple example of a catalog/schema implementation.
+//!
+//! Example requires git submodules to be initialized in repo as it uses data from
+//! the `parquet-testing` repo.
+use async_trait::async_trait;
+use datafusion::{
+    arrow::util::pretty,
+    catalog::{
+        catalog::{CatalogList, CatalogProvider},
+        schema::SchemaProvider,
+    },
+    datasource::{
+        file_format::{csv::CsvFormat, parquet::ParquetFormat, FileFormat},
+        listing::{ListingOptions, ListingTable, ListingTableConfig, ListingTableUrl},
+        TableProvider,
+    },
+    error::Result,
+    execution::context::SessionState,
+    prelude::SessionContext,
+};
+use std::sync::RwLock;
+use std::{
+    any::Any,
+    collections::HashMap,
+    path::{Path, PathBuf},
+    sync::Arc,
+};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let repo_dir = std::fs::canonicalize(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            // parent dir of datafusion-examples = repo root
+            .join(".."),
+    )
+    .unwrap();
+    let mut ctx = SessionContext::new();
+    let state = ctx.state();
+    let catlist = Arc::new(CustomCatalogList::new());
+    // use our custom catalog list for context. each context has a single catalog list.
+    // context will by default have MemoryCatalogList
+    ctx.register_catalog_list(catlist.clone());
+
+    // intitialize our catalog and schemas
+    let catalog = DirCatalog::new();
+    let parquet_schema = DirSchema::create(
+        &state,
+        DirSchemaOpts {
+            format: Arc::new(ParquetFormat::default()),
+            dir: &repo_dir.join("parquet-testing").join("data"),
+            ext: "parquet",
+        },
+    )
+    .await?;
+    let csv_schema = DirSchema::create(
+        &state,
+        DirSchemaOpts {
+            format: Arc::new(CsvFormat::default()),
+            dir: &repo_dir.join("testing").join("data").join("csv"),
+            ext: "csv",
+        },
+    )
+    .await?;
+    // register schemas into catalog
+    catalog.register_schema("parquet", parquet_schema.clone())?;
+    catalog.register_schema("csv", csv_schema.clone())?;
+    // register our catalog in the context
+    ctx.register_catalog("dircat", Arc::new(catalog));
+    {
+        // catalog was passed down into our custom catalog list since we overide the ctx's default
+        let catalogs = catlist.catalogs.read().unwrap();
+        assert!(catalogs.contains_key("dircat"));
+    };
+    let parquet_tables = {
+        let tables = parquet_schema.tables.read().unwrap();
+        tables.keys().take(5).cloned().collect::<Vec<_>>()

Review Comment:
   Good point. 5 was totally arbitrary to be honest. Wanted to show a few tables in the output but not fill up the user's entire screen with table results. I'll add that as a comment.



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