Add parquet_index_advanced.rs example of indexin into parquet files

Author: alamb

datafusion-examples/README.md

@@ -61,6 +61,7 @@ cargo run --example csv_sql
 - [`make_date.rs`](examples/make_date.rs): Examples of using the make_date function
 - [`memtable.rs`](examples/memtable.rs): Create an query data in memory using SQL and `RecordBatch`es
 - ['parquet_index.rs'](examples/parquet_index.rs): Create an secondary index over several parquet files and use it to speed up queries
+- ['parquet_index_advanced.rs'](examples/parquet_index.rs): Create a detailed secondary index that covers the contents of several parquet files
 - [`parquet_sql.rs`](examples/parquet_sql.rs): Build and run a query plan from a SQL statement against a local Parquet file
 - [`parquet_sql_multiple_files.rs`](examples/parquet_sql_multiple_files.rs): Build and run a query plan from a SQL statement against multiple local Parquet files
 - ['parquet_exec_visitor.rs'](examples/parquet_exec_visitor.rs): Extract statistics by visiting an ExecutionPlan after execution