add config flag for recursive ctes

update docs from script

update slt test for doc change

datafusion/common/src/config.rs

@@ -278,6 +278,11 @@ config_namespace! {
         /// Hive. Note that this setting does not affect reading partitioned
         /// tables (e.g. `/table/year=2021/month=01/data.parquet`).
         pub listing_table_ignore_subdirectory: bool, default = true
+
+        /// Should DataFusion support recursive CTEs
+        /// Defaults to false since this feature is a work in progress and may not
+        /// behave as expected
+        pub enable_recursive_ctes: bool, default = false
     }
 }
 

datafusion/sql/src/query.rs

@@ -54,7 +54,18 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
             // Process CTEs from top to bottom
             // do not allow self-references
             if with.recursive {
-                return not_impl_err!("Recursive CTEs are not supported");
+                if self
+                    .context_provider
+                    .options()
+                    .execution
+                    .enable_recursive_ctes
+                {
+                    return plan_err!(
+                        "Recursive CTEs are enabled but are not yet supported"
+                    );
+                } else {
+                    return not_impl_err!("Recursive CTEs are not supported");
+                }
             }
 
             for cte in with.cte_tables {

datafusion/sqllogictest/test_files/information_schema.slt

@@ -150,6 +150,7 @@ datafusion.execution.aggregate.scalar_update_factor 10
 datafusion.execution.batch_size 8192
 datafusion.execution.coalesce_batches true
 datafusion.execution.collect_statistics false
+datafusion.execution.enable_recursive_ctes false
 datafusion.execution.listing_table_ignore_subdirectory true
 datafusion.execution.max_buffered_batches_per_output_file 2
 datafusion.execution.meta_fetch_concurrency 32
@@ -225,6 +226,7 @@ datafusion.execution.aggregate.scalar_update_factor 10 Specifies the threshold f
 datafusion.execution.batch_size 8192 Default batch size while creating new batches, it's especially useful for buffer-in-memory batches since creating tiny batches would result in too much metadata memory consumption
 datafusion.execution.coalesce_batches true When set to true, record batches will be examined between each operator and small batches will be coalesced into larger batches. This is helpful when there are highly selective filters or joins that could produce tiny output batches. The target batch size is determined by the configuration setting
 datafusion.execution.collect_statistics false Should DataFusion collect statistics after listing files
+datafusion.execution.enable_recursive_ctes false Should DataFusion support recursive CTEs Defaults to false since this feature is a work in progress and may not behave as expected
 datafusion.execution.listing_table_ignore_subdirectory true Should sub directories be ignored when scanning directories for data files. Defaults to true (ignores subdirectories), consistent with Hive. Note that this setting does not affect reading partitioned tables (e.g. `/table/year=2021/month=01/data.parquet`).
 datafusion.execution.max_buffered_batches_per_output_file 2 This is the maximum number of RecordBatches buffered for each output file being worked. Higher values can potentially give faster write performance at the cost of higher peak memory consumption
 datafusion.execution.meta_fetch_concurrency 32 Number of files to read in parallel when inferring schema and statistics

docs/source/user-guide/configs.md

@@ -83,6 +83,7 @@ Environment variables are read during `SessionConfig` initialisation so they mus
 | datafusion.execution.soft_max_rows_per_output_file                      | 50000000                  | Target number of rows in output files when writing multiple. This is a soft max, so it can be exceeded slightly. There also will be one file smaller than the limit if the total number of rows written is not roughly divisible by the soft max                                                                                                                                                                                                                                                                                                                                                        |
 | datafusion.execution.max_buffered_batches_per_output_file               | 2                         | This is the maximum number of RecordBatches buffered for each output file being worked. Higher values can potentially give faster write performance at the cost of higher peak memory consumption                                                                                                                                                                                                                                                                                                                                                                                                       |
 | datafusion.execution.listing_table_ignore_subdirectory                  | true                      | Should sub directories be ignored when scanning directories for data files. Defaults to true (ignores subdirectories), consistent with Hive. Note that this setting does not affect reading partitioned tables (e.g. `/table/year=2021/month=01/data.parquet`).                                                                                                                                                                                                                                                                                                                                         |
+| datafusion.execution.enable_recursive_ctes                              | false                     | Should DataFusion support recursive CTEs Defaults to false since this feature is a work in progress and may not behave as expected                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
 | datafusion.optimizer.enable_distinct_aggregation_soft_limit             | true                      | When set to true, the optimizer will push a limit operation into grouped aggregations which have no aggregate expressions, as a soft limit, emitting groups once the limit is reached, before all rows in the group are read.                                                                                                                                                                                                                                                                                                                                                                           |
 | datafusion.optimizer.enable_round_robin_repartition                     | true                      | When set to true, the physical plan optimizer will try to add round robin repartitioning to increase parallelism to leverage more CPU cores                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
 | datafusion.optimizer.enable_topk_aggregation                            | true                      | When set to true, the optimizer will attempt to perform limit operations during aggregations, if possible                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |