feat(cubesql): Support performance_schema.session_variables & global_…

…variables

rust/cubesql/src/compile/engine/information_schema/mod.rs

@@ -1,3 +1,4 @@
 pub mod columns;
 pub mod statistics;
 pub mod tables;
+pub mod variables;

rust/cubesql/src/compile/engine/information_schema/tables.rs

@@ -157,6 +157,8 @@ impl InfoSchemaTableProvider {
         let mut builder = InformationSchemaTablesBuilder::new();
         builder.add_table("def", "information_schema", "tables");
         builder.add_table("def", "information_schema", "columns");
+        builder.add_table("def", "performance_schema", "session_variables");
+        builder.add_table("def", "performance_schema", "global_variables");
 
         for cube in cubes {
             builder.add_table("def", "db", cube.name.clone());

rust/cubesql/src/compile/engine/information_schema/variables.rs

@@ -0,0 +1,80 @@
+use std::{any::Any, collections::HashMap, sync::Arc};
+
+use async_trait::async_trait;
+use datafusion::{
+    arrow::{
+        array::{Array, StringBuilder},
+        datatypes::{DataType, Field, Schema, SchemaRef},
+        record_batch::RecordBatch,
+    },
+    datasource::{datasource::TableProviderFilterPushDown, TableProvider, TableType},
+    error::DataFusionError,
+    logical_plan::Expr,
+    physical_plan::{memory::MemoryExec, ExecutionPlan},
+};
+
+pub struct PerfSchemaVariablesProvider {
+    variables: HashMap<String, String>,
+}
+
+impl PerfSchemaVariablesProvider {
+    pub fn new() -> Self {
+        let mut variables = HashMap::new();
+        variables.insert("max_allowed_packet".to_string(), "67108864".to_string());
+
+        Self { variables }
+    }
+}
+
+#[async_trait]
+impl TableProvider for PerfSchemaVariablesProvider {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn table_type(&self) -> TableType {
+        TableType::View
+    }
+
+    fn schema(&self) -> SchemaRef {
+        Arc::new(Schema::new(vec![
+            Field::new("VARIABLE_NAME", DataType::Utf8, false),
+            Field::new("VARIABLE_VALUE", DataType::Utf8, false),
+        ]))
+    }
+
+    async fn scan(
+        &self,
+        projection: &Option<Vec<usize>>,
+        _batch_size: usize,
+        _filters: &[Expr],
+        _limit: Option<usize>,
+    ) -> Result<Arc<dyn ExecutionPlan>, DataFusionError> {
+        let mut names = StringBuilder::new(100);
+        let mut values = StringBuilder::new(100);
+
+        for (key, value) in self.variables.iter() {
+            names.append_value(key.clone()).unwrap();
+            values.append_value(value.clone()).unwrap();
+        }
+
+        let mut data: Vec<Arc<dyn Array>> = vec![];
+        data.push(Arc::new(names.finish()));
+        data.push(Arc::new(values.finish()));
+
+        let batch = RecordBatch::try_new(self.schema(), data)?;
+
+        Ok(Arc::new(MemoryExec::try_new(
+            &[vec![batch]],
+            self.schema(),
+            projection.clone(),
+        )?))
+    }
+
+    fn supports_filter_pushdown(
+        &self,
+        _filter: &Expr,
+    ) -> Result<TableProviderFilterPushDown, DataFusionError> {
+        Ok(TableProviderFilterPushDown::Unsupported)
+    }
+}

rust/cubesql/src/compile/engine/provider.rs

@@ -10,7 +10,7 @@ use datafusion::{
 
 use super::information_schema::{
     columns::InfoSchemaColumnsProvider, statistics::InfoSchemaStatisticsProvider,
-    tables::InfoSchemaTableProvider,
+    tables::InfoSchemaTableProvider, variables::PerfSchemaVariablesProvider,
 };
 
 pub struct CubeContext<'a> {
@@ -55,6 +55,14 @@ impl<'a> ContextProvider for CubeContext<'a> {
             if tp.eq_ignore_ascii_case("information_schema.statistics") {
                 return Some(Arc::new(InfoSchemaStatisticsProvider::new()));
             }
+
+            if tp.eq_ignore_ascii_case("performance_schema.global_variables") {
+                return Some(Arc::new(PerfSchemaVariablesProvider::new()));
+            }
+
+            if tp.eq_ignore_ascii_case("performance_schema.session_variables") {
+                return Some(Arc::new(PerfSchemaVariablesProvider::new()));
+            }
         };
 
         None

rust/cubesql/src/compile/mod.rs

@@ -1256,7 +1256,9 @@ impl QueryPlanner {
             }
         };
 
-        if schema_name.to_lowercase() == "information_schema" {
+        if schema_name.to_lowercase() == "information_schema"
+            || schema_name.to_lowercase() == "performance_schema"
+        {
             return self.create_df_logical_plan(stmt.clone(), props);
         }
 
@@ -3067,6 +3069,8 @@ mod tests {
             +---------------+--------------------+---------------------------+------------+--------+---------+------------+-------------+----------------+-------------+-----------------+--------------+-----------+----------------+-------------+-------------+------------+-----------------+----------+----------------+---------------+\n\
             | def           | information_schema | tables                    | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
             | def           | information_schema | columns                   | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
+            | def           | performance_schema | session_variables         | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
+            | def           | performance_schema | global_variables          | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
             | def           | db                 | KibanaSampleDataEcommerce | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
             | def           | db                 | Logs                      | BASE TABLE | InnoDB | 10      | Dynamic    | 0           | 0              | 16384       |                 |              |           |                |             |             |            |                 |          |                |               |\n\
             +---------------+--------------------+---------------------------+------------+--------+---------+------------+-------------+----------------+-------------+-----------------+--------------+-----------+----------------+-------------+-------------+------------+-----------------+----------+----------------+---------------+"
@@ -3109,4 +3113,27 @@ mod tests {
 
         Ok(())
     }
+
+    #[tokio::test]
+    async fn test_performance_schema_variables() -> Result<(), CubeError> {
+        assert_eq!(
+            execute_df_query("SELECT * FROM performance_schema.session_variables WHERE VARIABLE_NAME = 'max_allowed_packet'".to_string()).await?,
+            "+--------------------+----------------+\n\
+            | VARIABLE_NAME      | VARIABLE_VALUE |\n\
+            +--------------------+----------------+\n\
+            | max_allowed_packet | 67108864       |\n\
+            +--------------------+----------------+"
+        );
+
+        assert_eq!(
+            execute_df_query("SELECT * FROM performance_schema.global_variables WHERE VARIABLE_NAME = 'max_allowed_packet'".to_string()).await?,
+            "+--------------------+----------------+\n\
+            | VARIABLE_NAME      | VARIABLE_VALUE |\n\
+            +--------------------+----------------+\n\
+            | max_allowed_packet | 67108864       |\n\
+            +--------------------+----------------+"
+        );
+
+        Ok(())
+    }
 }