Add json=1 setting for explain actions

src/Interpreters/InterpreterExplainQuery.cpp

@@ -18,6 +18,9 @@
 #include <Processors/QueryPlan/BuildQueryPipelineSettings.h>
 #include <Processors/printPipeline.h>
 
+#include <boost/property_tree/ptree.hpp>
+#include <boost/property_tree/json_parser.hpp>
+
 namespace DB
 {
 
@@ -121,6 +124,7 @@ struct QueryPlanSettings
 
     /// Apply query plan optimizations.
     bool optimize = true;
+    bool json = false;
 
     constexpr static char name[] = "PLAN";
 
@@ -130,6 +134,7 @@ struct QueryPlanSettings
             {"description", query_plan_options.description},
             {"actions", query_plan_options.actions},
             {"optimize", optimize},
+            {"json", json}
     };
 };
 
@@ -255,6 +260,14 @@ BlockInputStreamPtr InterpreterExplainQuery::executeImpl()
         if (settings.optimize)
             plan.optimize(QueryPlanOptimizationSettings::fromContext(context));
 
+        if (settings.json)
+        {
+            auto tree = plan.explainPlan();
+            std::stringstream out;
+            boost::property_tree::json_parser::write_json(out, tree);
+            buf.str() = out.str();
+        }
+        else
             plan.explainPlan(buf, settings.query_plan_options);
     }
     else if (ast.getKind() == ASTExplainQuery::QueryPipeline)

src/Processors/QueryPlan/IQueryPlanStep.h

@@ -3,6 +3,8 @@
 #include <Core/SortDescription.h>
 #include <Processors/QueryPlan/BuildQueryPipelineSettings.h>
 
+#include <boost/property_tree/ptree_fwd.hpp>
+
 namespace DB
 {
 
@@ -96,6 +98,8 @@ public:
         const bool write_header = false;
     };
 
+    virtual void describeActions(boost::property_tree::ptree & /*tree*/) const {}
+
     /// Get detailed description of step actions. This is shown in EXPLAIN query with options `actions = 1`.
     virtual void describeActions(FormatSettings & /*settings*/) const {}
 

src/Processors/QueryPlan/QueryPlan.cpp

@@ -9,6 +9,7 @@
 #include <Processors/QueryPlan/Optimizations/Optimizations.h>
 #include <Processors/QueryPlan/Optimizations/QueryPlanOptimizationSettings.h>
 #include <Processors/QueryPlan/BuildQueryPipelineSettings.h>
+#include <boost/property_tree/ptree.hpp>
 
 namespace DB
 {
@@ -200,6 +201,65 @@ void QueryPlan::addInterpreterContext(std::shared_ptr<Context> context)
 }
 
 
+static boost::property_tree::ptree explainStep(const IQueryPlanStep & step)
+{
+    boost::property_tree::ptree tree;
+    tree.put("Node Type", step.getName());
+
+    const auto & description = step.getStepDescription();
+    if (!description.empty())
+        tree.put("Description", description);
+
+    step.describeActions(tree);
+
+    return tree;
+}
+
+boost::property_tree::ptree QueryPlan::explainPlan()
+{
+    checkInitialized();
+
+    struct Frame
+    {
+        Node * node;
+        size_t next_child = 0;
+        boost::property_tree::ptree node_tree = {};
+        boost::property_tree::ptree children_trees = {};
+    };
+
+    std::stack<Frame> stack;
+    stack.push(Frame{.node = root});
+
+    boost::property_tree::ptree tree;
+
+    while (!stack.empty())
+    {
+        auto & frame = stack.top();
+
+        if (frame.next_child == 0)
+            frame.node_tree = explainStep(*frame.node->step);
+
+        if (frame.next_child < frame.node->children.size())
+        {
+            stack.push(Frame{frame.node->children[frame.next_child]});
+            ++frame.next_child;
+        }
+        else
+        {
+            if (!frame.children_trees.empty())
+                frame.node_tree.add_child("Plans", frame.children_trees);
+
+            tree.swap(frame.node_tree);
+            stack.pop();
+
+            if (!stack.empty())
+                stack.top().children_trees.add_child("", tree);
+        }
+    }
+
+    return tree;
+}
+
 static void explainStep(
     const IQueryPlanStep & step,
     IQueryPlanStep::FormatSettings & settings,

src/Processors/QueryPlan/QueryPlan.h

@@ -3,6 +3,7 @@
 #include <list>
 #include <vector>
 #include <set>
+#include <boost/property_tree/ptree_fwd.hpp>
 
 #include <Core/Names.h>
 
@@ -73,6 +74,7 @@ public:
         bool header = false;
     };
 
+    boost::property_tree::ptree explainPlan();
     void explainPlan(WriteBuffer & buffer, const ExplainPlanOptions & options);
     void explainPipeline(WriteBuffer & buffer, const ExplainPipelineOptions & options);