better exception message in delete table with projection

src/Interpreters/InterpreterDeleteQuery.cpp

@@ -25,6 +25,7 @@ namespace ErrorCodes
     extern const int TABLE_IS_READ_ONLY;
     extern const int SUPPORT_IS_DISABLED;
     extern const int BAD_ARGUMENTS;
+    extern const int NOT_IMPLEMENTED;
 }
 
 
@@ -107,7 +108,19 @@ BlockIO InterpreterDeleteQuery::execute()
     }
     else
     {
-        throw Exception(ErrorCodes::BAD_ARGUMENTS, "DELETE query is not supported for table {}", table->getStorageID().getFullTableName());
+        /// Currently just better exception for the case of a table with projection,
+        /// can act differently according to the setting.
+        if (table->hasProjection())
+        {
+            throw Exception(ErrorCodes::NOT_IMPLEMENTED,
+                "DELETE query is not supported for table {} as it has projections. "
+                "User should drop all the projections manually before running the query",
+                table->getStorageID().getFullTableName());
+        }
+
+        throw Exception(ErrorCodes::BAD_ARGUMENTS,
+            "DELETE query is not supported for table {}",
+            table->getStorageID().getFullTableName());
     }
 }
 

src/Storages/IStorage.h

@@ -259,6 +259,9 @@ public:
     /// Return true if storage can execute lightweight delete mutations.
     virtual bool supportsLightweightDelete() const { return false; }
 
+    /// Return true if storage has any projection.
+    virtual bool hasProjection() const { return false; }
+
     /// Return true if storage can execute 'DELETE FROM' mutations. This is different from lightweight delete
     /// because those are internally translated into 'ALTER UDPATE' mutations.
     virtual bool supportsDelete() const { return false; }

src/Storages/MergeTree/IMergeTreeDataPart.h

@@ -442,6 +442,8 @@ public:
 
     bool hasProjection(const String & projection_name) const { return projection_parts.contains(projection_name); }
 
+    bool hasProjection() const { return !projection_parts.empty(); }
+
     bool hasBrokenProjection(const String & projection_name) const;
 
     /// Return true, if all projections were loaded successfully and none was marked as broken.

src/Storages/MergeTree/MergeTreeData.cpp

@@ -6133,6 +6133,21 @@ bool MergeTreeData::supportsLightweightDelete() const
     return true;
 }
 
+bool MergeTreeData::hasProjection() const
+{
+    auto lock = lockParts();
+    for (const auto & part : data_parts_by_info)
+    {
+        if (part->getState() == MergeTreeDataPartState::Outdated
+            || part->getState() == MergeTreeDataPartState::Deleting)
+            continue;
+
+        if (part->hasProjection())
+            return true;
+    }
+    return false;
+}
+
 MergeTreeData::ProjectionPartsVector MergeTreeData::getAllProjectionPartsVector(MergeTreeData::DataPartStateVector * out_states) const
 {
     ProjectionPartsVector res;

src/Storages/MergeTree/MergeTreeData.h

@@ -438,6 +438,8 @@ public:
 
     bool supportsLightweightDelete() const override;
 
+    bool hasProjection() const override;
+
     bool areAsynchronousInsertsEnabled() const override { return getSettings()->async_insert; }
 
     bool supportsTrivialCountOptimization(const StorageSnapshotPtr &, ContextPtr) const override;

tests/queries/0_stateless/03161_lightweight_delete_projection.sql

@@ -0,0 +1,15 @@
+
+DROP TABLE IF EXISTS users;
+
+CREATE TABLE users (
+    uid Int16,
+    name String,
+    age Int16,
+    projection p1 (select count(), age group by age)
+) ENGINE = MergeTree order by uid;
+
+INSERT INTO users VALUES (1231, 'John', 33);
+INSERT INTO users VALUES (6666, 'Ksenia', 48);
+INSERT INTO users VALUES (8888, 'Alice', 50);
+
+DELETE FROM users WHERE 1; -- { serverError NOT_IMPLEMENTED }