Mark Hybrid experimental

Signed-off-by: Mikhail Filimonov <mfilimonov@altinity.com>

Author: filimonov

docs/en/engines/table-engines/special/hybrid.md

@@ -22,6 +22,14 @@ Typical use cases include:
 
 By giving mutually exclusive predicates to the segments (for example, `date < watermark` and `date >= watermark`), you ensure that each row is read from exactly one source.
 
+## Enable the engine
+
+The Hybrid engine is experimental. Enable it per session (or in the user profile) before creating tables:
+
+```sql
+SET allow_experimental_hybrid_table = 1;
+```
+
 ## Engine definition
 
 ```sql

src/Core/Settings.cpp

@@ -7337,6 +7337,9 @@ Enable experimental hash functions
 Allows creation of tables with the [TimeSeries](../../engines/table-engines/integrations/time-series.md) table engine. Possible values:
 - 0 — the [TimeSeries](../../engines/table-engines/integrations/time-series.md) table engine is disabled.
 - 1 — the [TimeSeries](../../engines/table-engines/integrations/time-series.md) table engine is enabled.
+)", EXPERIMENTAL) \
+    DECLARE(Bool, allow_experimental_hybrid_table, false, R"(
+Allows creation of tables with the [Hybrid](../../engines/table-engines/special/hybrid.md) table engine.
 )", EXPERIMENTAL) \
     DECLARE(Bool, allow_experimental_codecs, false, R"(
 If it is set to true, allow to specify experimental compression codecs (but we don't have those yet and this option does nothing).

src/Core/SettingsChangesHistory.cpp

@@ -275,6 +275,7 @@ const VersionToSettingsChangesMap & getSettingsChangesHistory()
             {"allow_experimental_ytsaurus_table_engine", false, false, "New setting."},
             {"allow_experimental_ytsaurus_table_function", false, false, "New setting."},
             {"allow_experimental_ytsaurus_dictionary_source", false, false, "New setting."},
+            {"allow_experimental_hybrid_table", false, false, "Added new setting to allow the Hybrid table engine."},
             {"per_part_index_stats", false, false, "New setting."},
             {"allow_experimental_iceberg_compaction", 0, 0, "New setting"},
             {"delta_lake_snapshot_version", -1, -1, "New setting"},

src/Databases/enableAllExperimentalSettings.cpp

@@ -56,6 +56,7 @@ void enableAllExperimentalSettings(ContextMutablePtr context)
     context->setSetting("allow_experimental_ytsaurus_table_engine", 1);
     context->setSetting("allow_experimental_ytsaurus_dictionary_source", 1);
     context->setSetting("allow_experimental_time_series_aggregate_functions", 1);
+    context->setSetting("allow_experimental_hybrid_table", 1);
     context->setSetting("allow_experimental_lightweight_update", 1);
     context->setSetting("allow_experimental_insert_into_iceberg", 1);
     context->setSetting("allow_experimental_iceberg_compaction", 1);

src/Storages/StorageDistributed.cpp

@@ -201,6 +201,7 @@ namespace Setting
     extern const SettingsUInt64 allow_experimental_parallel_reading_from_replicas;
     extern const SettingsBool prefer_global_in_and_join;
     extern const SettingsBool enable_global_with_statement;
+    extern const SettingsBool allow_experimental_hybrid_table;
 }
 
 namespace DistributedSetting
@@ -234,6 +235,7 @@ namespace ErrorCodes
     extern const int DISTRIBUTED_TOO_MANY_PENDING_BYTES;
     extern const int ARGUMENT_OUT_OF_BOUND;
     extern const int TOO_LARGE_DISTRIBUTED_DEPTH;
+    extern const int SUPPORT_IS_DISABLED;
 }
 
 namespace ActionLocks
@@ -2258,8 +2260,6 @@ void registerStorageDistributed(StorageFactory & factory)
 
 void registerStorageHybrid(StorageFactory & factory)
 {
-    // Register Hybrid engine
-    // TODO: consider moving it to a separate file / subclass of StorageDistributed
     factory.registerStorage("Hybrid", [](const StorageFactory::Arguments & args) -> StoragePtr
     {
         ASTs & engine_args = args.engine_args;
@@ -2273,6 +2273,13 @@ void registerStorageHybrid(StorageFactory & factory)
         if (!local_context)
             local_context = global_context;
 
+        if (args.mode <= LoadingStrictnessLevel::CREATE
+            && !local_context->getSettingsRef()[Setting::allow_experimental_hybrid_table])
+        {
+            throw Exception(ErrorCodes::SUPPORT_IS_DISABLED,
+                "Experimental Hybrid table engine is not enabled (the setting 'allow_experimental_hybrid_table')");
+        }
+
         // Validate first argument - must be a table function
         ASTPtr first_arg = engine_args[0];
         if (const auto * func = first_arg->as<ASTFunction>())

tests/queries/0_stateless/03642_hybrid.sql

@@ -1,4 +1,10 @@
--- Test Hybrid engine registration and basic validation
+SELECT 'Hybrid creation requires allow_experimental_hybrid_table';
+SET allow_experimental_hybrid_table = 0;
+CREATE TABLE test_hybrid_requires_setting (`dummy` UInt8) ENGINE = Hybrid(remote('localhost:9000'), 1); -- { serverError SUPPORT_IS_DISABLED }
+DROP TABLE IF EXISTS test_hybrid_requires_setting SYNC;
+
+SET allow_experimental_hybrid_table = 1;
+
 SELECT 'Check Hybrid engine is registered';
 SELECT name FROM system.table_engines WHERE name = 'Hybrid';
 

tests/queries/0_stateless/04182_hybrid_unqualified_table.sql

@@ -1,3 +1,5 @@
+SET allow_experimental_hybrid_table = 1;
+
 SELECT 'Hybrid allows unqualified local tables by default';
 
 DROP TABLE IF EXISTS test_hybrid_unqualified_segment SYNC;