Throw for alter and silence for drop

src/Disks/DiskWebServer.cpp

@@ -3,7 +3,7 @@
 #include <common/logger_useful.h>
 
 #include <IO/ReadWriteBufferFromHTTP.h>
-#include <IO/ReadIndirectBufferFromWebServer.h>
+#include <Disks/ReadIndirectBufferFromWebServer.h>
 #include <IO/SeekAvoidingReadBuffer.h>
 #include <IO/ReadHelpers.h>
 #include <IO/WriteHelpers.h>

src/Disks/DiskWebServer.h

@@ -93,6 +93,8 @@ public:
 
     const String & getPath() const final override { return metadata_path; }
 
+    bool isReadOnly() const override { return true; }
+
     UInt64 getTotalSpace() const final override { return std::numeric_limits<UInt64>::max(); }
 
     UInt64 getAvailableSpace() const final override { return std::numeric_limits<UInt64>::max(); }

src/Disks/IDisk.h

@@ -216,6 +216,8 @@ public:
     /// Overrode in remote fs disks.
     virtual bool supportZeroCopyReplication() const = 0;
 
+    virtual bool isReadOnly() const { return false; }
+
     /// Invoked when Global Context is shutdown.
     virtual void shutdown() {}
 

src/Disks/IDiskRemote.h

@@ -178,8 +178,6 @@ struct IDiskRemote::Metadata : RemoteMetadata
     static constexpr UInt32 VERSION_RELATIVE_PATHS = 2;
     static constexpr UInt32 VERSION_READ_ONLY_FLAG = 3;
 
-    using PathAndSize = std::pair<String, size_t>;
-
     /// Disk path.
     const String & disk_path;
 

src/Disks/ReadIndirectBufferFromRemoteFS.cpp

@@ -2,7 +2,7 @@
 
 #include <IO/ReadBufferFromS3.h>
 #include <Storages/HDFS/ReadBufferFromHDFS.h>
-#include <IO/ReadIndirectBufferFromWebServer.h>
+#include <Disks/ReadIndirectBufferFromWebServer.h>
 
 
 namespace DB

src/Disks/ReadIndirectBufferFromWebServer.cpp

@@ -58,6 +58,7 @@ bool ReadIndirectBufferFromWebServer::nextImpl()
 
     if (impl)
     {
+        /// Restore correct position at the needed offset.
         impl->position() = position();
         assert(!impl->hasPendingData());
     }

src/Interpreters/InterpreterAlterQuery.cpp

@@ -32,6 +32,7 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
     extern const int INCORRECT_QUERY;
     extern const int NOT_IMPLEMENTED;
+    extern const int TABLE_IS_READ_ONLY;
 }
 
 
@@ -62,6 +63,8 @@ BlockIO InterpreterAlterQuery::execute()
     }
 
     StoragePtr table = DatabaseCatalog::instance().getTable(table_id, getContext());
+    if (table->isReadOnly())
+        throw Exception(ErrorCodes::TABLE_IS_READ_ONLY, "Table is read-only");
     auto alter_lock = table->lockForAlter(getContext()->getCurrentQueryId(), getContext()->getSettingsRef().lock_acquire_timeout);
     auto metadata_snapshot = table->getInMemoryMetadataPtr();
 

src/Interpreters/InterpreterDropQuery.cpp

@@ -34,6 +34,7 @@ namespace ErrorCodes
     extern const int UNKNOWN_TABLE;
     extern const int NOT_IMPLEMENTED;
     extern const int INCORRECT_QUERY;
+    extern const int TABLE_IS_READ_ONLY;
 }
 
 
@@ -162,6 +163,8 @@ BlockIO InterpreterDropQuery::executeToTableImpl(ASTDropQuery & query, DatabaseP
         if (query.kind == ASTDropQuery::Kind::Detach)
         {
             getContext()->checkAccess(drop_storage, table_id);
+            if (table->isReadOnly())
+                throw Exception(ErrorCodes::TABLE_IS_READ_ONLY, "Table is read-only");
 
             if (table->isDictionary())
             {
@@ -195,6 +198,8 @@ BlockIO InterpreterDropQuery::executeToTableImpl(ASTDropQuery & query, DatabaseP
                 throw Exception("Cannot TRUNCATE dictionary", ErrorCodes::SYNTAX_ERROR);
 
             getContext()->checkAccess(AccessType::TRUNCATE, table_id);
+            if (table->isReadOnly())
+                throw Exception(ErrorCodes::TABLE_IS_READ_ONLY, "Table is read-only");
 
             table->checkTableCanBeDropped();
 

src/Storages/IStorage.cpp

@@ -201,6 +201,19 @@ NameDependencies IStorage::getDependentViewsByColumn(ContextPtr context) const
     return name_deps;
 }
 
+bool IStorage::isReadOnly() const
+{
+    auto storage_policy = getStoragePolicy();
+    if (storage_policy)
+    {
+        for (const auto disk : storage_policy->getDisks())
+            if (!disk->isReadOnly())
+                return false;
+        return true;
+    }
+    return false;
+}
+
 std::string PrewhereInfo::dump() const
 {
     WriteBufferFromOwnString ss;

src/Storages/IStorage.h

@@ -523,6 +523,9 @@ public:
     /// Returns storage policy if storage supports it.
     virtual StoragePolicyPtr getStoragePolicy() const { return {}; }
 
+    /// Returns true if all disks of storage are read-only.
+    virtual bool isReadOnly() const;
+
     /// If it is possible to quickly determine exact number of rows in the table at this moment of time, then return it.
     /// Used for:
     /// - Simple count() optimization

src/Storages/StorageMergeTree.cpp

@@ -241,6 +241,9 @@ void StorageMergeTree::checkTableCanBeDropped() const
 void StorageMergeTree::drop()
 {
     shutdown();
+    /// In case there is read-only disk we cannot allow to call dropAllData(), but dropping tables is allowed.
+    if (isReadOnly())
+        return;
     dropAllData();
 }
 

tests/integration/test_disk_over_web_server/test.py

@@ -60,3 +60,25 @@ def test_usage(cluster):
         node2.query("DROP TABLE test{}".format(i))
         print(f"Ok {i}")
 
+
+def test_incorrect_usage(cluster):
+    node1 = cluster.instances["node1"]
+    node2 = cluster.instances["node2"]
+    global uuids
+    node2.query("""
+        ATTACH TABLE test0 UUID '{}'
+        (id Int32) ENGINE = MergeTree() ORDER BY id
+        SETTINGS storage_policy = 'web';
+    """.format(uuids[0]))
+
+    result = node2.query("SELECT count() FROM test0")
+    assert(int(result) == 500000)
+
+    result = node2.query_and_get_error("ALTER TABLE test0 ADD COLUMN col1 Int32 first")
+    assert("Table is read-only" in result)
+
+    result = node2.query_and_get_error("TRUNCATE TABLE test0")
+    assert("Table is read-only" in result)
+
+    node2.query("DROP TABLE test0")
+