From 1fa123ee5c0a535d56eb0d12ea769a0409c0322a Mon Sep 17 00:00:00 2001
From: kssenii <sumarokovakseniia@mail.ru>
Date: Sat, 23 Oct 2021 01:33:17 +0300
Subject: [PATCH] Properly done

---
 .../PostgreSQL/DatabasePostgreSQL.cpp         | 21 +++++++++++++------
 .../fetchPostgreSQLTableStructure.cpp         | 12 +++++++++--
 .../PostgreSQLReplicationHandler.cpp          | 14 ++++++++++++-
 3 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/src/Databases/PostgreSQL/DatabasePostgreSQL.cpp b/src/Databases/PostgreSQL/DatabasePostgreSQL.cpp
index d671a2b87d7..5d3493d0c82 100644
--- a/src/Databases/PostgreSQL/DatabasePostgreSQL.cpp
+++ b/src/Databases/PostgreSQL/DatabasePostgreSQL.cpp
@@ -90,14 +90,23 @@ bool DatabasePostgreSQL::empty() const
 DatabaseTablesIteratorPtr DatabasePostgreSQL::getTablesIterator(ContextPtr local_context, const FilterByNameFunction & /* filter_by_table_name */) const
 {
     std::lock_guard<std::mutex> lock(mutex);
-
     Tables tables;
-    auto connection_holder = pool->get();
-    auto table_names = fetchPostgreSQLTablesList(connection_holder->get(), configuration.schema);
 
-    for (const auto & table_name : table_names)
-        if (!detached_or_dropped.count(table_name))
-            tables[table_name] = fetchTable(table_name, local_context, true);
+    /// Do not allow to throw here, because this might be, for example, a query to system.tables.
+    /// It must not fail on case of some postgres error.
+    try
+    {
+        auto connection_holder = pool->get();
+        auto table_names = fetchPostgreSQLTablesList(connection_holder->get(), configuration.schema);
+
+        for (const auto & table_name : table_names)
+            if (!detached_or_dropped.count(table_name))
+                tables[table_name] = fetchTable(table_name, local_context, true);
+    }
+    catch (...)
+    {
+        tryLogCurrentException(__PRETTY_FUNCTION__);
+    }
 
     return std::make_unique<DatabaseTablesSnapshotIterator>(tables, database_name);
 }
diff --git a/src/Databases/PostgreSQL/fetchPostgreSQLTableStructure.cpp b/src/Databases/PostgreSQL/fetchPostgreSQLTableStructure.cpp
index fd6b69e39f9..feb472fa152 100644
--- a/src/Databases/PostgreSQL/fetchPostgreSQLTableStructure.cpp
+++ b/src/Databases/PostgreSQL/fetchPostgreSQLTableStructure.cpp
@@ -191,7 +191,10 @@ std::shared_ptr<NamesAndTypesList> readNamesAndTypesList(
             columns[i] = NameAndTypePair(name_and_type.name, type);
         }
     }
-
+    catch (const pqxx::syntax_error & e)
+    {
+        throw Exception(ErrorCodes::BAD_ARGUMENTS, "Error: {} (in query: {})", e.what(), query);
+    }
     catch (const pqxx::undefined_table &)
     {
         throw Exception(ErrorCodes::UNKNOWN_TABLE, "PostgreSQL table {} does not exist", postgres_table);
@@ -213,7 +216,9 @@ PostgreSQLTableStructure fetchPostgreSQLTableStructure(
     PostgreSQLTableStructure table;
 
     auto where = fmt::format("relname = {}", quoteString(postgres_table));
-    if (!postgres_schema.empty())
+    if (postgres_schema.empty())
+        where += " AND relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = 'public')";
+    else
         where += fmt::format(" AND relnamespace = (SELECT oid FROM pg_namespace WHERE nspname = {})", quoteString(postgres_schema));
 
     std::string query = fmt::format(
@@ -225,6 +230,9 @@ PostgreSQLTableStructure fetchPostgreSQLTableStructure(
 
     table.columns = readNamesAndTypesList(tx, postgres_table, query, use_nulls, false);
 
+    if (!table.columns)
+        throw Exception(ErrorCodes::UNKNOWN_TABLE, "PostgreSQL table {} does not exist", postgres_table);
+
     if (with_primary_key)
     {
         /// wiki.postgresql.org/wiki/Retrieve_primary_key_columns
diff --git a/src/Storages/PostgreSQL/PostgreSQLReplicationHandler.cpp b/src/Storages/PostgreSQL/PostgreSQLReplicationHandler.cpp
index 3262a302f9f..670148e9baa 100644
--- a/src/Storages/PostgreSQL/PostgreSQLReplicationHandler.cpp
+++ b/src/Storages/PostgreSQL/PostgreSQLReplicationHandler.cpp
@@ -230,6 +230,8 @@ ASTPtr PostgreSQLReplicationHandler::getCreateNestedTableQuery(StorageMaterializ
     postgres::Connection connection(connection_info);
     pqxx::nontransaction tx(connection.getRef());
     auto table_structure = std::make_unique<PostgreSQLTableStructure>(fetchPostgreSQLTableStructure(tx, table_name, postgres_schema, true, true, true));
+    if (!table_structure)
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "Failed to get PostgreSQL table structure");
     return storage->getCreateNestedTableQuery(std::move(table_structure));
 }
 
@@ -649,7 +651,17 @@ PostgreSQLTableStructurePtr PostgreSQLReplicationHandler::fetchTableStructure(
     if (!is_materialized_postgresql_database)
         return nullptr;
 
-    return std::make_unique<PostgreSQLTableStructure>(fetchPostgreSQLTableStructure(tx, table_name, postgres_schema, true, true, true));
+    PostgreSQLTableStructure structure;
+    try
+    {
+        structure = fetchPostgreSQLTableStructure(tx, table_name, postgres_schema, true, true, true);
+    }
+    catch (...)
+    {
+        tryLogCurrentException(__PRETTY_FUNCTION__);
+    }
+
+    return std::make_unique<PostgreSQLTableStructure>(std::move(structure));
 }