Use has_extension/schema/tablespace() to create nicer error messages

This is currently for the flex output only. Backporting to pgsql output
is left as an exercise for the reader.

Author: joto

src/flex-table.cpp

@@ -10,6 +10,7 @@
 #include "flex-table.hpp"
 #include "format.hpp"
 #include "logging.hpp"
+#include "pgsql-capabilities.hpp"
 #include "pgsql-helper.hpp"
 #include "util.hpp"
 
@@ -189,6 +190,30 @@ void table_connection_t::start(bool append)
 {
     assert(m_db_connection);
 
+    if (!has_schema(*m_db_connection, table().schema())) {
+        throw std::runtime_error{
+            "Schema '{0}' not available. "
+            "Use 'CREATE SCHEMA \"{0}\";' to create it."_format(
+                table().schema())};
+    }
+
+    for (auto const &ts :
+         {table().data_tablespace(), table().index_tablespace()}) {
+        if (!has_tablespace(*m_db_connection, ts)) {
+            throw std::runtime_error{
+                "Tablespace '{0}' not available. "
+                "Use 'CREATE TABLESPACE \"{0}\" ...;' to create it."_format(
+                    ts)};
+        }
+    }
+
+    if (table().has_hstore_column()) {
+        if (!has_extension(*m_db_connection, "hstore")) {
+            throw std::runtime_error{"Extension 'hstore' not available. Use "
+                                     "'CREATE EXTENSION hstore;' to load it."};
+        }
+    }
+
     m_db_connection->exec("SET client_min_messages = WARNING");
 
     if (!append) {

src/flex-table.hpp

@@ -110,6 +110,14 @@ class flex_table_t
         return m_geom_column != std::numeric_limits<std::size_t>::max();
     }
 
+    bool has_hstore_column() const noexcept
+    {
+        auto const it = std::find_if(begin(), end(), [&](auto const &column) {
+            return column.type() == table_column_type::hstore;
+        });
+        return it != end();
+    }
+
     /// Get the (first, if there are multiple) geometry column.
     flex_table_column_t const &geom_column() const noexcept
     {