Clean up pgsql code related to COPY command

Use consistent and somewhat clearer naming, use special function for
copy_start().

Author: joto

src/db-copy.cpp

@@ -184,7 +184,7 @@ void db_copy_thread_t::thread_t::write_to_db(db_cmd_copy_t *buffer)
         start_copy(buffer->target);
     }
 
-    m_conn->copy_data(buffer->buffer, buffer->target->name);
+    m_conn->copy_send(buffer->buffer, buffer->target->name);
 }
 
 void db_copy_thread_t::thread_t::start_copy(
@@ -205,15 +205,15 @@ void db_copy_thread_t::thread_t::start_copy(
     }
 
     sql.push_back('\0');
-    m_conn->query(PGRES_COPY_IN, sql.data());
+    m_conn->copy_start(sql.data());
 
     m_inflight = target;
 }
 
 void db_copy_thread_t::thread_t::finish_copy()
 {
     if (m_inflight) {
-        m_conn->end_copy(m_inflight->name);
+        m_conn->copy_end(m_inflight->name);
         m_inflight.reset();
     }
 }

src/pgsql.cpp

@@ -80,13 +80,25 @@ void pg_conn_t::exec(std::string const &sql) const
     }
 }
 
-void pg_conn_t::copy_data(std::string const &sql,
+void pg_conn_t::copy_start(char const *sql) const
+{
+    assert(m_conn);
+
+    log_sql("{}", sql);
+    pg_result_t const res{PQexec(m_conn.get(), sql)};
+    if (res.status() != PGRES_COPY_IN) {
+        throw std::runtime_error{
+            "Database error on COPY: {}"_format(error_msg())};
+    }
+}
+
+void pg_conn_t::copy_send(std::string const &data,
                           std::string const &context) const
 {
     assert(m_conn);
 
-    log_sql_data("Copy data to '{}':\n{}", context, sql);
-    int const r = PQputCopyData(m_conn.get(), sql.c_str(), (int)sql.size());
+    log_sql_data("Copy data to '{}':\n{}", context, data);
+    int const r = PQputCopyData(m_conn.get(), data.c_str(), (int)data.size());
 
     switch (r) {
     case 0: // need to wait for write ready
@@ -101,17 +113,17 @@ void pg_conn_t::copy_data(std::string const &sql,
         break;
     }
 
-    if (sql.size() < 1100) {
-        log_error("Data: {}", sql);
+    if (data.size() < 1100) {
+        log_error("Data: {}", data);
     } else {
-        log_error("Data: {}\n...\n{}", std::string(sql, 0, 500),
-                  std::string(sql, sql.size() - 500));
+        log_error("Data: {}\n...\n{}", std::string(data, 0, 500),
+                  std::string(data, data.size() - 500));
     }
 
     throw std::runtime_error{"COPYing data to Postgresql."};
 }
 
-void pg_conn_t::end_copy(std::string const &context) const
+void pg_conn_t::copy_end(std::string const &context) const
 {
     assert(m_conn);
 

src/pgsql.hpp

@@ -237,9 +237,9 @@ class pg_conn_t
     void exec(char const *sql) const;
     void exec(std::string const &sql) const;
 
-    void copy_data(std::string const &sql, std::string const &context) const;
-
-    void end_copy(std::string const &context) const;
+    void copy_start(char const *sql) const;
+    void copy_send(std::string const &data, std::string const &context) const;
+    void copy_end(std::string const &context) const;
 
     /// Return the latest generated error message on this connection.
     char const *error_msg() const noexcept;