Refactor: Use template rendering and explicit prepare function

for preparing queries in the middle

Author: joto

src/middle-pgsql.cpp

@@ -130,8 +130,7 @@ std::vector<std::string> build_sql(options_t const &options,
 
 middle_pgsql_t::table_desc::table_desc(options_t const &options,
                                        table_sql const &ts)
-: m_prepare_queries(build_sql(options, ts.prepare_queries)),
-  m_copy_target(std::make_shared<db_target_descr_t>(
+: m_copy_target(std::make_shared<db_target_descr_t>(
       options.middle_dbschema, build_sql(options, ts.name), "id"))
 {
     m_create_fw_dep_indexes = build_sql(options, ts.create_fw_dep_indexes);
@@ -149,9 +148,10 @@ void middle_pgsql_t::dbexec(std::string_view templ) const
     m_db_connection.exec(render_template(templ));
 }
 
-void middle_query_pgsql_t::exec_sql(std::string const &sql_cmd) const
+void middle_query_pgsql_t::prepare(std::string_view stmt,
+                                   std::string const &sql_cmd) const
 {
-    m_db_connection.exec(sql_cmd);
+    m_db_connection.prepare(stmt, fmt::runtime(sql_cmd));
 }
 
 void middle_pgsql_t::table_desc::drop_table(
@@ -1203,16 +1203,6 @@ table_sql sql_for_nodes(middle_pgsql_options const &options)
 
     sql.name = "{prefix}_nodes";
 
-    if (options.nodes) {
-        sql.prepare_queries = {
-            "PREPARE get_node_list(int8[]) AS"
-            " SELECT id, lon, lat FROM {schema}\"{prefix}_nodes\""
-            " WHERE id = ANY($1::int8[])",
-            "PREPARE get_node(int8) AS"
-            " SELECT id, lon, lat FROM {schema}\"{prefix}_nodes\""
-            " WHERE id = $1"};
-    }
-
     return sql;
 }
 
@@ -1222,17 +1212,6 @@ table_sql sql_for_ways()
 
     sql.name = "{prefix}_ways";
 
-    sql.prepare_queries = {"PREPARE get_way(int8) AS"
-                           " SELECT nodes, tags{attribute_columns_use}"
-                           " FROM {schema}\"{prefix}_ways\" o"
-                           " {users_table_access}"
-                           " WHERE o.id = $1",
-                           "PREPARE get_way_list(int8[]) AS"
-                           " SELECT o.id, nodes, tags{attribute_columns_use}"
-                           " FROM {schema}\"{prefix}_ways\" o"
-                           "  {users_table_access}"
-                           " WHERE o.id = ANY($1::int8[])"};
-
     sql.create_fw_dep_indexes = {
         "CREATE OR REPLACE FUNCTION"
         "    {schema}\"{prefix}_index_bucket\"(int8[])"
@@ -1254,12 +1233,6 @@ table_sql sql_for_relations()
 
     sql.name = "{prefix}_rels";
 
-    sql.prepare_queries = {"PREPARE get_rel(int8) AS"
-                           " SELECT members, tags{attribute_columns_use}"
-                           " FROM {schema}\"{prefix}_rels\" o"
-                           " {users_table_access}"
-                           " WHERE o.id = $1"};
-
     sql.create_fw_dep_indexes = {
         "CREATE OR REPLACE FUNCTION"
         " {schema}\"{prefix}_member_ids\"(jsonb, char)"
@@ -1373,12 +1346,36 @@ middle_pgsql_t::get_query_instance()
         m_options->connection_params, m_cache, m_persistent_cache,
         m_store_options);
 
-    // We use a connection per table to enable the use of COPY
-    for (auto &table : m_tables) {
-        for (auto const &query : table.prepare_queries()) {
-            mid->exec_sql(query);
-        }
-    }
+    if (m_store_options.nodes) {
+        mid->prepare("get_node",
+                     render_template(
+                         "SELECT id, lon, lat FROM {schema}\"{prefix}_nodes\""
+                         " WHERE id = $1::int8"));
+
+        mid->prepare("get_node_list",
+                     render_template(
+                         "SELECT id, lon, lat FROM {schema}\"{prefix}_nodes\""
+                         " WHERE id = ANY($1::int8[])"));
+    }
+
+    mid->prepare("get_way",
+                 render_template("SELECT nodes, tags{attribute_columns_use}"
+                                 " FROM {schema}\"{prefix}_ways\" o"
+                                 " {users_table_access}"
+                                 " WHERE o.id = $1::int8"));
+
+    mid->prepare(
+        "get_way_list",
+        render_template("SELECT o.id, nodes, tags{attribute_columns_use}"
+                        " FROM {schema}\"{prefix}_ways\" o"
+                        "  {users_table_access}"
+                        " WHERE o.id = ANY($1::int8[])"));
+
+    mid->prepare("get_rel",
+                 render_template("SELECT members, tags{attribute_columns_use}"
+                                 " FROM {schema}\"{prefix}_rels\" o"
+                                 " {users_table_access}"
+                                 " WHERE o.id = $1::int8"));
 
     return std::shared_ptr<middle_query_t>(mid.release());
 }

src/middle-pgsql.hpp

@@ -71,7 +71,7 @@ class middle_query_pgsql_t : public middle_query_t
     bool relation_get(osmid_t id,
                       osmium::memory::Buffer *buffer) const override;
 
-    void exec_sql(std::string const &sql_cmd) const;
+    void prepare(std::string_view stmt, std::string const &sql_cmd) const;
 
 private:
     osmium::Location get_node_location_flatnodes(osmid_t id) const;
@@ -89,7 +89,6 @@ class middle_query_pgsql_t : public middle_query_t
 struct table_sql
 {
     std::string name;
-    std::vector<std::string> prepare_queries;
     std::vector<std::string> create_fw_dep_indexes;
 };
 
@@ -155,14 +154,8 @@ struct middle_pgsql_t : public middle_t
 
         osmid_t max_id() const noexcept { return m_max_id; }
 
-        std::vector<std::string> const &prepare_queries() const noexcept
-        {
-            return m_prepare_queries;
-        }
-
     private:
         std::vector<std::string> m_create_fw_dep_indexes;
-        std::vector<std::string> m_prepare_queries;
         std::shared_ptr<db_target_descr_t> m_copy_target;
         task_result_t m_task_result;