Remove pg_conn_t::query() function, use pg_conn_t::exec() instead

This removes the pg_conn_t::query() in favour of the pg_conn_t::exec()
function. They mostly did the same thing anyway and it was always
confusing when to use which one and how to set the "expect" parameter.

Now we have exec() and exec_prepared() as the only functions running a
SQL command and returning the results.

Author: joto

src/middle-pgsql.cpp

@@ -826,8 +826,7 @@ static table_sql sql_for_relations() noexcept
 static bool check_bucket_index(pg_conn_t *db_connection,
                                std::string const &prefix)
 {
-    auto const res = db_connection->query(
-        PGRES_TUPLES_OK,
+    auto const res = db_connection->exec(
         "SELECT relname FROM pg_class WHERE relkind='i' AND"
         "  relname = '{}_ways_nodes_bucket_idx';"_format(prefix));
     return res.num_tuples() > 0;

src/pgsql-capabilities.cpp

@@ -32,8 +32,7 @@ static void init_set_from_query(std::set<std::string> *set,
                                 char const *table, char const *column,
                                 char const *condition = "true")
 {
-    auto const res = db_connection.query(
-        PGRES_TUPLES_OK,
+    auto const res = db_connection.exec(
         "SELECT {} FROM {} WHERE {}"_format(column, table, condition));
     for (int i = 0; i < res.num_tuples(); ++i) {
         set->emplace(res.get(i, 0));
@@ -43,8 +42,8 @@ static void init_set_from_query(std::set<std::string> *set,
 /// Get all config settings from the database.
 static void init_settings(pg_conn_t const &db_connection)
 {
-    auto const res = db_connection.query(
-        PGRES_TUPLES_OK, "SELECT name, setting FROM pg_settings");
+    auto const res =
+        db_connection.exec("SELECT name, setting FROM pg_settings");
 
     for (int i = 0; i < res.num_tuples(); ++i) {
         capabilities().settings.emplace(res.get(i, 0), res.get(i, 1));
@@ -53,8 +52,7 @@ static void init_settings(pg_conn_t const &db_connection)
 
 static void init_database_name(pg_conn_t const &db_connection)
 {
-    auto const res =
-        db_connection.query(PGRES_TUPLES_OK, "SELECT current_catalog");
+    auto const res = db_connection.exec("SELECT current_catalog");
 
     if (res.num_tuples() != 1) {
         throw std::runtime_error{
@@ -66,9 +64,9 @@ static void init_database_name(pg_conn_t const &db_connection)
 
 static void init_postgis_version(pg_conn_t const &db_connection)
 {
-    auto const res = db_connection.query(
-        PGRES_TUPLES_OK, "SELECT regexp_split_to_table(extversion, '\\.') FROM"
-                         " pg_extension WHERE extname='postgis'");
+    auto const res = db_connection.exec(
+        "SELECT regexp_split_to_table(extversion, '\\.') FROM"
+        " pg_extension WHERE extname='postgis'");
 
     if (res.num_tuples() == 0) {
         throw std::runtime_error{

src/pgsql-helper.cpp

@@ -84,7 +84,7 @@ bool has_table(pg_conn_t const &db_connection, std::string const &schema,
     auto const sql = "SELECT count(*) FROM pg_tables"
                      "  WHERE schemaname='{}' AND tablename='{}'"_format(
                          schema.empty() ? "public" : schema, table);
-    auto const res = db_connection.query(PGRES_TUPLES_OK, sql);
+    auto const res = db_connection.exec(sql);
     char const *const num = res.get_value(0, 0);
 
     return num[0] == '1' && num[1] == '\0';

src/pgsql.cpp

@@ -37,40 +37,30 @@ char const *pg_conn_t::error_msg() const noexcept
     return PQerrorMessage(m_conn.get());
 }
 
-pg_result_t pg_conn_t::query(ExecStatusType expect, char const *sql) const
+void pg_conn_t::set_config(char const *setting, char const *value) const
+{
+    // Update pg_settings instead of using SET because it does not yield
+    // errors on older versions of PostgreSQL where the settings are not
+    // implemented.
+    exec("UPDATE pg_settings SET setting = '{}' WHERE name = '{}'"_format(
+        value, setting));
+}
+
+pg_result_t pg_conn_t::exec(char const *sql) const
 {
     assert(m_conn);
 
     log_sql("{}", sql);
     pg_result_t res{PQexec(m_conn.get(), sql)};
-    if (res.status() != expect) {
+    if (res.status() != PGRES_COMMAND_OK && res.status() != PGRES_TUPLES_OK) {
         throw std::runtime_error{"Database error: {}"_format(error_msg())};
     }
     return res;
 }
 
-pg_result_t pg_conn_t::query(ExecStatusType expect,
-                             std::string const &sql) const
-{
-    return query(expect, sql.c_str());
-}
-
-void pg_conn_t::set_config(char const *setting, char const *value) const
-{
-    // Update pg_settings instead of using SET because it does not yield
-    // errors on older versions of PostgreSQL where the settings are not
-    // implemented.
-    auto const sql =
-        "UPDATE pg_settings SET setting = '{}' WHERE name = '{}'"_format(
-            value, setting);
-    query(PGRES_TUPLES_OK, sql);
-}
-
-void pg_conn_t::exec(char const *sql) const { query(PGRES_COMMAND_OK, sql); }
-
-void pg_conn_t::exec(std::string const &sql) const
+pg_result_t pg_conn_t::exec(std::string const &sql) const
 {
-    query(PGRES_COMMAND_OK, sql.c_str());
+    return exec(sql.c_str());
 }
 
 void pg_conn_t::copy_start(char const *sql) const

src/pgsql.hpp

@@ -179,6 +179,17 @@ class pg_conn_t
 public:
     explicit pg_conn_t(std::string const &conninfo);
 
+    /**
+     * Run the specified SQL command.
+     *
+     * \param sql The SQL command. If this is empty, nothing is done and a
+     *        default constructed pg_result_t is returned.
+     * \throws std::runtime_exception If the command failed (didn't return
+     *         status code PGRES_COMMAND_OK or PGRES_TUPLES_OK).
+     */
+    pg_result_t exec(char const *sql) const;
+    pg_result_t exec(std::string const &sql) const;
+
     /**
      * Run the named prepared SQL statement and return the results.
      *
@@ -211,32 +222,12 @@ class pg_conn_t
                                       param_ptrs.data());
     }
 
-    /**
-     * Run the specified SQL query and return the results.
-     *
-     * \param expect The expected status code of the SQL command.
-     * \param sql The SQL command.
-     * \throws exception if the result is not as expected.
-     */
-    pg_result_t query(ExecStatusType expect, char const *sql) const;
-    pg_result_t query(ExecStatusType expect, std::string const &sql) const;
-
     /**
      * Update a PostgreSQL setting (like with the SET command). Will silently
      * ignore settings that are not available or any other errors.
      */
     void set_config(char const *setting, char const *value) const;
 
-    /**
-     * Run the specified SQL query. This can only be used for commands that
-     * have no output and return status code PGRES_COMMAND_OK.
-     *
-     * \param sql The SQL command.
-     * \throws exception if the command failed.
-     */
-    void exec(char const *sql) const;
-    void exec(std::string const &sql) 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;

tests/common-pg.hpp

@@ -41,7 +41,7 @@ class conn_t : public pg_conn_t
 
     std::string result_as_string(std::string const &cmd) const
     {
-        pg_result_t const res = query(PGRES_TUPLES_OK, cmd);
+        pg_result_t const res = exec(cmd);
         REQUIRE(res.num_tuples() == 1);
         return std::string{res.get(0, 0)};
     }
@@ -63,14 +63,14 @@ class conn_t : public pg_conn_t
 
     void assert_null(std::string const &cmd) const
     {
-        pg_result_t const res = query(PGRES_TUPLES_OK, cmd);
+        pg_result_t const res = exec(cmd);
         REQUIRE(res.num_tuples() == 1);
         REQUIRE(res.is_null(0, 0));
     }
 
     pg_result_t require_row(std::string const &cmd) const
     {
-        pg_result_t res = query(PGRES_TUPLES_OK, cmd);
+        pg_result_t res = exec(cmd);
         REQUIRE(res.num_tuples() == 1);
 
         return res;

tests/test-db-copy-mgr.cpp

@@ -232,8 +232,7 @@ TEST_CASE("copy_mgr_t")
         mgr.sync();
 
         auto const conn = db.connect();
-        auto const res = conn.query(PGRES_TUPLES_OK,
-                                    "SELECT t FROM test_copy_mgr ORDER BY id");
+        auto const res = conn.exec("SELECT t FROM test_copy_mgr ORDER BY id");
         CHECK(res.num_tuples() == 2);
         CHECK(res.get(0, 0) == "good");
         CHECK(res.get(1, 0) == "better");

tests/test-output-gazetteer.cpp

@@ -260,7 +260,7 @@ class gazetteer_fixture_t
             "SELECT skeys({}), svals({}) FROM place"
             " WHERE osm_type = '{}' AND osm_id = {}"
             " AND class = '{}'"_format(column, column, tchar, id, cls);
-        auto const res = conn.query(PGRES_TUPLES_OK, sql);
+        auto const res = conn.exec(sql);
 
         hstore_list actual;
         for (int i = 0; i < res.num_tuples(); ++i) {

tests/test-pgsql.cpp

@@ -37,7 +37,7 @@ TEST_CASE("Table name with schema")
 TEST_CASE("query with SELECT should work")
 {
     auto conn = db.db().connect();
-    auto const result = conn.query(PGRES_TUPLES_OK, "SELECT 42");
+    auto const result = conn.exec("SELECT 42");
     REQUIRE(result.status() == PGRES_TUPLES_OK);
     REQUIRE(result.num_fields() == 1);
     REQUIRE(result.num_tuples() == 1);
@@ -47,7 +47,7 @@ TEST_CASE("query with SELECT should work")
 TEST_CASE("query with invalid SQL should fail")
 {
     auto conn = db.db().connect();
-    REQUIRE_THROWS(conn.query(PGRES_TUPLES_OK, "NOT-VALID-SQL"));
+    REQUIRE_THROWS(conn.exec("NOT-VALID-SQL"));
 }
 
 TEST_CASE("exec with invalid SQL should fail")