[tracker/sam/README: 1/5] Add TRACKER_DEBUG environment variable, use for SQL debug

[Sam Thursfield <sthursfield src gnome org>]

commit 01dd1f88777fc1875c12b119965f8a4481ca6b6a
Author: Sam Thursfield <sam afuera me uk>
Date:   Mon Apr 20 00:29:47 2020 +0200

    Add TRACKER_DEBUG environment variable, use for SQL debug
    
    This works the same as GTK's GTK_DEBUG variable. It will
    allow us to include more types of optional debugging info,
    and will make the default debug output more readlable.
    
    See https://gitlab.gnome.org/GNOME/tracker/issues/178

 .gitlab-ci.yml                                    |  1 +
 HACKING.md                                        |  2 +
 meson.build                                       | 13 ++++++
 src/libtracker-common/meson.build                 |  1 +
 src/libtracker-common/tracker-common.h            |  1 +
 src/libtracker-common/tracker-debug.c             | 57 +++++++++++++++++++++++
 src/libtracker-common/tracker-debug.h             | 54 +++++++++++++++++++++
 src/libtracker-data/tracker-db-interface-sqlite.c |  3 +-
 8 files changed, 131 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8c62a82ad..a2375a1f1 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -37,6 +37,7 @@ stages:
       echo
       echo "Test suite settings:"
       echo
+      echo "TRACKER_DEBUG: ${TRACKER_DEBUG}"
       echo "TRACKER_VERBOSITY: ${TRACKER_VERBOSITY}"
       echo "TRACKER_TESTS_VERBOSE: ${TRACKER_TESTS_VERBOSE}"
       echo "MESON_TEST_EXTRA_ARGS: ${MESON_TEST_EXTRA_ARGS}"
diff --git a/HACKING.md b/HACKING.md
index f90522a50..671d48195 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -31,6 +31,8 @@ OpenSuSE do automated whole-system testing that includes the GNOME desktop for t
 
 The following environment variables control logging from Tracker daemons:
 
+  * `TRACKER_DEBUG`: takes a comma-separated list of keywords to enable
+    extra debugging output. Use the keyword 'help' for a list of keywords.
   * `TRACKER_VERBOSITY`: takes a value of 1, 2 or 3 and causes increasing
     amounts of log output from Tracker code to be written to stdout.
   * `G_MESSAGES_DEBUG`: controls log output from GLib-based libraries that
diff --git a/meson.build b/meson.build
index 407ff80a5..99a1077ef 100644
--- a/meson.build
+++ b/meson.build
@@ -72,6 +72,19 @@ add_project_arguments(['-D', 'TRACKER_COMPILATION'],
                       ['-D', 'G_LOG_DOMAIN="Tracker"'],
                       language: 'vala')
 
+debug_cflags = []
+buildtype = get_option('buildtype')
+if buildtype.startswith('debug')
+  debug_cflags += '-DG_ENABLE_DEBUG'
+  if buildtype == 'debug'
+    debug_cflags += '-DG_ENABLE_CONSISTENCY_CHECKS'
+  endif
+elif buildtype == 'release'
+  debug_cflags += '-DG_DISABLE_CAST_CHECKS'
+endif
+
+add_project_arguments(debug_cflags, language: 'c')
+
 ##################################################################
 # Check for libtracker-common, make sure libstemmer exists
 ##################################################################
diff --git a/src/libtracker-common/meson.build b/src/libtracker-common/meson.build
index 3ec6caec0..11e610d09 100644
--- a/src/libtracker-common/meson.build
+++ b/src/libtracker-common/meson.build
@@ -12,6 +12,7 @@ tracker_common_enum_header = enums[1]
 
 tracker_common_sources = [
   'tracker-date-time.c',
+  'tracker-debug.c',
   'tracker-file-utils.c',
   'tracker-log.c',
   'tracker-type-utils.c',
diff --git a/src/libtracker-common/tracker-common.h b/src/libtracker-common/tracker-common.h
index 8d5df2be9..0a9267ed9 100644
--- a/src/libtracker-common/tracker-common.h
+++ b/src/libtracker-common/tracker-common.h
@@ -29,6 +29,7 @@
 #define __LIBTRACKER_COMMON_INSIDE__
 
 #include "tracker-date-time.h"
+#include "tracker-debug.h"
 #include "tracker-file-utils.h"
 #include "tracker-language.h"
 #include "tracker-log.h"
diff --git a/src/libtracker-common/tracker-debug.c b/src/libtracker-common/tracker-debug.c
new file mode 100644
index 000000000..75b8d2840
--- /dev/null
+++ b/src/libtracker-common/tracker-debug.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2020, Sam Thursfield <sam afuera me uk>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.          See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ */
+
+#include "config.h"
+
+#include "tracker-debug.h"
+
+#ifdef G_ENABLE_DEBUG
+static const GDebugKey tracker_debug_keys[] = {
+  { "sql-statements", TRACKER_DEBUG_SQL_STATEMENTS },
+};
+#endif /* G_ENABLE_DEBUG */
+
+static gpointer
+parse_debug_flags ()
+{
+       const gchar *env_string;
+       guint flags;
+
+       env_string = g_getenv ("TRACKER_DEBUG");
+       if (env_string != NULL) {
+#ifdef G_ENABLE_DEBUG
+               flags = g_parse_debug_string (env_string, tracker_debug_keys, G_N_ELEMENTS 
(tracker_debug_keys));
+#else
+               g_warning ("TRACKER_DEBUG set but ignored because tracker isn't built with G_ENABLE_DEBUG");
+#endif  /* G_ENABLE_DEBUG */
+               env_string = NULL;
+       }
+
+       return GINT_TO_POINTER (flags);
+}
+
+guint
+tracker_get_debug_flags (void)
+{
+       static GOnce once = G_ONCE_INIT;
+
+       g_once (&once, parse_debug_flags, NULL);
+
+       return GPOINTER_TO_INT (once.retval);
+}
diff --git a/src/libtracker-common/tracker-debug.h b/src/libtracker-common/tracker-debug.h
new file mode 100644
index 000000000..aaca4fc07
--- /dev/null
+++ b/src/libtracker-common/tracker-debug.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2020, Sam Thursfield <sam afuera me uk>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ */
+
+#ifndef __TRACKER_DEBUG_H__
+#define __TRACKER_DEBUG_H__
+
+#if !defined (__LIBTRACKER_COMMON_INSIDE__) && !defined (TRACKER_COMPILATION)
+#error "only <libtracker-common/tracker-common.h> must be included directly."
+#endif
+
+#include <glib.h>
+
+G_BEGIN_DECLS
+
+typedef enum {
+  TRACKER_DEBUG_SQL_STATEMENTS  = 1 <<  1,
+} TrackerDebugFlag;
+
+#ifdef G_ENABLE_DEBUG
+
+#define TRACKER_DEBUG_CHECK(type) G_UNLIKELY (tracker_get_debug_flags () & TRACKER_DEBUG_##type)
+
+#define TRACKER_NOTE(type,action)                G_STMT_START {     \
+    if (TRACKER_DEBUG_CHECK (type))                                 \
+       { action; };                              } G_STMT_END
+
+#else /* !G_ENABLE_DEBUG */
+
+#define TRACKER_DEBUG_CHECK(type) 0
+#define TRACKER_NOTE(type, action)
+
+#endif /* G_ENABLE_DEBUG */
+
+guint tracker_get_debug_flags (void);
+
+G_END_DECLS
+
+#endif /* __TRACKER_DEBUG_H__ */
diff --git a/src/libtracker-data/tracker-db-interface-sqlite.c 
b/src/libtracker-data/tracker-db-interface-sqlite.c
index fb5bcb46d..545f26690 100644
--- a/src/libtracker-data/tracker-db-interface-sqlite.c
+++ b/src/libtracker-data/tracker-db-interface-sqlite.c
@@ -27,6 +27,7 @@
 #include <errno.h>
 
 #include <libtracker-common/tracker-date-time.h>
+#include <libtracker-common/tracker-debug.h>
 #include <libtracker-common/tracker-locale.h>
 #include <libtracker-common/tracker-parser.h>
 
@@ -2512,7 +2513,7 @@ tracker_db_interface_prepare_stmt (TrackerDBInterface  *db_interface,
        sqlite3_stmt *sqlite_stmt;
        int retval;
 
-       g_debug ("Preparing query: '%s'", full_query);
+       TRACKER_NOTE (SQL_STATEMENTS, g_message ("Preparing query: '%s'", full_query));
        retval = sqlite3_prepare_v2 (db_interface->db, full_query, -1, &sqlite_stmt, NULL);
 
        if (retval != SQLITE_OK) {