From 93171a5b90f8748790245cff11591064af343863 Mon Sep 17 00:00:00 2001
From: djcb <djcb@djcbsoftware.nl>
Date: Sun, 19 Aug 2012 09:57:49 +0300
Subject: [PATCH] * lib: try to reopen database when it got updated from the
 outside (for guile)

---
 lib/mu-msg-iter.cc | 13 +++++++++++--
 lib/mu-msg-iter.h  |  5 ++++-
 lib/mu-query.cc    | 35 +++++++++++++++++++++++++++++++----
 lib/mu-util.h      |  2 ++
 4 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/lib/mu-msg-iter.cc b/lib/mu-msg-iter.cc
index f6fef8db..3f6ecbc7 100644
--- a/lib/mu-msg-iter.cc
+++ b/lib/mu-msg-iter.cc
@@ -110,9 +110,12 @@ private:
 	MuMsg		*_msg;
 };
 
+
+
 MuMsgIter*
 mu_msg_iter_new (XapianEnquire *enq, size_t maxnum,
-		 gboolean threads, MuMsgFieldId sortfield, gboolean revert)
+		 gboolean threads, MuMsgFieldId sortfield, gboolean revert,
+		 GError **err)
 {
 	g_return_val_if_fail (enq, NULL);
 	/* sortfield should be set to .._NONE when we're not threading */
@@ -125,7 +128,13 @@ mu_msg_iter_new (XapianEnquire *enq, size_t maxnum,
 		return new MuMsgIter ((Xapian::Enquire&)*enq, maxnum, threads,
 				      sortfield, revert ? true : false);
 
-	} MU_XAPIAN_CATCH_BLOCK_RETURN(NULL);
+	} catch (const Xapian::DatabaseModifiedError &dbmex) {
+
+		mu_util_g_set_error (err, MU_ERROR_XAPIAN_MODIFIED,
+				     "database was modified; please reopen");
+		return 0;
+
+	} MU_XAPIAN_CATCH_BLOCK_G_ERROR_RETURN (err, MU_ERROR_XAPIAN, 0);
 }
 
 
diff --git a/lib/mu-msg-iter.h b/lib/mu-msg-iter.h
index 6471a308..d6da9184 100644
--- a/lib/mu-msg-iter.h
+++ b/lib/mu-msg-iter.h
@@ -48,13 +48,16 @@ typedef struct _MuMsgIter MuMsgIter;
  * @param sorting field when using threads; note, when 'threads' is
  * FALSE, this should be MU_MSG_FIELD_ID_NONE
  * @param if TRUE, revert the sorting order
+ * @param err receives error information. if the error is MU_ERROR_XAPIAN_MODIFIED,
+ * the database should be reloaded.
  *
  * @return a new MuMsgIter, or NULL in case of error
  */
 MuMsgIter *mu_msg_iter_new (XapianEnquire *enq,
 			    size_t batchsize, gboolean threads,
 			    MuMsgFieldId threadsortfield,
-			    gboolean revert) G_GNUC_WARN_UNUSED_RESULT;
+			    gboolean revert,
+			    GError **err) G_GNUC_WARN_UNUSED_RESULT;
 
 /**
  * get the next message (which you got from
diff --git a/lib/mu-query.cc b/lib/mu-query.cc
index 10a72fdd..da39a21d 100644
--- a/lib/mu-query.cc
+++ b/lib/mu-query.cc
@@ -309,6 +309,26 @@ mu_query_preprocess (const char *query, GError **err)
 }
 
 
+/* this function is for handling the case where a DatabaseModified
+ * exception is raised. We try to reopen the database, and run the
+ * query again. */
+static MuMsgIter *
+try_requery (MuQuery *self, const char* searchexpr, gboolean threads,
+	     MuMsgFieldId sortfieldid, gboolean revert, int maxnum,
+	     GError **err)
+{
+	try {
+		/* let's assume that infinite regression is
+		 * impossible */
+		self->db().reopen();
+		MU_WRITE_LOG ("reopening db after modification");
+		return mu_query_run (self, searchexpr, threads, sortfieldid,
+				     revert, maxnum, err);
+
+	} MU_XAPIAN_CATCH_BLOCK_G_ERROR_RETURN (err, MU_ERROR_XAPIAN, 0);
+}
+
+
 MuMsgIter*
 mu_query_run (MuQuery *self, const char* searchexpr, gboolean threads,
 	      MuMsgFieldId sortfieldid, gboolean revert, int maxnum,
@@ -320,6 +340,7 @@ mu_query_run (MuQuery *self, const char* searchexpr, gboolean threads,
 			      sortfieldid == MU_MSG_FIELD_ID_NONE,
 			      NULL);
 	try {
+		MuMsgIter *iter;
 		Xapian::Enquire enq (self->db());
 
 		/* note, when our result will be *threaded*, we sort
@@ -336,12 +357,18 @@ mu_query_run (MuQuery *self, const char* searchexpr, gboolean threads,
 
 		enq.set_cutoff(0,0);
 
-		return mu_msg_iter_new (
+		iter = mu_msg_iter_new (
 			reinterpret_cast<XapianEnquire*>(&enq),
 			maxnum <= 0 ? self->db().get_doccount() : maxnum,
-			threads,
-			threads ? sortfieldid : MU_MSG_FIELD_ID_NONE,
-			revert);
+			threads, threads ? sortfieldid : MU_MSG_FIELD_ID_NONE,
+			revert,	err);
+
+		if (err && *err && (*err)->code == MU_ERROR_XAPIAN_MODIFIED) {
+			g_clear_error (err);
+			return try_requery (self, searchexpr, threads, sortfieldid,
+					    revert, maxnum, err);
+		} else
+			return iter;
 
 	} MU_XAPIAN_CATCH_BLOCK_G_ERROR_RETURN (err, MU_ERROR_XAPIAN, 0);
 }
diff --git a/lib/mu-util.h b/lib/mu-util.h
index 7a0b0c40..69cdf9e2 100644
--- a/lib/mu-util.h
+++ b/lib/mu-util.h
@@ -414,6 +414,8 @@ enum _MuError {
 	MU_ERROR_XAPIAN_STORE_FAILED	      = 20,
 	/* could not remove */
 	MU_ERROR_XAPIAN_REMOVE_FAILED	      = 21,
+	/* database was modified; reload */
+	MU_ERROR_XAPIAN_MODIFIED              = 22,
 
 	/* GMime related errors */