[PATCH 1/4] Use the Xapian::DB_RETRY_LOCK flag when available

[David Bremner <david@tethera.net>]

From: Istvan Marko <notmuch@kismala.com>

Xapian 1.3 has introduced the DB_RETRY_LOCK flag (Xapian bug
275). Detect it in configure and use it if available. With this flag
commands that need the write lock will wait for their turn instead of
aborting when it's not immediately available.
---
 configure       | 20 ++++++++++++++++++++
 lib/database.cc |  8 +++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index ce1d698..e9de9c6 100755
--- a/configure
+++ b/configure
@@ -392,6 +392,22 @@ EOF
     rm -f _field_processor.o _field_processor.cc
 
     default_xapian_backend=""
+    # DB_RETRY_LOCK is only supported on Xapian > 1.3.2
+    have_xapian_db_retry_lock=0
+    printf "Checking for Xapian lock retry support... "
+    cat>_retry.cc<<EOF
+#include <xapian.h>
+int flag = Xapian::DB_RETRY_LOCK;
+EOF
+    if ${CXX} ${CXXFLAGS_for_sh} ${xapian_cxxflags} -c _retry.cc -o _retry.o > /dev/null 2>&1
+    then
+	have_xapian_db_retry_lock=1
+	printf "Yes.\n"
+    else
+	printf "No. (optional)\n"
+    fi
+    rm -f _retry.o _retry.cc
+
     printf "Testing default Xapian backend... "
     cat >_default_backend.cc <<EOF
 #include <xapian.h>
@@ -1022,6 +1038,9 @@ HAVE_XAPIAN_COMPACT = ${have_xapian_compact}
 # Whether the Xapian version in use supports field processors
 HAVE_XAPIAN_FIELD_PROCESSOR = ${have_xapian_field_processor}
 
+# Whether the Xapian version in use supports DB_RETRY_LOCK
+HAVE_XAPIAN_DB_RETRY_LOCK = ${have_xapian_db_retry_lock}
+
 # Whether the getpwuid_r function is standards-compliant
 # (if not, then notmuch will #define _POSIX_PTHREAD_SEMANTICS
 # to enable the standards-compliant version -- needed for Solaris)
@@ -1097,6 +1116,7 @@ COMMON_CONFIGURE_CFLAGS = \\
 	-DSTD_ASCTIME=\$(STD_ASCTIME)				\\
 	-DHAVE_XAPIAN_COMPACT=\$(HAVE_XAPIAN_COMPACT)		\\
 	-DHAVE_XAPIAN_FIELD_PROCESSOR=\$(HAVE_XAPIAN_FIELD_PROCESSOR) \\
+	-DHAVE_XAPIAN_DB_RETRY_LOCK=\$(HAVE_XAPIAN_DB_RETRY_LOCK) \\
 	-DUTIL_BYTE_ORDER=\$(UTIL_BYTE_ORDER)
 
 CONFIGURE_CFLAGS = \$(COMMON_CONFIGURE_CFLAGS)
diff --git a/lib/database.cc b/lib/database.cc
index 9630000..e4f3ab5 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -49,6 +49,12 @@ typedef struct {
 #define STRINGIFY(s) _SUB_STRINGIFY(s)
 #define _SUB_STRINGIFY(s) #s
 
+#if HAVE_XAPIAN_DB_RETRY_LOCK
+#define DB_ACTION (Xapian::DB_CREATE_OR_OPEN | Xapian::DB_RETRY_LOCK)
+#else
+#define DB_ACTION Xapian::DB_CREATE_OR_OPEN
+#endif
+
 /* Here's the current schema for our database (for NOTMUCH_DATABASE_VERSION):
  *
  * We currently have three different types of documents (mail, ghost,
@@ -931,7 +937,7 @@ notmuch_database_open_verbose (const char *path,
 
 	if (mode == NOTMUCH_DATABASE_MODE_READ_WRITE) {
 	    notmuch->xapian_db = new Xapian::WritableDatabase (xapian_path,
-							       Xapian::DB_CREATE_OR_OPEN);
+							       DB_ACTION);
 	} else {
 	    notmuch->xapian_db = new Xapian::Database (xapian_path);
 	}
-- 
2.8.1