fixed #582 ALTER percolate index stuck waiting search load; set prefe…

…r writer for RT and percolate indexes

src/searchd.cpp

@@ -838,7 +838,11 @@ void ServedStats_c::CalcStatsForInterval ( const QueryStatContainer_i * pContain
 }
 
 //////////////////////////////////////////////////////////////////////////
-ServedIndex_c::ServedIndex_c ( const ServedDesc_t& tDesc )
+
+// want write lock to wipe out reader and not wait readers
+// but only for RT and PQ indexes as these operations are rare there
+ServedIndex_c::ServedIndex_c ( const ServedDesc_t & tDesc )
+	: m_tLock ( tDesc.m_eType==eITYPE::RT || tDesc.m_eType==eITYPE::PERCOLATE )
 {
 	*(ServedDesc_t*)(this) = tDesc;
 }

src/sphinxstd.h

@@ -3547,6 +3547,11 @@ class RwLock_t : public CSphRwlock
 	{
 		Verify ( Done());
 	}
+
+	explicit RwLock_t ( bool bPreferWriter )
+	{
+		Verify ( Init ( bPreferWriter ) );
+	}
 };