diff --git a/src/mu-msg-fields.c b/src/mu-msg-fields.c
index 714d57eb..d76e0937 100644
--- a/src/mu-msg-fields.c
+++ b/src/mu-msg-fields.c
@@ -29,21 +29,22 @@
  * must be in the value (at least when using MuMsgIter)
  */
 enum _FieldFlags { 
-	FLAG_GMIME	      = 1 << 0,	/* field retrieved through
-					 * gmime */
-	FLAG_XAPIAN_INDEX     = 1 << 1,	/* field is indexed in
-					 * xapian */
-	FLAG_XAPIAN_TERM      = 1 << 2,	/* field stored as term in
-					 * xapian */
-	FLAG_XAPIAN_VALUE     = 1 << 3,	/* field stored as value in
-					 * xapian */
-	FLAG_XAPIAN_CONTACT   = 1 << 4,	/* field contains one or more
-					 * e-mail-addresses */
-	FLAG_XAPIAN_ESCAPE    = 1 << 5, /* field needs escaping for
-					 * xapian */
-	FLAG_NORMALIZE	      = 1 << 6  /* field needs flattening for
-					 * case/accents */
-
+		FLAG_GMIME	           = 1 << 0, /* field retrieved through
+										  * gmime */
+		FLAG_XAPIAN_INDEX     = 1 << 1,	/* field is indexed in
+										 * xapian */
+		FLAG_XAPIAN_TERM      = 1 << 2,	/* field stored as term in
+										 * xapian */
+		FLAG_XAPIAN_VALUE     = 1 << 3,	/* field stored as value in
+										 * xapian */
+		FLAG_XAPIAN_CONTACT   = 1 << 4,	/* field contains one or more
+										 * e-mail-addresses */
+		FLAG_XAPIAN_ESCAPE    = 1 << 5, /* field needs escaping for
+										 * xapian */
+		FLAG_NORMALIZE	      = 1 << 6, /* field needs flattening for
+										 * case/accents */
+		FLAG_DONT_CACHE       = 1 << 7  /* don't cache this field in
+										  * the MuMsg cache */
 };
 typedef enum _FieldFlags	FieldFlags;
 
@@ -51,14 +52,14 @@ typedef enum _FieldFlags	FieldFlags;
  * this struct describes the fields of an e-mail
  /*/
 struct _MuMsgField {
-	MuMsgFieldId    _id;		/* the id of the field */
-	MuMsgFieldType  _type;		/* the type of the field */
-	const char     *_name;		/* the name of the field */
-	const char     _shortcut;	/* the shortcut for use in
-					 * --fields and sorting */
-	const char     _xprefix;	/* the Xapian-prefix  */ 
-	FieldFlags      _flags;		/* the flags that tells us
-					 * what to do */
+		MuMsgFieldId    _id;		/* the id of the field */
+		MuMsgFieldType  _type;		/* the type of the field */
+		const char     *_name;		/* the name of the field */
+		const char     _shortcut;	/* the shortcut for use in
+									 * --fields and sorting */
+		const char     _xprefix;	/* the Xapian-prefix  */ 
+		FieldFlags      _flags;		/* the flags that tells us
+									 * what to do */
 };
 typedef struct _MuMsgField MuMsgField;
 
@@ -67,127 +68,121 @@ typedef struct _MuMsgField MuMsgField;
  * lowercase */
 static const MuMsgField FIELD_DATA[] = {
 
-	{  
-		MU_MSG_FIELD_ID_BCC,
-		MU_MSG_FIELD_TYPE_STRING,
-		"bcc" , 'h', 'H',  /* 'hidden */
-		FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
-	},
+		{  
+				MU_MSG_FIELD_ID_BCC,
+				MU_MSG_FIELD_TYPE_STRING,
+				"bcc" , 'h', 'H',  /* 'hidden */
+				FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
+		},
 	
-	{  
-		MU_MSG_FIELD_ID_BODY_TEXT,
-		MU_MSG_FIELD_TYPE_STRING,
-		"body", 'b', 'B',
-		FLAG_GMIME | FLAG_XAPIAN_INDEX | FLAG_NORMALIZE
-	},
+		{  
+				MU_MSG_FIELD_ID_BODY_TEXT,
+				MU_MSG_FIELD_TYPE_STRING,
+				"body", 'b', 'B',
+				FLAG_GMIME | FLAG_XAPIAN_INDEX | FLAG_NORMALIZE |
+				FLAG_DONT_CACHE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_BODY_HTML,
-		MU_MSG_FIELD_TYPE_STRING,
-		"bodyhtml", 'h', 0,
-		FLAG_GMIME
-	},
+		{ 
+				MU_MSG_FIELD_ID_BODY_HTML,
+				MU_MSG_FIELD_TYPE_STRING,
+				"bodyhtml", 'h', 0,
+				FLAG_GMIME | FLAG_DONT_CACHE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_CC,
-		MU_MSG_FIELD_TYPE_STRING,
-		"cc", 'c', 'C',
-		FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_CC,
+				MU_MSG_FIELD_TYPE_STRING,
+				"cc", 'c', 'C',
+				FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_DATE, 
-		MU_MSG_FIELD_TYPE_TIME_T,
-		"date", 'd', 'D',
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_DATE, 
+				MU_MSG_FIELD_TYPE_TIME_T,
+				"date", 'd', 'D',
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_FLAGS, 
-		MU_MSG_FIELD_TYPE_INT,
-		"flag", 'g', 'G',  /* flaGs */
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_FLAGS, 
+				MU_MSG_FIELD_TYPE_INT,
+				"flag", 'g', 'G',  /* flaGs */
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
+		},
 
-	{ 
-		MU_MSG_FIELD_ID_FROM,
-		MU_MSG_FIELD_TYPE_STRING,
-		"from", 'f', 'F',
-		FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_FROM,
+				MU_MSG_FIELD_TYPE_STRING,
+				"from", 'f', 'F',
+				FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE
+		},
 
-	{   
-		MU_MSG_FIELD_ID_PATH, 
-		MU_MSG_FIELD_TYPE_STRING,
-		"path", 'l', 'L',   /* 'l' for location */
- 		FLAG_GMIME | FLAG_XAPIAN_VALUE
-	},
+		{   
+				MU_MSG_FIELD_ID_PATH, 
+				MU_MSG_FIELD_TYPE_STRING,
+				"path", 'l', 'L',   /* 'l' for location */
+				FLAG_GMIME | FLAG_XAPIAN_VALUE
+		},
 
-	{   
-		MU_MSG_FIELD_ID_MAILDIR, 
-		MU_MSG_FIELD_TYPE_STRING,
-		"maildir", 'm', 'M',
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE |
-		FLAG_NORMALIZE | FLAG_XAPIAN_ESCAPE
-	},
+		{   
+				MU_MSG_FIELD_ID_MAILDIR, 
+				MU_MSG_FIELD_TYPE_STRING,
+				"maildir", 'm', 'M',
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE |
+				FLAG_NORMALIZE | FLAG_XAPIAN_ESCAPE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_PRIO,
-		MU_MSG_FIELD_TYPE_INT,
-		"prio", 'p', 'P',  
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_PRIO,
+				MU_MSG_FIELD_TYPE_INT,
+				"prio", 'p', 'P',  
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
+		},
 
-	{ 
-		MU_MSG_FIELD_ID_SIZE,
-		MU_MSG_FIELD_TYPE_BYTESIZE,
-		"size", 'z', 'Z', /* siZe */
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
-	},
+		{ 
+				MU_MSG_FIELD_ID_SIZE,
+				MU_MSG_FIELD_TYPE_BYTESIZE,
+				"size", 'z', 'Z', /* siZe */
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_SUBJECT,
-		MU_MSG_FIELD_TYPE_STRING,
-		"subject", 's', 'S',
-		FLAG_GMIME | FLAG_XAPIAN_INDEX | FLAG_XAPIAN_VALUE |
-		FLAG_NORMALIZE
-	},
+		{ 
+				MU_MSG_FIELD_ID_SUBJECT,
+				MU_MSG_FIELD_TYPE_STRING,
+				"subject", 's', 'S',
+				FLAG_GMIME | FLAG_XAPIAN_INDEX | FLAG_XAPIAN_VALUE |
+				FLAG_NORMALIZE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_TO,
-		MU_MSG_FIELD_TYPE_STRING,
-		"to", 't', 'T',
-		FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE 
-	},
+		{ 
+				MU_MSG_FIELD_ID_TO,
+				MU_MSG_FIELD_TYPE_STRING,
+				"to", 't', 'T',
+				FLAG_GMIME | FLAG_XAPIAN_CONTACT | FLAG_XAPIAN_VALUE 
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_MSGID,
-		MU_MSG_FIELD_TYPE_STRING,
-		"msgid", 'i', 'I',  /* 'i' for Id */
-		FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE |
-		FLAG_XAPIAN_ESCAPE
-	},
+		{ 
+				MU_MSG_FIELD_ID_MSGID,
+				MU_MSG_FIELD_TYPE_STRING,
+				"msgid", 'i', 'I',  /* 'i' for Id */
+				FLAG_GMIME | FLAG_XAPIAN_TERM | FLAG_XAPIAN_VALUE |
+				FLAG_XAPIAN_ESCAPE
+		},
 	
-	{ 
-		MU_MSG_FIELD_ID_TIMESTAMP,
-		MU_MSG_FIELD_TYPE_TIME_T,
-		"timestamp", 'x', 0,
-		FLAG_GMIME 
-	},
+		{ 
+				MU_MSG_FIELD_ID_TIMESTAMP,
+				MU_MSG_FIELD_TYPE_TIME_T,
+				"timestamp", 'x', 0,
+				FLAG_GMIME 
+		},
 
-	{ 
-		MU_MSG_FIELD_ID_REFS,
-		MU_MSG_FIELD_TYPE_STRING,
-		"refs", 'r', 'R',
-		FLAG_GMIME | FLAG_XAPIAN_VALUE
-	},
-
-	{ 
-		MU_MSG_FIELD_ID_SUMMARY,
-		MU_MSG_FIELD_TYPE_STRING,
-		NULL, 0, 0,
-		FLAG_GMIME
-	}
+		{ 
+				MU_MSG_FIELD_ID_REFS,
+				MU_MSG_FIELD_TYPE_STRING,
+				"refs", 'r', 'R',
+				FLAG_GMIME | FLAG_XAPIAN_VALUE
+		}
 };
 
 /* the MsgField data in an array, indexed by the MsgFieldId;
@@ -196,149 +191,158 @@ static const MuMsgField FIELD_DATA[] = {
 static MuMsgField* _msg_field_data[MU_MSG_FIELD_ID_NUM];
 static const MuMsgField* mu_msg_field (MuMsgFieldId id)
 {
-	static gboolean _initialized = FALSE;
+		static gboolean _initialized = FALSE;
 
-	/* initialize the array, but only once... */
-	if (G_UNLIKELY(!_initialized)) {
-		int i; 
-		for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
-			_msg_field_data[FIELD_DATA[i]._id] =
-				(MuMsgField*)&FIELD_DATA[i];
-		_initialized = TRUE;
-	}
+		/* initialize the array, but only once... */
+		if (G_UNLIKELY(!_initialized)) {
+				int i; 
+				for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
+						_msg_field_data[FIELD_DATA[i]._id] =
+								(MuMsgField*)&FIELD_DATA[i];
+				_initialized = TRUE;
+		}
 
-	return _msg_field_data[id];
+		return _msg_field_data[id];
 }
 
 
 void
 mu_msg_field_foreach (MuMsgFieldForEachFunc func, gconstpointer data)
 {
-	int i;
-	for (i = 0; i != MU_MSG_FIELD_ID_NUM; ++i)
-		func (i, data);
+		int i;
+		for (i = 0; i != MU_MSG_FIELD_ID_NUM; ++i)
+				func (i, data);
 }
 
 
 MuMsgFieldId
 mu_msg_field_id_from_name (const char* str, gboolean err)
 {
- 	int i;
+		int i;
 
-	g_return_val_if_fail (str, MU_MSG_FIELD_ID_NONE);
+		g_return_val_if_fail (str, MU_MSG_FIELD_ID_NONE);
 	
-	for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
-		if (g_strcmp0(str, FIELD_DATA[i]._name) == 0)
-			return FIELD_DATA[i]._id;
+		for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
+				if (g_strcmp0(str, FIELD_DATA[i]._name) == 0)
+						return FIELD_DATA[i]._id;
 
-	if (err)
-		g_return_val_if_reached (MU_MSG_FIELD_ID_NONE);
+		if (err)
+				g_return_val_if_reached (MU_MSG_FIELD_ID_NONE);
 
-	return MU_MSG_FIELD_ID_NONE;
+		return MU_MSG_FIELD_ID_NONE;
 }
 
 
 MuMsgFieldId
 mu_msg_field_id_from_shortcut (char kar, gboolean err)
 {
- 	int i;
-	for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
-		if (kar == FIELD_DATA[i]._shortcut)
-			return FIELD_DATA[i]._id;
+		int i;
+		for (i = 0; i != G_N_ELEMENTS(FIELD_DATA); ++i)
+				if (kar == FIELD_DATA[i]._shortcut)
+						return FIELD_DATA[i]._id;
 
-	if (err)
-		g_return_val_if_reached (MU_MSG_FIELD_ID_NONE);
+		if (err)
+				g_return_val_if_reached (MU_MSG_FIELD_ID_NONE);
 
-	return MU_MSG_FIELD_ID_NONE;
+		return MU_MSG_FIELD_ID_NONE;
 }
 
 
 gboolean
 mu_msg_field_gmime (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_GMIME;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_GMIME;
 }
 
 
 gboolean
 mu_msg_field_xapian_index  (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_XAPIAN_INDEX;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_XAPIAN_INDEX;
 }
 
 gboolean
 mu_msg_field_xapian_value (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_XAPIAN_VALUE;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_XAPIAN_VALUE;
 }
 
 gboolean
 mu_msg_field_xapian_term (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_XAPIAN_TERM;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_XAPIAN_TERM;
+}
+
+
+
+gboolean
+mu_msg_field_is_cacheable (MuMsgFieldId id)
+{
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_DONT_CACHE ? FALSE : TRUE;
 }
 
 gboolean
 mu_msg_field_xapian_contact (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_XAPIAN_CONTACT;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_XAPIAN_CONTACT;
 }
 
 
 gboolean
 mu_msg_field_normalize (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_NORMALIZE;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_NORMALIZE;
 }
 
 gboolean
 mu_msg_field_xapian_escape (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
-	return mu_msg_field(id)->_flags & FLAG_XAPIAN_ESCAPE;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),FALSE);
+		return mu_msg_field(id)->_flags & FLAG_XAPIAN_ESCAPE;
 }
 
 
 gboolean
 mu_msg_field_is_numeric (MuMsgFieldId mfid)
 {
-	MuMsgFieldType type;
+		MuMsgFieldType type;
 	
-	g_return_val_if_fail (mu_msg_field_id_is_valid(mfid),FALSE);
+		g_return_val_if_fail (mu_msg_field_id_is_valid(mfid),FALSE);
 
-	type = mu_msg_field_type (mfid);
+		type = mu_msg_field_type (mfid);
 	
-	return  type == MU_MSG_FIELD_TYPE_BYTESIZE ||
-		type == MU_MSG_FIELD_TYPE_TIME_T ||
-		type == MU_MSG_FIELD_TYPE_INT;
+		return  type == MU_MSG_FIELD_TYPE_BYTESIZE ||
+				type == MU_MSG_FIELD_TYPE_TIME_T ||
+				type == MU_MSG_FIELD_TYPE_INT;
 }
 
 const char*    
 mu_msg_field_name (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),NULL);
-	return mu_msg_field(id)->_name;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),NULL);
+		return mu_msg_field(id)->_name;
 }
 
 char
 mu_msg_field_shortcut (MuMsgFieldId id)
 {	
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),0);
-	return mu_msg_field(id)->_shortcut;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),0);
+		return mu_msg_field(id)->_shortcut;
 }
 
 
 char
 mu_msg_field_xapian_prefix (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),0);
-	return mu_msg_field(id)->_xprefix;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),0);
+		return mu_msg_field(id)->_xprefix;
 }
 
 
@@ -347,7 +351,7 @@ mu_msg_field_xapian_prefix (MuMsgFieldId id)
 MuMsgFieldType 
 mu_msg_field_type (MuMsgFieldId id)
 {
-	g_return_val_if_fail (mu_msg_field_id_is_valid(id),
-			      MU_MSG_FIELD_TYPE_NONE);
-	return mu_msg_field(id)->_type;
+		g_return_val_if_fail (mu_msg_field_id_is_valid(id),
+							  MU_MSG_FIELD_TYPE_NONE);
+		return mu_msg_field(id)->_type;
 }
diff --git a/src/mu-msg-fields.h b/src/mu-msg-fields.h
index 84fc4f5f..0f7949e5 100644
--- a/src/mu-msg-fields.h
+++ b/src/mu-msg-fields.h
@@ -27,24 +27,27 @@ G_BEGIN_DECLS
 /* don't change the order, add new types at the end, as these numbers
  * are used in the database */
 enum _MuMsgFieldId {
-	
+
+	/* first all the string-based ones */
 	MU_MSG_FIELD_ID_BCC         = 0,
- 	MU_MSG_FIELD_ID_BODY_TEXT,
 	MU_MSG_FIELD_ID_BODY_HTML,
+	MU_MSG_FIELD_ID_BODY_TEXT,
 	MU_MSG_FIELD_ID_CC,
-	MU_MSG_FIELD_ID_DATE,
-	MU_MSG_FIELD_ID_FLAGS,
 	MU_MSG_FIELD_ID_FROM,
+	MU_MSG_FIELD_ID_MAILDIR,
+	MU_MSG_FIELD_ID_MSGID,
 	MU_MSG_FIELD_ID_PATH,
-	MU_MSG_FIELD_ID_MAILDIR, 
-	MU_MSG_FIELD_ID_PRIO,
-	MU_MSG_FIELD_ID_SIZE,
+	MU_MSG_FIELD_ID_REFS,
 	MU_MSG_FIELD_ID_SUBJECT,
 	MU_MSG_FIELD_ID_TO,
-	MU_MSG_FIELD_ID_MSGID,
+	/* MU_MSG_STRING_FIELD_ID_NUM, see below */
+
+	/* then the numerical ones */
+	MU_MSG_FIELD_ID_DATE,
+	MU_MSG_FIELD_ID_FLAGS,
+	MU_MSG_FIELD_ID_PRIO,
+	MU_MSG_FIELD_ID_SIZE,
 	MU_MSG_FIELD_ID_TIMESTAMP,
-	MU_MSG_FIELD_ID_REFS,
-	MU_MSG_FIELD_ID_SUMMARY,
 	
 	MU_MSG_FIELD_ID_NUM,
 
@@ -57,6 +60,8 @@ typedef enum _MuMsgFieldId MuMsgFieldId;
 
 /* some specials... */
 static const MuMsgFieldId MU_MSG_FIELD_ID_NONE = (MuMsgFieldId)-1;
+#define MU_MSG_STRING_FIELD_ID_NUM (MU_MSG_FIELD_ID_TO + 1)
+
 
 #define mu_msg_field_id_is_valid(MFID) \
 	((MFID) < MU_MSG_FIELD_ID_NUM)
@@ -149,6 +154,16 @@ MuMsgFieldType mu_msg_field_type (MuMsgFieldId id) G_GNUC_PURE;
 gboolean mu_msg_field_is_numeric (MuMsgFieldId id) G_GNUC_PURE;
 
 
+/**
+ * whether the field value should be cached (in MuMsg) -- we cache
+ * values so we can use the MuMsg without needing to keep the
+ * underlying data source (the GMimeMessage or the database ptr) alive
+ * in practice, the fields we *don't* cache are the message body
+ * (html, txt), because they take too much memory
+ */
+gboolean mu_msg_field_is_cacheable (MuMsgFieldId id) G_GNUC_PURE;
+
+
 /**
  * is the field Xapian-indexable? That is, should this field be
  * indexed in the in the Xapian database, so we can use the all the