From: Timo Sirainen <timo.sirainen@dovecot.fi>
Date: Fri, 18 Nov 2016 13:16:27 +0000 (+0200)
Subject: lib-storage: Add support for storing "mail stubs"
X-Git-Tag: 2.2.27~103
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=66c5edee90c92a4b276ea352dd9a11e41be57c39;p=thirdparty%2Fdovecot%2Fcore.git

lib-storage: Add support for storing "mail stubs"

These allow treating a storage backend as a cache where the mail bodies
don't necessarily exist.
---

diff --git a/src/lib-storage/mail-storage-private.h b/src/lib-storage/mail-storage-private.h
index e5fc1bea81..9874152aa5 100644
--- a/src/lib-storage/mail-storage-private.h
+++ b/src/lib-storage/mail-storage-private.h
@@ -625,7 +625,7 @@ struct mail_save_data {
 	time_t received_date, save_date;
 	int received_tz_offset;
 
-	uint32_t uid;
+	uint32_t uid, stub_seq;
 	char *guid, *pop3_uidl, *from_envelope;
 	unsigned int pop3_order;
 
diff --git a/src/lib-storage/mail-storage.c b/src/lib-storage/mail-storage.c
index e7e790f8ea..d4618205db 100644
--- a/src/lib-storage/mail-storage.c
+++ b/src/lib-storage/mail-storage.c
@@ -1882,6 +1882,9 @@ mailbox_transaction_begin(struct mailbox *box,
 {
 	struct mailbox_transaction_context *trans;
 
+	i_assert((flags & MAILBOX_TRANSACTION_FLAG_FILL_IN_STUB) == 0 ||
+		 (box->flags & MAILBOX_FLAG_USE_STUBS) != 0);
+
 	i_assert(box->opened);
 
 	box->transaction_count++;
@@ -2036,6 +2039,11 @@ void mailbox_save_set_from_envelope(struct mail_save_context *ctx,
 void mailbox_save_set_uid(struct mail_save_context *ctx, uint32_t uid)
 {
 	ctx->data.uid = uid;
+	if ((ctx->transaction->flags & MAILBOX_TRANSACTION_FLAG_FILL_IN_STUB) != 0) {
+		if (!mail_index_lookup_seq(ctx->transaction->view, uid,
+					   &ctx->data.stub_seq) < 0)
+			i_panic("Trying to fill in stub for nonexistent UID %u", uid);
+	}
 }
 
 void mailbox_save_set_guid(struct mail_save_context *ctx, const char *guid)
@@ -2080,6 +2088,11 @@ int mailbox_save_begin(struct mail_save_context **ctx, struct istream *input)
 		return -1;
 	}
 
+	/* if we're filling in a stub, we must have set UID already
+	   (which in turn sets stub_seq) */
+	i_assert(((*ctx)->transaction->flags & MAILBOX_TRANSACTION_FLAG_FILL_IN_STUB) == 0 ||
+		 (*ctx)->data.stub_seq != 0);
+
 	if (!(*ctx)->copying_or_moving) {
 		/* We're actually saving the mail. We're not being called by
 		   mail_storage_copy() because backend didn't support fast
diff --git a/src/lib-storage/mail-storage.h b/src/lib-storage/mail-storage.h
index db089580b7..4ba79cde99 100644
--- a/src/lib-storage/mail-storage.h
+++ b/src/lib-storage/mail-storage.h
@@ -55,7 +55,12 @@ enum mailbox_flags {
 	   inconsistent. For example this disables lazy_expunge plugin and
 	   quota updates (possibly resulting in broken quota). and This is
 	   useful for example when deleting entire user accounts. */
-	MAILBOX_FLAG_DELETE_UNSAFE	= 0x400
+	MAILBOX_FLAG_DELETE_UNSAFE	= 0x400,
+	/* Mailbox is used for caching purposes. Some of the mails may be
+	   stubs, which exist in the index but that don't have a mail body.
+	   The backend shouldn't treat it as corruption if a mail body isn't
+	   found. */
+	MAILBOX_FLAG_USE_STUBS		= 0x800,
 };
 
 enum mailbox_feature {
@@ -189,7 +194,11 @@ enum mailbox_transaction_flags {
 	/* Don't trigger any notifications for this transaction. This
 	   especially means the notify plugin. This would normally be used only
 	   with _FLAG_SYNC. */
-	MAILBOX_TRANSACTION_FLAG_NO_NOTIFY	= 0x40
+	MAILBOX_TRANSACTION_FLAG_NO_NOTIFY	= 0x40,
+	/* Append fills in an existing stub mail for the specified UID,
+	   instead of saving a new mail. This requires mailbox to be opened
+	   with MAILBOX_FLAG_USE_STUBS. */
+	MAILBOX_TRANSACTION_FLAG_FILL_IN_STUB	= 0x80,
 };
 
 enum mailbox_sync_flags {