Re: [PATCH v3 04/13] lib: Database version 3: Introduce fine-grained "features"

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+From: David Bremner <david@tethera.net>\r
+To: Austin Clements <amdragon@MIT.EDU>, notmuch@notmuchmail.org\r
+Subject: Re: [PATCH v3 04/13] lib: Database version 3: Introduce fine-grained\r
+       "features"\r
+In-Reply-To: <1406859003-11561-5-git-send-email-amdragon@mit.edu>\r
+References: <1406859003-11561-1-git-send-email-amdragon@mit.edu>\r
+       <1406859003-11561-5-git-send-email-amdragon@mit.edu>\r
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+Date: Sat, 23 Aug 2014 15:21:07 -0700\r
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+\r
+Austin Clements <amdragon@MIT.EDU> writes:\r
+>  \r
+> +    /* Bit mask of features used by this database.  Features are\r
+> +     * named, independent aspects of the database schema.  This is a\r
+> +     * bitwise-OR of NOTMUCH_FEATURE_* values (below). */\r
+> +    unsigned int features;\r
+\r
+Should we be using a fixed size integer (uint_32t or whatever) for\r
+features? iirc the metadata in the database is actually a string, so I\r
+guess arbitrary precision there.\r
+\r
+> +/* Bit masks for _notmuch_database::features. */\r
+> +enum {\r
+> +    /* If set, file names are stored in "file-direntry" terms.  If\r
+> +     * unset, file names are stored in document data.\r
+> +     *\r
+> +     * Introduced: version 1.  Implementation support: both for read;\r
+> +     * required for write. */\r
+> +    NOTMUCH_FEATURE_FILE_TERMS = 1 << 0,\r
+\r
+I agree with Jani that the Implementation support: part is a bit\r
+mystifying without the commit message. Maybe part of the commit message\r
+could migrate here? Or maybe just add a pointer to the comment in database.cc.\r
+\r
+> +            if (! *incompat_out)\r
+\r
+Should we support passing NULL for incompat_out? or at least check for\r
+it?\r
+\r
+> @@ -1048,7 +1164,8 @@ notmuch_database_get_version (notmuch_database_t *notmuch)\r
+>  notmuch_bool_t\r
+>  notmuch_database_needs_upgrade (notmuch_database_t *notmuch)\r
+>  {\r
+> -    return notmuch->needs_upgrade;\r
+> +    return notmuch->mode == NOTMUCH_DATABASE_MODE_READ_WRITE &&\r
+> +    (NOTMUCH_FEATURES_CURRENT & ~notmuch->features);\r
+>  }\r
+\r
+Maybe I'm not thinking hard enough here, but how does this deal with a\r
+feature that is needed to open a database in read only mode? Maybe it\r
+needs a comment for people not as clever as Austin ;).\r
+\r
+d\r
+\r