Format 20 upgrade to NODES

I'd like to enable NODES as a replacement for BASE_NODE and
WORKING_NODE. This would involve bumping the format number, and old
working copies would get automatically upgraded.

This is not the final NODES data model. It currently just uses
NODES.op_depth as 0 or 2 to indicate the equivalent of BASE_NODE and
WORKING_NODE. Another wc upgrade will be required in the future to
enable full op_depth behaviour.

The advantages of the proposed upgrade include: dropping the
conditional code, having everyone exercise the new code.

The disadvantages include: a wc upgrade, the testsuite is slightly
(maybe 2% on my machine) slower.

If you build the current format 19 with SVN_WC__NODES then both NODES
and BASE_NODE/WORKING_NODE tables are created. DB writes modify both
NODES and BASE/WORKING and DB reads check that the same data is
obtained from NODES and BASE/WORKING. The regression tests pass like
this so we have confidence that NODES is an adequate replacement for
BASE/WORKING.

If you build format 19 with both SVN_WC__NODES and SVN_WC__NODES_ONLY
then only the NODES table is written and read, BASE/WORKING remain
empty. The upgrade would be using this code, but would also enable
the upgrade and dropping of the BASE/WORKING tables. The change would
be the patch below:

* subversion/libsvn_wc/wc.h
  (SVN_WC__VERSION): Bump to 20.

* subversion/libsvn_wc/wc.h
  (STMT_UPGRADE_TO_20): Renamed from DISABLED_STMT_UPGRADE_TO_20 and
   enabled, drop the "inherited" BASE_NODE format 99 stuff.
   

Index: subversion/libsvn_wc/wc.h
===================================================================
--- subversion/libsvn_wc/wc.h (revision 1004712)
+++ subversion/libsvn_wc/wc.h (working copy)
@@ -129,7 +129,7 @@
  * Please document any further format changes here.
  */
 
-#define SVN_WC__VERSION 19
+#define SVN_WC__VERSION 20
 
 /* Formats <= this have no concept of "revert text-base/props". */
 #define SVN_WC__NO_REVERT_FILES 4
Index: subversion/libsvn_wc/wc-metadata.sql
===================================================================
--- subversion/libsvn_wc/wc-metadata.sql (revision 1004712)
+++ subversion/libsvn_wc/wc-metadata.sql (working copy)
@@ -987,10 +987,8 @@
 
 /* Format 20 introduces NODES and removes BASE_NODE and WORKING_NODE */
 
-/* ### Enable this bit and take out the BASE_NODE stuff in format 99 below.
+-- STMT_UPGRADE_TO_20
 
--- DISABLED_STMT_UPGRADE_TO_20
-
 INSERT INTO NODES
 SELECT wc_id, local_relpath, 0 AS op_depth, parent_relpath,
        repos_id, repos_relpath, revnum,
@@ -1012,7 +1010,6 @@
 DROP TABLE WORKING_NODE;
 
 PRAGMA user_version = 20;
-*/
 
 /* ------------------------------------------------------------------------- */
 
@@ -1028,81 +1025,6 @@
    number will be, however, so we're just marking it as 99 for now. */
 -- format: 99
 
-/* We cannot directly remove columns, so we use a temporary table instead. */
-/* First create the temporary table without the undesired column(s). */
-CREATE TEMPORARY TABLE BASE_NODE_BACKUP(
- wc_id INTEGER NOT NULL,
- local_relpath TEXT NOT NULL,
- repos_id INTEGER,
- repos_relpath TEXT,
- parent_relpath TEXT,
- presence TEXT NOT NULL,
- kind TEXT NOT NULL,
- revnum INTEGER,
- checksum TEXT,
- translated_size INTEGER,
- changed_rev INTEGER,
- changed_date INTEGER,
- changed_author TEXT,
- depth TEXT,
- symlink_target TEXT,
- last_mod_time INTEGER,
- properties BLOB,
- dav_cache BLOB,
- file_external TEXT
-);
-
-/* Copy everything into the temporary table. */
-INSERT INTO BASE_NODE_BACKUP SELECT
- wc_id, local_relpath, repos_id, repos_relpath, parent_relpath, presence,
- kind, revnum, checksum, translated_size, changed_rev, changed_date,
- changed_author, depth, symlink_target, last_mod_time, properties, dav_cache,
- file_external
-FROM BASE_NODE;
-
-/* Drop the original table. */
-DROP TABLE BASE_NODE;
-
-/* Recreate the original table, this time less the temporary columns.
- Column descriptions are same as BASE_NODE in format 12 */
-CREATE TABLE BASE_NODE(
- wc_id INTEGER NOT NULL REFERENCES WCROOT (id),
- local_relpath TEXT NOT NULL,
- repos_id INTEGER REFERENCES REPOSITORY (id),
- repos_relpath TEXT,
- parent_relpath TEXT,
- presence TEXT NOT NULL,
- kind TEXT NOT NULL,
- revnum INTEGER,
- checksum TEXT,
- translated_size INTEGER,
- changed_rev INTEGER,
- changed_date INTEGER,
- changed_author TEXT,
- depth TEXT,
- symlink_target TEXT,
- last_mod_time INTEGER,
- properties BLOB,
- dav_cache BLOB,
- file_external TEXT,
-
- PRIMARY KEY (wc_id, local_relpath)
- );
-
-/* Recreate the index. */
-CREATE INDEX I_PARENT ON BASE_NODE (wc_id, parent_relpath);
-
-/* Copy everything back into the original table. */
-INSERT INTO BASE_NODE SELECT
- wc_id, local_relpath, repos_id, repos_relpath, parent_relpath, presence,
- kind, revnum, checksum, translated_size, changed_rev, changed_date,
- changed_author, depth, symlink_target, last_mod_time, properties, dav_cache,
- file_external
-FROM BASE_NODE_BACKUP;
-
-/* Drop the temporary table. */
-DROP TABLE BASE_NODE_BACKUP;
-
 /* Now "drop" the tree_conflict_data column from actual_node. */
 CREATE TABLE ACTUAL_NODE_BACKUP (
   wc_id INTEGER NOT NULL,

-- 
Philip