mdbx-load: add -p option (purge subDB).

Change-Id: I678950c99c8b4aea1add4ce548c9b4fe4ab8bfe6

ChangeLog.md

@@ -21,11 +21,12 @@ Removed options and features:
 
  - Drop `MDBX_HUGE_TRANSACTIONS` build-option (now no longer required).
 
-Added features:
+New features:
 
  - Package for FreeBSD is available now by Mahlon E. Smith.
  - New API functions to get/set various options (https://github.com/erthink/libmdbx/issues/128).
  - Unlimited/Dynamic size of retired and dirty page lists (https://github.com/erthink/libmdbx/issues/123).
+ - Added `-p` option (purge subDB before loading) to `mdbx_load` tool.
 
 Fixes:
 

src/mdbx_load.c

@@ -448,16 +448,17 @@ static int readline(MDBX_val *out, MDBX_val *buf) {
 
 static void usage(void) {
   fprintf(stderr,
-          "usage: %s [-V] [-q] [-a] [-f file] [-s name] [-N] [-T] [-r] [-n]"
-          " dbpath\n"
+          "usage: %s "
+          "[-V] [-q] [-a] [-f file] [-s name] [-N] [-p] [-T] [-r] [-n] dbpath\n"
           "  -V\t\tprint version and exit\n"
           "  -q\t\tbe quiet\n"
           "  -a\t\tappend records in input order (required for custom "
           "comparators)\n"
           "  -f file\tread from file instead of stdin\n"
           "  -s name\tload into named subDB\n"
-          "  -N\t\tdon't overwrite existing records when loading (), just skip "
-          "them\n"
+          "  -N\t\tdon't overwrite existing records when loading, just skip "
+          "ones\n"
+          "  -p\t\tpurge subDB before loading\n"
           "  -T\t\tread plaintext\n"
           "  -r\t\trescue mode (ignore errors to load corrupted DB dump)\n"
           "  -n\t\tdon't use subdirectory for newly created database "
@@ -483,12 +484,13 @@ int main(int argc, char *argv[]) {
   int envflags = MDBX_SAFE_NOSYNC | MDBX_ACCEDE, putflags = MDBX_UPSERT;
   bool quiet = false;
   bool rescue = false;
+  bool purge = false;
 
   prog = argv[0];
   if (argc < 2)
     usage();
 
-  while ((i = getopt(argc, argv, "af:ns:NTVrq")) != EOF) {
+  while ((i = getopt(argc, argv, "af:ns:NpTVrq")) != EOF) {
     switch (i) {
     case 'V':
       printf("mdbx_load version %d.%d.%d.%d\n"
@@ -523,6 +525,9 @@ int main(int argc, char *argv[]) {
     case 'N':
       putflags |= MDBX_NOOVERWRITE | MDBX_NODUPDATA;
       break;
+    case 'p':
+      purge = true;
+      break;
     case 'T':
       mode |= NOHDR | PRINT;
       break;
@@ -696,6 +701,14 @@ int main(int argc, char *argv[]) {
       }
     }
 
+    if (purge) {
+      rc = mdbx_drop(txn, dbi, false);
+      if (unlikely(rc != MDBX_SUCCESS)) {
+        error("mdbx_drop", rc);
+        goto txn_abort;
+      }
+    }
+
     if (putflags & MDBX_APPEND)
       putflags = (dbi_flags & MDBX_DUPSORT) ? putflags | MDBX_APPENDDUP
                                             : putflags & ~MDBX_APPENDDUP;