Fix pg_dump's handling of DROP DATABASE commands in --clean mode.

In commit 4317e024, I accidentally broke
this behavior while rearranging code to ensure that --create wouldn't
affect whether a DATABASE entry gets put into archive-format output.
Thus, 9.2 would issue a DROP DATABASE command in --clean mode, which is
either useless or dangerous depending on the usage scenario.
It should not do that, and no longer does.

A bright spot is that this refactoring makes it easy to allow the
combination of --clean and --create to work sensibly, ie, emit DROP
DATABASE then CREATE DATABASE before reconnecting.  Ordinarily we'd
consider that a feature addition and not back-patch it, but it seems
silly to not include the extra couple of lines required in the 9.2
version of the code.

Per report from Guillaume Lelarge, though this is slightly more extensive
than his proposed patch.

doc/src/sgml/ref/pg_dump.sgml

@@ -143,7 +143,8 @@ PostgreSQL documentation
        <para>
         Output commands to clean (drop)
         database objects prior to outputting the commands for creating them.
-        (Restore might generate some harmless errors.)
+        (Restore might generate some harmless error messages, if any objects
+        were not present in the destination database.)
        </para>
 
        <para>
@@ -161,8 +162,10 @@ PostgreSQL documentation
        <para>
         Begin the output with a command to create the
         database itself and reconnect to the created database.  (With a
-        script of this form, it doesn't matter which database you connect
-        to before running the script.)
+        script of this form, it doesn't matter which database in the
+        destination installation you connect to before running the script.)
+        If <option>--clean</option> is also specified, the script drops and
+        recreates the target database before reconnecting to it.
        </para>
 
        <para>

doc/src/sgml/ref/pg_restore.sgml

@@ -109,6 +109,8 @@
       <listitem>
        <para>
         Clean (drop) database objects before recreating them.
+        (This might generate some harmless error messages, if any objects
+        were not present in the destination database.)
        </para>
       </listitem>
      </varlistentry>
@@ -118,11 +120,16 @@
       <term><option>--create</option></term>
       <listitem>
        <para>
-        Create the database before restoring into it.  (When this
-        option is used, the database named with <option>-d</option> is
-        used only to issue the initial <command>CREATE DATABASE</>
-        command.  All data is restored into the database name that
-        appears in the archive.)
+        Create the database before restoring into it.
+        If <option>--clean</option> is also specified, drop and
+        recreate the target database before connecting to it.
+       </para>
+
+       <para>
+        When this option is used, the database named with <option>-d</option>
+        is used only to issue the initial <command>DROP DATABASE</> and
+        <command>CREATE DATABASE</> commands.  All data is restored into the
+        database name that appears in the archive.
        </para>
       </listitem>
      </varlistentry>

src/bin/pg_dump/pg_backup_archiver.c

@@ -303,15 +303,6 @@ RestoreArchive(Archive *AHX)
 	/*
 	 * Check for nonsensical option combinations.
 	 *
-	 * NB: createDB+dropSchema is useless because if you're creating the DB,
-	 * there's no need to drop individual items in it.  Moreover, if we tried
-	 * to do that then we'd issue the drops in the database initially
-	 * connected to, not the one we will create, which is very bad...
-	 */
-	if (ropt->createDB && ropt->dropSchema)
-		exit_horribly(modulename, "-C and -c are incompatible options\n");
-
-	/*
 	 * -C is not compatible with -1, because we can't create a database inside
 	 * a transaction block.
 	 */
@@ -456,7 +447,25 @@ RestoreArchive(Archive *AHX)
 		{
 			AH->currentTE = te;
 
-			/* We want anything that's selected and has a dropStmt */
+			/*
+			 * In createDB mode, issue a DROP *only* for the database as a
+			 * whole.  Issuing drops against anything else would be wrong,
+			 * because at this point we're connected to the wrong database.
+			 * Conversely, if we're not in createDB mode, we'd better not
+			 * issue a DROP against the database at all.
+			 */
+			if (ropt->createDB)
+			{
+				if (strcmp(te->desc, "DATABASE") != 0)
+					continue;
+			}
+			else
+			{
+				if (strcmp(te->desc, "DATABASE") == 0)
+					continue;
+			}
+
+			/* Otherwise, drop anything that's selected and has a dropStmt */
 			if (((te->reqs & (REQ_SCHEMA | REQ_DATA)) != 0) && te->dropStmt)
 			{
 				ahlog(AH, 1, "dropping %s %s\n", te->desc, te->tag);
@@ -938,9 +947,6 @@ PrintTOCSummary(Archive *AHX, RestoreOptions *ropt)
 
 	ahprintf(AH, ";\n;\n; Selected TOC Entries:\n;\n");
 
-	/* We should print DATABASE entries whether or not -C was specified */
-	ropt->createDB = 1;
-
 	curSection = SECTION_PRE_DATA;
 	for (te = AH->toc->next; te != AH->toc; te = te->next)
 	{