Skip zero-length files for block incremental delta restore.

a42614e introduced the capability to preserve smaller than expected files for block incremental restore delta, but failed to take into account that zero-length files are both useless and cause the block checksum filter to error.

Fix this by skipping zero-length files during block incremental restore delta.

doc/xml/release/2024/2.51.xml

@@ -1,5 +1,21 @@
 <release date="XXXX-XX-XX" version="2.51dev" title="UNDER DEVELOPMENT">
     <release-core-list>
+        <release-bug-list>
+            <release-item>
+                <github-issue id="2271"/>
+                <github-pull-request id="2272"/>
+
+                <release-item-contributor-list>
+                    <release-item-ideator id="sebastian.krause"/>
+                    <release-item-contributor id="david.steele"/>
+                    <release-item-reviewer id="sebastian.krause"/>
+                    <release-item-reviewer id="rene.hojbjerg.larsen"/>
+                </release-item-contributor-list>
+
+                <p>Skip zero-length files for block incremental delta restore.</p>
+            </release-item>
+        </release-bug-list>
+
         <release-improvement-list>
             <release-item>
                 <github-pull-request id="2263"/>

doc/xml/release/contributor.xml

@@ -855,6 +855,11 @@
     <contributor-id type="github">vidierr</contributor-id>
 </contributor>
 
+<contributor id="rene.hojbjerg.larsen">
+    <contributor-name-display>Ren&amp;eacute; H&amp;oslash;jbjerg Larsen</contributor-name-display>
+    <contributor-id type="github">rhl-jfm</contributor-id>
+</contributor>
+
 <contributor id="robert.donovan">
     <contributor-name-display>Robert Donovan</contributor-name-display>
     <contributor-id type="github">rob-donovan</contributor-id>
@@ -910,6 +915,11 @@
     <contributor-id type="github">slardiere</contributor-id>
 </contributor>
 
+<contributor id="sebastian.krause">
+    <contributor-name-display>Sebastian Krause</contributor-name-display>
+    <contributor-id type="github">sekrause</contributor-id>
+</contributor>
+
 <contributor id="seth.daniel">
     <contributor-name-display>Seth Daniel</contributor-name-display>
     <contributor-id type="github">sethdaniel</contributor-id>

src/command/restore/file.c

@@ -88,8 +88,10 @@ restoreFile(
                         // Else use size and checksum
                         else
                         {
-                            // Only continue delta if the file size is as expected or larger
+                            // Only continue delta if the file size is as expected or larger (for normal files) or if block
-                            if (info.size >= file->size || file->blockIncrMapSize != 0)
+                            // incremental and the file to delta is not zero-length. Block incremental can potentially use almost
+                            // any portion of an existing file, but of course zero-length files do not have anything to reuse.
+                            if (info.size >= file->size || (file->blockIncrMapSize != 0 && info.size != 0))
                             {
                                 const char *const fileName = strZ(storagePathP(storagePg(), file->name));
 

test/src/module/command/restoreTest.c

@@ -3165,6 +3165,13 @@ testRun(void)
 
         HRN_STORAGE_PUT(storagePgWrite(), PG_PATH_BASE "/1/2", relation, .timeModified = timeBase - 2);
 
+        // Zeroed file large enough to use block incr (that will be truncated to zero before restore)
+        relation = bufNew(16 * 1024);
+        memset(bufPtr(relation), 0, bufSize(relation));
+        bufUsedSet(relation, bufSize(relation));
+
+        HRN_STORAGE_PUT(storagePgWrite(), PG_PATH_BASE "/1/44", relation, .timeModified = timeBase - 2);
+
         // Add postgresql.auto.conf to contain recovery settings
         HRN_STORAGE_PUT_EMPTY(storagePgWrite(), PG_FILE_POSTGRESQLAUTOCONF, .timeModified = timeBase - 1);
 
@@ -3234,6 +3241,7 @@ testRun(void)
             "base/1/\n"
             "base/1/2\n"
             "base/1/3\n"
+            "base/1/44\n"
             "global/\n"
             "global/pg_control\n"
             "postgresql.auto.conf\n",
@@ -3245,6 +3253,9 @@ testRun(void)
         // Use detail log level to catch block incremental restore message
         harnessLogLevelSet(logLevelDetail);
 
+        // Truncate file to ensure delta is skipped
+        HRN_STORAGE_PUT_EMPTY(storagePgWrite(), PG_PATH_BASE "/1/44");
+
         // Shrink file to make sure block incremental delta will reuse it
         relation = bufNew(128 * 1024);
         memset(bufPtr(relation), 0, bufSize(relation));
@@ -3271,6 +3282,7 @@ testRun(void)
             "base/1/\n"
             "base/1/2\n"
             "base/1/3\n"
+            "base/1/44\n"
             "global/\n"
             "global/pg_control\n"
             "postgresql.auto.conf\n",