Implement replace branch in BranchManager

paimon-core/src/main/java/org/apache/paimon/privilege/PrivilegedFileStoreTable.java

@@ -204,6 +204,12 @@ public void deleteBranch(String branchName) {
         wrapped.deleteBranch(branchName);
     }
 
+    @Override
+    public void replaceBranch(String fromBranch) {
+        privilegeChecker.assertCanInsert(identifier);
+        wrapped.replaceBranch(fromBranch);
+    }
+
     @Override
     public ExpireSnapshots newExpireSnapshots() {
         privilegeChecker.assertCanInsert(identifier);

paimon-core/src/main/java/org/apache/paimon/schema/SchemaManager.java

@@ -68,7 +68,6 @@
 import static org.apache.paimon.catalog.Identifier.UNKNOWN_DATABASE;
 import static org.apache.paimon.utils.BranchManager.DEFAULT_MAIN_BRANCH;
 import static org.apache.paimon.utils.BranchManager.getBranchPath;
-import static org.apache.paimon.utils.BranchManager.isMainBranch;
 import static org.apache.paimon.utils.FileUtils.listVersionedFiles;
 import static org.apache.paimon.utils.Preconditions.checkState;
 
@@ -500,17 +499,13 @@ public static TableSchema fromPath(FileIO fileIO, Path path) {
     }
 
     public Path schemaDirectory() {
-        return isMainBranch(branch)
-                ? new Path(tableRoot + "/schema")
-                : new Path(getBranchPath(tableRoot, branch) + "/schema");
+        return new Path(getBranchPath(fileIO, tableRoot, branch) + "/schema");
     }
 
     @VisibleForTesting
     public Path toSchemaPath(long schemaId) {
-        return isMainBranch(branch)
-                ? new Path(tableRoot + "/schema/" + SCHEMA_PREFIX + schemaId)
-                : new Path(
-                        getBranchPath(tableRoot, branch) + "/schema/" + SCHEMA_PREFIX + schemaId);
+        return new Path(
+                getBranchPath(fileIO, tableRoot, branch) + "/schema/" + SCHEMA_PREFIX + schemaId);
     }
 
     /**

paimon-core/src/main/java/org/apache/paimon/table/AbstractFileStoreTable.java

@@ -525,6 +525,11 @@ public void deleteBranch(String branchName) {
         branchManager().deleteBranch(branchName);
     }
 
+    @Override
+    public void replaceBranch(String fromBranch) {
+        branchManager().replaceBranch(fromBranch);
+    }
+
     @Override
     public void rollbackTo(String tagName) {
         TagManager tagManager = tagManager();

paimon-core/src/main/java/org/apache/paimon/table/ReadonlyTable.java

@@ -182,6 +182,14 @@ default void deleteBranch(String branchName) {
                         this.getClass().getSimpleName()));
     }
 
+    @Override
+    default void replaceBranch(String fromBranch) {
+        throw new UnsupportedOperationException(
+                String.format(
+                        "Readonly Table %s does not support replaceBranch.",
+                        this.getClass().getSimpleName()));
+    }
+
     @Override
     default ExpireSnapshots newExpireSnapshots() {
         throw new UnsupportedOperationException(

paimon-core/src/main/java/org/apache/paimon/table/Table.java

@@ -111,6 +111,9 @@ public interface Table extends Serializable {
     @Experimental
     void deleteBranch(String branchName);
 
+    @Experimental
+    void replaceBranch(String fromBranch);
+
     /** Manually expire snapshots, parameters can be controlled independently of table options. */
     @Experimental
     ExpireSnapshots newExpireSnapshots();

paimon-core/src/main/java/org/apache/paimon/utils/BranchManager.java

@@ -33,9 +33,12 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Optional;
 import java.util.PriorityQueue;
+import java.util.Set;
 import java.util.SortedMap;
 import java.util.stream.Collectors;
 
@@ -49,6 +52,7 @@ public class BranchManager {
 
     public static final String BRANCH_PREFIX = "branch-";
     public static final String DEFAULT_MAIN_BRANCH = "main";
+    public static final String MAIN_BRANCH_FILE = "MAIN-BRANCH";
 
     private final FileIO fileIO;
     private final Path tablePath;
@@ -69,6 +73,12 @@ public BranchManager(
         this.schemaManager = schemaManager;
     }
 
+    /** Commit specify branch to main. */
+    public void commitMainBranch(String branchName) throws IOException {
+        Path mainBranchFile = new Path(tablePath, MAIN_BRANCH_FILE);
+        fileIO.overwriteFileUtf8(mainBranchFile, branchName);
+    }
+
     /** Return the root Directory of branch. */
     public Path branchDirectory() {
         return new Path(tablePath + "/branch");
@@ -79,13 +89,45 @@ public static boolean isMainBranch(String branch) {
     }
 
     /** Return the path string of a branch. */
-    public static String getBranchPath(Path tablePath, String branchName) {
-        return tablePath.toString() + "/branch/" + BRANCH_PREFIX + branchName;
+    public static String getBranchPath(FileIO fileIO, Path tablePath, String branch) {
+        if (isMainBranch(branch)) {
+            Path path = new Path(tablePath, MAIN_BRANCH_FILE);
+            try {
+                if (fileIO.exists(path)) {
+                    String data = fileIO.readFileUtf8(path);
+                    if (StringUtils.isBlank(data)) {
+                        return tablePath.toString();
+                    } else {
+                        return tablePath.toString() + "/branch/" + BRANCH_PREFIX + data;
+                    }
+                } else {
+                    return tablePath.toString();
+                }
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return tablePath.toString() + "/branch/" + BRANCH_PREFIX + branch;
+    }
+
+    public String defaultMainBranch() {
+        Path path = new Path(tablePath, MAIN_BRANCH_FILE);
+        try {
+            if (fileIO.exists(path)) {
+                String data = fileIO.readFileUtf8(path);
+                if (!StringUtils.isBlank(data)) {
+                    return data;
+                }
+            }
+            return DEFAULT_MAIN_BRANCH;
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
     }
 
     /** Return the path of a branch. */
     public Path branchPath(String branchName) {
-        return new Path(getBranchPath(tablePath, branchName));
+        return new Path(getBranchPath(fileIO, tablePath, branchName));
     }
 
     /** Create empty branch. */
@@ -111,7 +153,7 @@ public void createBranch(String branchName) {
             throw new RuntimeException(
                     String.format(
                             "Exception occurs when create branch '%s' (directory in %s).",
-                            branchName, getBranchPath(tablePath, branchName)),
+                            branchName, getBranchPath(fileIO, tablePath, branchName)),
                     e);
         }
     }
@@ -143,17 +185,17 @@ public void createBranch(String branchName, long snapshotId) {
             throw new RuntimeException(
                     String.format(
                             "Exception occurs when create branch '%s' (directory in %s).",
-                            branchName, getBranchPath(tablePath, branchName)),
+                            branchName, getBranchPath(fileIO, tablePath, branchName)),
                     e);
         }
     }
 
     public void createBranch(String branchName, String tagName) {
+        String mainBranch = defaultMainBranch();
         checkArgument(
                 !isMainBranch(branchName),
                 String.format(
-                        "Branch name '%s' is the default branch and cannot be used.",
-                        DEFAULT_MAIN_BRANCH));
+                        "Branch name '%s' is the default branch and cannot be used.", mainBranch));
         checkArgument(!StringUtils.isBlank(branchName), "Branch name '%s' is blank.", branchName);
         checkArgument(!branchExists(branchName), "Branch name '%s' already exists.", branchName);
         checkArgument(tagManager.tagExists(tagName), "Tag name '%s' not exists.", tagName);
@@ -179,7 +221,7 @@ public void createBranch(String branchName, String tagName) {
             throw new RuntimeException(
                     String.format(
                             "Exception occurs when create branch '%s' (directory in %s).",
-                            branchName, getBranchPath(tablePath, branchName)),
+                            branchName, getBranchPath(fileIO, tablePath, branchName)),
                     e);
         }
     }
@@ -193,11 +235,110 @@ public void deleteBranch(String branchName) {
             LOG.info(
                     String.format(
                             "Deleting the branch failed due to an exception in deleting the directory %s. Please try again.",
-                            getBranchPath(tablePath, branchName)),
+                            getBranchPath(fileIO, tablePath, branchName)),
                     e);
         }
     }
 
+    /** Replace specify branch to main branch. */
+    public void replaceBranch(String branchName) {
+        String mainBranch = defaultMainBranch();
+        checkArgument(
+                !isMainBranch(branchName),
+                String.format(
+                        "Branch name '%s' is the default main branch and cannot be replaced repeatedly.",
+                        mainBranch));
+        checkArgument(!StringUtils.isBlank(branchName), "Branch name '%s' is blank.", branchName);
+        checkArgument(branchExists(branchName), "Branch name '%s' not exists.", branchName);
+        try {
+            // 0. Cache previous tag,snapshot,schema directory.
+            Path tagDirectory = tagManager.tagDirectory();
+            Path snapshotDirectory = snapshotManager.snapshotDirectory();
+            Path schemaDirectory = schemaManager.schemaDirectory();
+            // 1. Calculate and copy the snapshots, tags and schemas which should be copied from the
+            // main to branch.
+            calculateCopyMainToBranch(branchName);
+            // 2. Update the Main Branch File to the target branch.
+            commitMainBranch(branchName);
+            // 3.Drop the previous main branch, including snapshots, tags and schemas.
+            dropPreviousMainBranch(tagDirectory, snapshotDirectory, schemaDirectory);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /** Calculate copy main branch to target branch. */
+    private void calculateCopyMainToBranch(String branchName) throws IOException {
+        TableBranch fromBranch =
+                this.branches().stream()
+                        .filter(branch -> branch.getBranchName().equals(branchName))
+                        .findFirst()
+                        .orElse(null);
+        if (fromBranch == null) {
+            throw new RuntimeException(String.format("No branches found %s", branchName));
+        }
+        Snapshot fromSnapshot = snapshotManager.snapshot(fromBranch.getCreatedFromSnapshot());
+        // Copy tags.
+        List<String> tags = tagManager.allTagNames();
+        TagManager branchTagManager = tagManager.copyWithBranch(branchName);
+        for (String tagName : tags) {
+            if (branchTagManager.tagExists(tagName)) {
+                // If it already exists, skip it directly.
+                continue;
+            }
+            Snapshot snapshot = tagManager.taggedSnapshot(tagName);
+            if (snapshot.id() < fromSnapshot.id()) {
+                fileIO.copyFileUtf8(tagManager.tagPath(tagName), branchTagManager.tagPath(tagName));
+            }
+        }
+        // Copy snapshots.
+        Iterator<Snapshot> snapshots = snapshotManager.snapshots();
+        SnapshotManager branchSnapshotManager = snapshotManager.copyWithBranch(branchName);
+        while (snapshots.hasNext()) {
+            Snapshot snapshot = snapshots.next();
+            if (branchSnapshotManager.snapshotExists(snapshot.id())) {
+                // If it already exists, skip it directly.
+                continue;
+            }
+            if (snapshot.id() < fromSnapshot.id()) {
+                fileIO.copyFileUtf8(
+                        snapshotManager.snapshotPath(snapshot.id()),
+                        branchSnapshotManager.snapshotPath(snapshot.id()));
+            }
+        }
+
+        // Copy schemas.
+        List<Long> schemaIds = schemaManager.listAllIds();
+        SchemaManager branchSchemaManager = schemaManager.copyWithBranch(branchName);
+        Set<Long> existsSchemas = new HashSet<>(branchSchemaManager.listAllIds());
+
+        for (Long schemaId : schemaIds) {
+            if (existsSchemas.contains(schemaId)) {
+                // If it already exists, skip it directly.
+                continue;
+            }
+            TableSchema tableSchema = schemaManager.schema(schemaId);
+            if (tableSchema.id() < fromSnapshot.schemaId()) {
+                fileIO.copyFileUtf8(
+                        schemaManager.toSchemaPath(schemaId),
+                        branchSchemaManager.toSchemaPath(schemaId));
+            }
+        }
+    }
+
+    /** Directly delete snapshot, tag , schema directory. */
+    private void dropPreviousMainBranch(
+            Path tagDirectory, Path snapshotDirectory, Path schemaDirectory) throws IOException {
+        // Delete tags.
+        fileIO.delete(tagDirectory, true);
+
+        // Delete snapshots.
+        fileIO.delete(snapshotDirectory, true);
+
+        // Delete schemas.
+        fileIO.delete(schemaDirectory, true);
+    }
+
     /** Check if path exists. */
     public boolean fileExists(Path path) {
         try {
@@ -246,8 +387,7 @@ public List<TableBranch> branches() {
                 }
                 FileStoreTable branchTable =
                         FileStoreTableFactory.create(
-                                fileIO, new Path(getBranchPath(tablePath, branchName)));
-
+                                fileIO, new Path(getBranchPath(fileIO, tablePath, branchName)));
                 SortedMap<Snapshot, List<String>> snapshotTags = branchTable.tagManager().tags();
                 Long earliestSnapshotId = branchTable.snapshotManager().earliestSnapshotId();
                 if (snapshotTags.isEmpty()) {

paimon-core/src/main/java/org/apache/paimon/utils/SnapshotManager.java

@@ -47,7 +47,6 @@
 
 import static org.apache.paimon.utils.BranchManager.DEFAULT_MAIN_BRANCH;
 import static org.apache.paimon.utils.BranchManager.getBranchPath;
-import static org.apache.paimon.utils.BranchManager.isMainBranch;
 import static org.apache.paimon.utils.FileUtils.listVersionedFiles;
 
 /** Manager for {@link Snapshot}, providing utility methods related to paths and snapshot hints. */
@@ -90,35 +89,27 @@ public Path tablePath() {
     }
 
     public Path changelogDirectory() {
-        return isMainBranch(branch)
-                ? new Path(tablePath + "/changelog")
-                : new Path(getBranchPath(tablePath, branch) + "/changelog");
+        return new Path(getBranchPath(fileIO, tablePath, branch) + "/changelog");
     }
 
     public Path longLivedChangelogPath(long snapshotId) {
-        return isMainBranch(branch)
-                ? new Path(tablePath + "/changelog/" + CHANGELOG_PREFIX + snapshotId)
-                : new Path(
-                        getBranchPath(tablePath, branch)
-                                + "/changelog/"
-                                + CHANGELOG_PREFIX
-                                + snapshotId);
+        return new Path(
+                getBranchPath(fileIO, tablePath, branch)
+                        + "/changelog/"
+                        + CHANGELOG_PREFIX
+                        + snapshotId);
     }
 
     public Path snapshotPath(long snapshotId) {
-        return isMainBranch(branch)
-                ? new Path(tablePath + "/snapshot/" + SNAPSHOT_PREFIX + snapshotId)
-                : new Path(
-                        getBranchPath(tablePath, branch)
-                                + "/snapshot/"
-                                + SNAPSHOT_PREFIX
-                                + snapshotId);
+        return new Path(
+                getBranchPath(fileIO, tablePath, branch)
+                        + "/snapshot/"
+                        + SNAPSHOT_PREFIX
+                        + snapshotId);
     }
 
     public Path snapshotDirectory() {
-        return isMainBranch(branch)
-                ? new Path(tablePath + "/snapshot")
-                : new Path(getBranchPath(tablePath, branch) + "/snapshot");
+        return new Path(getBranchPath(fileIO, tablePath, branch) + "/snapshot");
     }
 
     public Snapshot snapshot(long snapshotId) {