Re: [PR] [core] Add cache for snapshots and schemas [paimon]

["wwj6591812 (via GitHub)" <gi...@apache.org>]

wwj6591812 commented on code in PR #4565:
URL: https://github.com/apache/paimon/pull/4565#discussion_r1853175781


##########
paimon-core/src/main/java/org/apache/paimon/catalog/CachingCatalog.java:
##########
@@ -316,4 +319,36 @@ public void refreshPartitions(Identifier identifier) throws TableNotExistExcepti
             partitionCache.put(identifier, result);
         }
     }
+
+    // ====================== cache for snapshot and schema files ================================
+
+    public static final Cache<Path, Snapshot> SNAPSHOT_CACHE =
+            Caffeine.newBuilder()
+                    .softValues()
+                    .expireAfterAccess(Duration.ofMinutes(10))
+                    .maximumSize(300)
+                    .executor(Runnable::run)
+                    .build();
+
+    public static final Cache<Path, TableSchema> SCHEMA_CACHE =
+            Caffeine.newBuilder()
+                    .softValues()
+                    .expireAfterAccess(Duration.ofMinutes(10))
+                    .maximumSize(100)
+                    .executor(Runnable::run)
+                    .build();
+
+    public static void invalidateMetaCacheForPrefix(Path tablePath) {
+        String path = tablePath.toString();
+        invalidateMetaCacheForPrefix(SNAPSHOT_CACHE, path);
+        invalidateMetaCacheForPrefix(SCHEMA_CACHE, path);
+    }
+
+    private static void invalidateMetaCacheForPrefix(Cache<Path, ?> cache, String tablePath) {

Review Comment:
   May be invalidateMetaCacheByPrefix?



##########
paimon-core/src/main/java/org/apache/paimon/tag/Tag.java:
##########
@@ -201,4 +179,28 @@ public boolean equals(Object o) {
         return Objects.equals(tagCreateTime, that.tagCreateTime)
                 && Objects.equals(tagTimeRetained, that.tagTimeRetained);
     }
+
+    // =================== Utils for reading =========================
+
+    public static Tag fromJson(String json) {
+        return JsonSerdeUtil.fromJson(json, Tag.class);
+    }
+
+    public static Tag fromPath(FileIO fileIO, Path path) {
+        try {
+            return tryFromPath(fileIO, path);
+        } catch (FileNotFoundException e) {
+            throw new RuntimeException(e.getMessage(), e);
+        }
+    }
+
+    public static Tag tryFromPath(FileIO fileIO, Path path) throws FileNotFoundException {

Review Comment:
   Why not cache Tag and Changelog like Snapshot？



##########
paimon-core/src/main/java/org/apache/paimon/Snapshot.java:
##########
@@ -437,4 +413,41 @@ public enum CommitKind {
         /** Collect statistics. */
         ANALYZE
     }
+
+    // =================== Utils for reading =========================
+
+    public static Snapshot fromJson(String json) {
+        return JsonSerdeUtil.fromJson(json, Snapshot.class);
+    }
+
+    public static Snapshot fromPath(FileIO fileIO, Path path) {
+        try {
+            return tryFromPath(fileIO, path);
+        } catch (FileNotFoundException e) {
+            String errorMessage =
+                    String.format(
+                            "Snapshot file %s does not exist. "
+                                    + "It might have been expired by other jobs operating on this table. "
+                                    + "In this case, you can avoid concurrent modification issues by configuring "
+                                    + "write-only = true and use a dedicated compaction job, or configuring "
+                                    + "different expiration thresholds for different jobs.",
+                            path);
+            throw new RuntimeException(errorMessage, e);
+        }
+    }
+
+    public static Snapshot tryFromPath(FileIO fileIO, Path path) throws FileNotFoundException {
+        try {
+            Snapshot snapshot = SNAPSHOT_CACHE.getIfPresent(path);
+            if (snapshot == null) {
+                snapshot = Snapshot.fromJson(fileIO.readFileUtf8(path));
+                SNAPSHOT_CACHE.put(path, snapshot);
+            }
+            return snapshot;
+        } catch (FileNotFoundException e) {

Review Comment:
   May be we can only catch IOException? There's no need to catch FileNotFoundException and throw it direct?



##########
paimon-hive/paimon-hive-catalog/src/main/java/org/apache/paimon/hive/HiveCatalog.java:
##########
@@ -680,6 +681,9 @@ protected void dropTableImpl(Identifier identifier) {
                                     false,
                                     true));
 
+            Path path = getTableLocation(identifier);
+            invalidateMetaCacheForPrefix(path);

Review Comment:
   May invalidateMetaCacheForPrefix(path) can execute in AbstractCatalog#dropTable after dropTableImpl(identifier)?
   Because If a new Catalog @Override AbstractCatalog#dropTableImpl, it may forget to call invalidateMetaCacheForPrefix(path).
   



##########
paimon-core/src/main/java/org/apache/paimon/utils/MetaCacheManager.java:
##########
@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.paimon.utils;
+
+import org.apache.paimon.Snapshot;
+import org.apache.paimon.schema.TableSchema;
+import org.apache.paimon.tag.Tag;
+
+/** Cache for {@link Snapshot} and {@link Tag} and {@link TableSchema}. */

Review Comment:
   Is this class reserved for future use?



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