[CALCITE-7393] Support RelDataTypeDigest

use RelDataTypeDigest to reduce composite type's digest
memory and digest relative operation's latency

This is a break change, computeDigest will not set the string
digest field, and innerDigest will be initialized by default.
We recommend users use innerDigest to replace legacy string digest
to archive better memory/latency for nested types.

For users rely on set String digest for UDT, we keep the old behavior
of hashCode/equals.

Author: zhuwenzhuang

core/src/main/java/org/apache/calcite/jdbc/JavaRecordType.java

@@ -41,14 +41,15 @@ public JavaRecordType(List<RelDataTypeField> fields, Class clazz) {
     this.clazz = requireNonNull(clazz, "clazz");
   }
 
-  @Override public boolean equals(@Nullable Object obj) {
+  @Override public boolean deepEquals(@Nullable Object obj) {
     return this == obj
         || obj instanceof JavaRecordType
         && Objects.equals(fieldList, ((JavaRecordType) obj).fieldList)
-        && clazz == ((JavaRecordType) obj).clazz;
+        && clazz == ((JavaRecordType) obj).clazz
+        && this.isNullable() == ((JavaRecordType) obj).isNullable();
   }
 
-  @Override public int hashCode() {
-    return Objects.hash(fieldList, clazz);
+  @Override public int deepHashCode() {
+    return Objects.hash(fieldList, this.isNullable(), clazz);
   }
 }

core/src/main/java/org/apache/calcite/rel/HasDigestString.java

@@ -0,0 +1,24 @@
+/*
+ * 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.calcite.rel;
+
+/**
+ * Interface for objects that have a digest string.
+ */
+public interface HasDigestString {
+  String getDigestString();
+}

core/src/main/java/org/apache/calcite/rel/type/RelDataType.java

@@ -322,4 +322,26 @@ default boolean equalsSansFieldNamesAndNullability(@Nullable RelDataType that) {
   default boolean isMeasure() {
     return getSqlTypeName() == SqlTypeName.MEASURE;
   }
+
+  /**
+   * Returns the digest of this type.
+   *
+   * @return digest of this type
+   */
+  RelDataTypeDigest getDigest();
+
+  /**
+   * Deep equality check for RelDataType digest.
+   *
+   * @return Whether the 2 RelDataTypes are equivalent or have the same digest.
+   * @see #deepHashCode()
+   */
+  boolean deepEquals(@Nullable Object obj);
+
+  /**
+   * Compute deep hash code for RelDataType digest.
+   *
+   * @see #deepEquals(Object)
+   */
+  int deepHashCode();
 }

core/src/main/java/org/apache/calcite/rel/type/RelDataTypeDigest.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.calcite.rel.type;
+
+import org.apache.calcite.rel.HasDigestString;
+
+/**
+ * Digest of a RelDataType.
+ */
+public interface RelDataTypeDigest extends HasDigestString {
+  RelDataType getType();
+}

core/src/main/java/org/apache/calcite/rel/type/RelDataTypeImpl.java

@@ -46,8 +46,8 @@
  * RelDataTypeImpl is an abstract base for implementations of
  * {@link RelDataType}.
  *
- * <p>Identity is based upon the {@link #digest} field, which each derived class
- * should set during construction.
+ * <p>Identity is based upon the {@link #digest} or {@link #innerDigest} field,
+ * which each derived class should set {@link #digest} or {@link #innerDigest} during construction.
  */
 public abstract class RelDataTypeImpl
     implements RelDataType, RelDataTypeFamily {
@@ -60,7 +60,8 @@ public abstract class RelDataTypeImpl
   //~ Instance fields --------------------------------------------------------
 
   protected final @Nullable List<RelDataTypeField> fieldList;
-  protected @Nullable String digest;
+  protected @Deprecated @Nullable String digest;
+  protected @Nullable RelDataTypeDigest innerDigest;
 
   //~ Constructors -----------------------------------------------------------
 
@@ -232,18 +233,50 @@ private static void getFieldRecurse(List<Slot> slots, RelDataType type,
     return fieldList != null;
   }
 
-  @Override public boolean equals(@Nullable Object obj) {
-    return this == obj
-        || obj instanceof RelDataTypeImpl
-        && Objects.equals(this.digest, ((RelDataTypeImpl) obj).digest);
+  /**
+   * Gets the {@link RelDataTypeDigest} of this type.
+   * If a user has set the legacy string {@code digest} and {@code innerDigest} has not
+   * been initialized yet, this method computes and initializes it.
+   */
+  @Override public RelDataTypeDigest getDigest() {
+    if (digest != null && innerDigest == null) {
+      computeDigest();
+    }
+    return requireNonNull(innerDigest, "innerDigest");
+  }
+
+  @Override public final boolean equals(@Nullable Object obj) {
+    if (obj == this) {
+      return true;
+    }
+    if (obj instanceof RelDataTypeImpl) {
+      final RelDataTypeImpl that = (RelDataTypeImpl) obj;
+      return this.getDigest().equals(that.getDigest());
+    }
+    return false;
   }
 
-  @Override public int hashCode() {
-    return Objects.hashCode(digest);
+  @Override public final int hashCode() {
+    return getDigest().hashCode();
+  }
+
+  @Override public boolean deepEquals(@Nullable Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (obj == null || this.getClass() != obj.getClass()) {
+      return false;
+    }
+    return Objects.equals(this.getDigest().getDigestString(),
+        ((RelDataTypeImpl) obj).getDigest().getDigestString());
+  }
+
+  @Override public int deepHashCode() {
+    return Objects.hashCode(this.getDigest().getDigestString());
   }
 
   @Override public String getFullTypeString() {
-    return requireNonNull(digest, "digest");
+    return requireNonNull(this.getDigest().getDigestString(), "digest");
   }
 
   @Override public boolean isNullable() {
@@ -309,23 +342,81 @@ protected abstract void generateTypeString(
       boolean withDetail);
 
   /**
-   * Computes the digest field. This should be called in every non-abstract
-   * subclass constructor once the type is fully defined.
+   * Init the lazy digest computing field {@link #innerDigest}.
+   * This should be called in every non-abstract subclass
+   * constructor once the type is fully defined.
    */
   @SuppressWarnings("method.invocation.invalid")
   protected void computeDigest(@UnknownInitialization RelDataTypeImpl this) {
-    StringBuilder sb = new StringBuilder();
-    generateTypeString(sb, true);
-    if (!isNullable()) {
-      sb.append(NON_NULLABLE_SUFFIX);
-    }
-    digest = sb.toString();
+    innerDigest = new InnerRelDataTypeDigest();
   }
 
   @Override public String toString() {
-    StringBuilder sb = new StringBuilder();
-    generateTypeString(sb, false);
-    return sb.toString();
+    return getDigest().toString();
+  }
+
+  /** Implementation of {@link RelDataTypeDigest}. */
+  private class InnerRelDataTypeDigest implements RelDataTypeDigest {
+    /** Cached hash code. */
+    private int hash = 0;
+    /** Cached type string. */
+    private @Nullable String digestWithDetail = null;  // NOTE: shorter detail will be better
+    private @Nullable String digestWithoutDetail = null;
+
+    @Override public RelDataType getType() {
+      return RelDataTypeImpl.this;
+    }
+
+    @Override public boolean equals(@Nullable Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (o == null || getClass() != o.getClass()) {
+        return false;
+      }
+      final RelDataTypeImpl.InnerRelDataTypeDigest otherDigest =
+          (RelDataTypeImpl.InnerRelDataTypeDigest) o;
+      if (digest != null) {
+        return digest.equals(otherDigest.getDigestString());
+      }
+      return deepEquals(otherDigest.getType());
+    }
+
+    @Override public int hashCode() {
+      if (digest != null) {
+        return Objects.hashCode(digest);
+      }
+      if (hash == 0) {
+        hash = deepHashCode();
+      }
+      return hash;
+    }
+
+    @Override public String getDigestString() {
+      // return user defined digest by set legacy digest string field.
+      if (digest != null) {
+        return digest;
+      }
+
+      if (digestWithDetail == null) {
+        StringBuilder sb = new StringBuilder();
+        generateTypeString(sb, true);
+        if (!isNullable()) {
+          sb.append(NON_NULLABLE_SUFFIX);
+        }
+        digestWithDetail = sb.toString();
+      }
+      return digestWithDetail;
+    }
+
+    @Override public String toString() {
+      if (digestWithoutDetail == null) {
+        StringBuilder sb = new StringBuilder();
+        RelDataTypeImpl.this.generateTypeString(sb, false);
+        digestWithoutDetail = sb.toString();
+      }
+      return digestWithoutDetail;
+    }
   }
 
   @Override public RelDataTypePrecedenceList getPrecedenceList() {

core/src/main/java/org/apache/calcite/rel/type/RelRecordType.java

@@ -27,6 +27,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import static java.util.Objects.requireNonNull;
 
@@ -146,6 +147,39 @@ public RelRecordType(List<RelDataTypeField> fields) {
     sb.append(")");
   }
 
+  @Override public boolean deepEquals(@Nullable Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (obj == null || this.getClass() != obj.getClass()) {
+      return false;
+    }
+
+    RelRecordType that = (RelRecordType) obj;
+    if (kind != that.kind || nullable != that.nullable) {
+      return false;
+    }
+
+    if (fieldList == null || that.fieldList == null) {
+      return fieldList == null && that.fieldList == null;
+    }
+
+    if (fieldList.size() != that.fieldList.size()) {
+      return false;
+    }
+
+    for (int i = 0; i < fieldList.size(); i++) {
+      if (!fieldList.get(i).equals(that.fieldList.get(i))) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @Override public int deepHashCode() {
+    return Objects.hash(kind.ordinal(), nullable, fieldList);
+  }
+
   /**
    * Per {@link Serializable} API, provides a replacement object to be written
    * during serialization.

core/src/main/java/org/apache/calcite/rel/type/SingleColumnAliasRelDataType.java

@@ -136,4 +136,16 @@ public SingleColumnAliasRelDataType(RelDataType original, RelDataType alias) {
   @Override public boolean isDynamicStruct() {
     return original.isDynamicStruct();
   }
+
+  @Override public RelDataTypeDigest getDigest() {
+    return original.getDigest();
+  }
+
+  @Override public boolean deepEquals(@Nullable Object obj) {
+    return original.deepEquals(obj);
+  }
+
+  @Override public int deepHashCode() {
+    return original.deepHashCode();
+  }
 }

core/src/main/java/org/apache/calcite/sql/type/ArraySqlType.java

@@ -20,6 +20,10 @@
 import org.apache.calcite.rel.type.RelDataTypeFamily;
 import org.apache.calcite.rel.type.RelDataTypePrecedenceList;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import java.util.Objects;
+
 import static org.apache.calcite.sql.type.NonNullableAccessors.getComponentTypeOrThrow;
 
 import static java.util.Objects.requireNonNull;
@@ -56,6 +60,21 @@ public ArraySqlType(RelDataType elementType, boolean isNullable) {
     sb.append(" ARRAY");
   }
 
+  @Override public boolean deepEquals(@Nullable Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (obj == null || this.getClass() != obj.getClass()) {
+      return false;
+    }
+    ArraySqlType that = (ArraySqlType) obj;
+    return this.isNullable() == that.isNullable() && elementType.equals(that.elementType);
+  }
+
+  @Override public int deepHashCode() {
+    return Objects.hash(SqlTypeName.ARRAY.ordinal(), isNullable, elementType.hashCode());
+  }
+
   // implement RelDataType
   @Override public RelDataType getComponentType() {
     return elementType;