[GitHub] [calcite] pengzhiwei2018 commented on a change in pull request #1181: [CALCITE-3016] Add sql dialect table operator factory to support all …

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pengzhiwei2018 commented on a change in pull request #1181: [CALCITE-3016] Add sql dialect table operator factory to support all …
URL: https://github.com/apache/calcite/pull/1181#discussion_r278833951
 
 

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 File path: core/src/main/java/org/apache/calcite/sql/fun/SqlDialectOperatorTableFactory.java
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+/*
+ * 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.sql.fun;
+
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.RelDataTypeFactory;
+import org.apache.calcite.sql.SqlFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlIdentifier;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.SqlOperator;
+import org.apache.calcite.sql.SqlOperatorTable;
+import org.apache.calcite.sql.SqlSyntax;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.ReturnTypes;
+import org.apache.calcite.sql.type.SqlReturnTypeInference;
+import org.apache.calcite.sql.type.SqlTypeTransforms;
+import org.apache.calcite.sql.util.ListSqlOperatorTable;
+import org.apache.calcite.sql.validate.SqlNameMatcher;
+import org.apache.calcite.util.Util;
+
+import com.google.common.base.Preconditions;
+
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.apache.calcite.sql.fun.SqlFlavor.Flavor;
+
+/**
+ * Operator table factory for multiple sql dialects. You can use method
+ * {@link #getOperatorTable} to fetch dialect specific operator table.
+ *
+ * <p>If you want to extend the sql dialect, add the sql dialect in {@link SqlFlavor},
+ * if the sql dialect already exists, and you want to add a sql function, annotate the function
+ * with the specific sql dialects that function belongs.
+ */
+public class SqlDialectOperatorTableFactory {
+
+  //~ Instance fields --------------------------------------------------------
+
+  // The singleton SqlDialectOperatorTableFactory instance.
+  private static SqlDialectOperatorTableFactory instance = null;
+
+  // Flag to indicate if this operator table has been initialized.
+  private boolean initialized = false;
+
+  // A container holding the operators for all the sql dialects.
+  private final Map<Flavor, ListSqlOperatorTable> dialectSqlOperatorTableMapping =
+      new HashMap<>();
+
+  /** Return type inference for {@code DECODE}. */
+  protected static final SqlReturnTypeInference DECODE_RETURN_TYPE =
+      opBinding -> {
+        final List<RelDataType> list = new ArrayList<>();
+        for (int i = 1, n = opBinding.getOperandCount(); i < n; i++) {
+          if (i < n - 1) {
+            ++i;
+          }
+          list.add(opBinding.getOperandType(i));
+        }
+        final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
+        RelDataType type = typeFactory.leastRestrictive(list);
+        if (opBinding.getOperandCount() % 2 == 1) {
+          type = typeFactory.createTypeWithNullability(type, true);
+        }
+        return type;
+      };
+
+  /** The "DECODE(v, v1, result1, [v2, result2, ...], resultN)" function. */
+  @SqlFlavor(flavors = {Flavor.ORACLE})
+  public static final SqlFunction DECODE =
+      new SqlFunction("DECODE", SqlKind.DECODE, DECODE_RETURN_TYPE, null,
+          OperandTypes.VARIADIC, SqlFunctionCategory.SYSTEM);
+
+  /** The "NVL(value, value)" function. */
+  @SqlFlavor(flavors = {Flavor.ORACLE})
+  public static final SqlFunction NVL =
+      new SqlFunction("NVL", SqlKind.NVL,
+          ReturnTypes.cascade(ReturnTypes.LEAST_RESTRICTIVE,
+              SqlTypeTransforms.TO_NULLABLE_ALL),
+          null, OperandTypes.SAME_SAME, SqlFunctionCategory.SYSTEM);
+
+  /** The "LTRIM(string)" function. */
+  @SqlFlavor(flavors = {Flavor.ORACLE})
+  public static final SqlFunction LTRIM =
+      new SqlFunction("LTRIM", SqlKind.LTRIM,
+          ReturnTypes.cascade(ReturnTypes.ARG0, SqlTypeTransforms.TO_NULLABLE,
+              SqlTypeTransforms.TO_VARYING), null,
+          OperandTypes.STRING, SqlFunctionCategory.STRING);
+
+  /** The "RTRIM(string)" function. */
+  @SqlFlavor(flavors = {Flavor.ORACLE})
+  public static final SqlFunction RTRIM =
+      new SqlFunction("RTRIM", SqlKind.RTRIM,
+          ReturnTypes.cascade(ReturnTypes.ARG0, SqlTypeTransforms.TO_NULLABLE,
+              SqlTypeTransforms.TO_VARYING), null,
+          OperandTypes.STRING, SqlFunctionCategory.STRING);
+
+  /** Oracle's "SUBSTR(string, position [, substringLength ])" function.
+   *
+   * <p>It has similar semantics to standard SQL's
+   * {@link SqlStdOperatorTable#SUBSTRING} function but different syntax. */
+  @SqlFlavor(flavors = {SqlFlavor.Flavor.ORACLE})
+  public static final SqlFunction SUBSTR =
+      new SqlFunction("SUBSTR", SqlKind.OTHER_FUNCTION,
+          ReturnTypes.ARG0_NULLABLE_VARYING, null, null,
+          SqlFunctionCategory.STRING);
+
+  /** The "GREATEST(value, value)" function. */
+  @SqlFlavor(flavors = {SqlFlavor.Flavor.ORACLE})
+  public static final SqlFunction GREATEST =
+      new SqlFunction("GREATEST", SqlKind.GREATEST,
+          ReturnTypes.cascade(ReturnTypes.LEAST_RESTRICTIVE,
+              SqlTypeTransforms.TO_NULLABLE), null,
+          OperandTypes.SAME_VARIADIC, SqlFunctionCategory.SYSTEM);
+
+  /** The "LEAST(value, value)" function. */
+  @SqlFlavor(flavors = {Flavor.ORACLE})
+  public static final SqlFunction LEAST =
+      new SqlFunction("LEAST", SqlKind.LEAST,
+          ReturnTypes.cascade(ReturnTypes.LEAST_RESTRICTIVE,
+              SqlTypeTransforms.TO_NULLABLE), null,
+          OperandTypes.SAME_VARIADIC, SqlFunctionCategory.SYSTEM);
+
+  /**
+   * The <code>TRANSLATE(<i>string_expr</i>, <i>search_chars</i>, <i>replacement_chars</i>)</code>
+   * function returns <i>string_expr</i> with all occurrences of each character in
+   * <i>search_chars</i> replaced by its corresponding character in <i>replacement_chars</i>.
+   *
+   * <p>It is not defined in the SQL standard, but occurs in Oracle and PostgreSQL.
+   */
+  @SqlFlavor(flavors = {Flavor.ORACLE, Flavor.POSTGRES})
+  public static final SqlFunction TRANSLATE3 = new SqlTranslate3Function();
+
+  /**
+   * Returns the sql dialect operator table factory, creating it if necessary.
+   */
+  public static synchronized SqlDialectOperatorTableFactory instance() {
+    if (instance == null) {
+      // Creates and initializes this table factory.
+      instance = new SqlDialectOperatorTableFactory();
+      instance.init();
+    }
+    return instance;
+  }
+
+  //~ Methods ----------------------------------------------------------------
+
+  /**
+   * Performs post-constructor initialization of an operator table. It can't
+   * be part of the constructor, because the subclass constructor needs to
+   * complete first.
+   */
+  public final void init() {
+    // Initialize the dialect to SqlOperator mapping.
+    for (Flavor flavor : Flavor.values()) {
+      dialectSqlOperatorTableMapping.put(flavor, new ListSqlOperatorTable());
+    }
+
+    // Use reflection to register the expressions stored in public fields.
+    for (Field field : getClass().getFields()) {
+      try {
+        if (SqlFunction.class.isAssignableFrom(field.getType())) {
+          SqlFunction op = (SqlFunction) field.get(this);
+          if (op != null) {
+            register(op, getSqlDialectsFromField(op.getName(), field));
+          }
+        } else if (
+            SqlOperator.class.isAssignableFrom(field.getType())) {
+          SqlOperator op = (SqlOperator) field.get(this);
+          register(op, getSqlDialectsFromField(op.getName(), field));
+        }
+      } catch (IllegalArgumentException | IllegalAccessException e) {
+        Util.throwIfUnchecked(e.getCause());
+        throw new RuntimeException(e.getCause());
+      }
+    }
+    this.initialized = true;
+  }
+
+  /** Extract supported sql dialects from the field annotation. */
+  private Flavor[] getSqlDialectsFromField(String operatorName, Field field) {
 
 Review comment:
   Should this also rename to "Flavor"?

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