[flink] 02/04: [FLINK-27984][table-common] Introduce FileBasedStatisticsReportableInputFormat interface

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commit 2011a4a9bab947f3819e139faa3341e765a9505d
Author: godfreyhe <go...@163.com>
AuthorDate: Sun Jun 12 16:59:36 2022 +0800

    [FLINK-27984][table-common] Introduce FileBasedStatisticsReportableInputFormat interface
    
    This closes #19939
---
 .../FileBasedStatisticsReportableInputFormat.java  | 53 ++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/connector/format/FileBasedStatisticsReportableInputFormat.java b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/connector/format/FileBasedStatisticsReportableInputFormat.java
new file mode 100644
index 00000000000..4625315b2e8
--- /dev/null
+++ b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/connector/format/FileBasedStatisticsReportableInputFormat.java
@@ -0,0 +1,53 @@
+/*
+ * 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.flink.table.connector.format;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.table.connector.source.abilities.SupportsStatisticReport;
+import org.apache.flink.table.plan.stats.TableStats;
+import org.apache.flink.table.types.DataType;
+
+import java.util.List;
+
+/**
+ * Extension of input format which is able to report estimated statistics for file based connector.
+ *
+ * <p>This interface is used by file-based connectors which should also implement {@link
+ * SupportsStatisticReport}. Since file have different formats, and each format has a different way
+ * of storing and obtaining statistics information. For example: for Parquet and Orc, they both
+ * store the metadata information in the file footer, which including row count, max/min, null
+ * count, etc. While, for csv, there is no other metadata information excluding file size, one
+ * approach to estimate row count is: the entire file size divided by the average length of the
+ * sampled rows.
+ *
+ * <p>Note: This method is called at plan optimization phase, the implementation of this interface
+ * should be as light as possible, but more complete information.
+ */
+@PublicEvolving
+public interface FileBasedStatisticsReportableInputFormat {
+
+    /**
+     * Returns the estimated statistics of this input format.
+     *
+     * @param files The files to be estimated.
+     * @param producedDataType the final output type of the format.
+     */
+    TableStats reportStatistics(List<Path> files, DataType producedDataType);
+}