Github user JPercivall commented on a diff in the pull request:
https://github.com/apache/nifi/pull/645#discussion_r71073752
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/GenerateTableFetch.java
---
@@ -0,0 +1,254 @@
+/*
+ * 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.nifi.processors.standard;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.nifi.annotation.behavior.EventDriven;
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
+import org.apache.nifi.annotation.behavior.Stateful;
+import org.apache.nifi.annotation.behavior.WritesAttribute;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.SeeAlso;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.state.Scope;
+import org.apache.nifi.components.state.StateManager;
+import org.apache.nifi.components.state.StateMap;
+import org.apache.nifi.dbcp.DBCPService;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.logging.ComponentLog;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.ProcessSessionFactory;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.processors.standard.db.DatabaseAdapter;
+
+import java.io.IOException;
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.text.ParseException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+
+@EventDriven
+@InputRequirement(Requirement.INPUT_FORBIDDEN)
+@Tags({"sql", "select", "jdbc", "query", "database", "fetch", "generate"})
+@SeeAlso(QueryDatabaseTable.class)
+@CapabilityDescription("Generates SQL select queries that fetch \"pages\"
of rows from a table. The partition size property, along with the table's row
count, "
+ + "determine the size and number of pages and generated FlowFiles.
In addition, incremental fetching can be achieved by setting Maximum-Value
Columns, "
+ + "which causes the processor to track the columns' maximum
values, thus only fetching rows whose columns' values exceed the observed
maximums.")
+@Stateful(scopes = Scope.CLUSTER, description = "After performing a query
on the specified table, the maximum values for "
+ + "the specified column(s) will be retained for use in future
executions of the query. This allows the Processor "
+ + "to fetch only those records that have max values greater than
the retained values. This can be used for "
+ + "incremental fetching, fetching of newly added rows, etc. To
clear the maximum values, clear the state of the processor "
+ + "per the State Management documentation")
+@WritesAttribute(attribute = "querydbtable.row.count")
+public class GenerateTableFetch extends AbstractDatabaseFetchProcessor {
+
+
+ public static final PropertyDescriptor PARTITION_SIZE = new
PropertyDescriptor.Builder()
+ .name("gen-table-fetch-partition-size")
+ .displayName("Partition Size")
+ .description("The number of result rows to be fetched by each
generated SQL statement. The total number of rows in "
+ + "the table divided by the partition size gives the
number of SQL statements (i.e. FlowFiles) generated. A "
+ + "value of zero indicates that a single FlowFile is
to be generated whose SQL statement will fetch all rows "
+ + "in the table.")
+ .defaultValue("10000")
+ .required(true)
+ .expressionLanguageSupported(false)
+
.addValidator(StandardValidators.NON_NEGATIVE_INTEGER_VALIDATOR)
+ .build();
+
+ public GenerateTableFetch() {
+ final Set<Relationship> r = new HashSet<>();
+ r.add(REL_SUCCESS);
+ relationships = Collections.unmodifiableSet(r);
+
+ final List<PropertyDescriptor> pds = new ArrayList<>();
+ pds.add(DBCP_SERVICE);
+ pds.add(DB_TYPE);
+ pds.add(TABLE_NAME);
+ pds.add(COLUMN_NAMES);
+ pds.add(MAX_VALUE_COLUMN_NAMES);
+ pds.add(QUERY_TIMEOUT);
+ pds.add(PARTITION_SIZE);
+ propDescriptors = Collections.unmodifiableList(pds);
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+ return relationships;
+ }
+
+ @Override
+ protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+ return propDescriptors;
+ }
+
+ @OnScheduled
+ public void setup(final ProcessContext context) {
+ super.setup(context);
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSessionFactory sessionFactory) throws ProcessException {
+ ProcessSession session = sessionFactory.createSession();
+ final ComponentLog logger = getLogger();
+
+ final DBCPService dbcpService =
context.getProperty(DBCP_SERVICE).asControllerService(DBCPService.class);
+ final DatabaseAdapter dbAdapter =
dbAdapters.get(context.getProperty(DB_TYPE).getValue());
+ final String tableName =
context.getProperty(TABLE_NAME).getValue();
+ final String columnNames =
context.getProperty(COLUMN_NAMES).getValue();
+ final String maxValueColumnNames =
context.getProperty(MAX_VALUE_COLUMN_NAMES).getValue();
+ final int partitionSize =
context.getProperty(PARTITION_SIZE).asInteger();
+
+ final StateManager stateManager = context.getStateManager();
+ final StateMap stateMap;
+
+ try {
+ stateMap = stateManager.getState(Scope.CLUSTER);
+ } catch (final IOException ioe) {
+ getLogger().error("Failed to retrieve observed maximum values
from the State Manager. Will not perform "
+ + "query until this is accomplished.", ioe);
+ context.yield();
+ return;
+ }
+ // Make a mutable copy of the current state property map. This
will be updated by the result row callback, and eventually
+ // set as the current state map (after the session has been
committed)
+ final Map<String, String> statePropertyMap = new
HashMap<>(stateMap.toMap());
+
+ // Build a WHERE clause with maximum-value columns (if they
exist), and a list of column names that will contain MAX(<column>) aliases. The
+ // executed SQL query will retrieve the count of all records after
the filter(s) have been applied, as well as the new maximum values for the
+ // specified columns. This allows the processor to generate the
correctly partitioned SQL statements as well as to update the state with the
+ // latest observed maximum values.
+ String whereClause = null;
+ List<String> maxValueColumnNameList =
StringUtils.isEmpty(maxValueColumnNames)
+ ? new ArrayList<>(0)
+ : Arrays.asList(maxValueColumnNames.split("\\s*,\\s*"));
+ List<String> maxValueClauses = new
ArrayList<>(maxValueColumnNameList.size());
+
+ String columnsClause = null;
+ List<String> maxValueSelectColumns = new
ArrayList<>(maxValueColumnNameList.size() + 1);
+ maxValueSelectColumns.add("COUNT(*)");
+
+ // For each maximum-value column, get a WHERE filter and a
MAX(column) alias
+ maxValueColumnNameList.forEach(colName -> {
+ maxValueSelectColumns.add("MAX(" + colName + ") " + colName);
+ String maxValue = statePropertyMap.get(colName.toLowerCase());
+ if (!StringUtils.isEmpty(maxValue)) {
+ Integer type = columnTypeMap.get(colName.toLowerCase());
+ if (type == null) {
+ // This shouldn't happen as we are populating
columnTypeMap when the processor is scheduled.
+ throw new IllegalArgumentException("No column type
found for: " + colName);
+ }
+ // Add a condition for the WHERE clause
+ maxValueClauses.add(colName + " > " +
getLiteralByType(type, maxValue, dbAdapter.getName()));
+ }
+ });
+
+ whereClause = StringUtils.join(maxValueClauses, " AND ");
+ columnsClause = StringUtils.join(maxValueSelectColumns, ", ");
+
+ // Build a SELECT query with maximum-value columns (if present)
+ final String selectQuery = dbAdapter.getSelectStatement(tableName,
columnsClause, whereClause, null, null, null);
+
+ try (final Connection con = dbcpService.getConnection();
+ final Statement st = con.createStatement()) {
+
+ final Integer queryTimeout =
context.getProperty(QUERY_TIMEOUT).asTimePeriod(TimeUnit.SECONDS).intValue();
+ st.setQueryTimeout(queryTimeout); // timeout in seconds
+
+ logger.debug("Executing {}", new Object[]{selectQuery});
+ ResultSet resultSet = st.executeQuery(selectQuery);
+ if (resultSet.next()) {
+ // Total row count is in the first column
+ int rowCount = resultSet.getInt(1);
+
+ // Update the state map with the newly-observed maximum
values
+ ResultSetMetaData rsmd = resultSet.getMetaData();
+ for (int i = 2; i <= rsmd.getColumnCount(); i++) {
+ String resultColumnName =
rsmd.getColumnName(i).toLowerCase();
+ int type = rsmd.getColumnType(i);
+ try {
+ String newMaxValue = getMaxValueFromRow(resultSet,
i, type, statePropertyMap.get(resultColumnName.toLowerCase()),
dbAdapter.getName());
+ if (newMaxValue != null) {
+ statePropertyMap.put(resultColumnName,
newMaxValue);
+ }
+ } catch (ParseException | IOException pie) {
+ // Fail the whole thing here before we start
creating flow files and such
+ throw new ProcessException(pie);
+ }
+ }
+
+ final int numberOfFetches = (partitionSize == 0) ?
rowCount : (rowCount / partitionSize) + (rowCount % partitionSize == 0 ? 0 : 1);
+
+ // Generate SQL statements to read "pages" of data
+ for (int i = 0; i < numberOfFetches; i++) {
+ FlowFile sqlFlowFile = null;
+ try {
+ Integer limit = partitionSize == 0 ? null :
partitionSize;
+ Integer offset = partitionSize == 0 ? null : i *
partitionSize;
+ final String query =
dbAdapter.getSelectStatement(tableName, columnNames,
StringUtils.join(maxValueClauses, " AND "), null, limit, offset);
+ sqlFlowFile = session.create();
+ sqlFlowFile = session.write(sqlFlowFile, out -> {
+ out.write(query.getBytes());
+ });
+ session.transfer(sqlFlowFile, REL_SUCCESS);
+
+ } catch (Exception e) {
+ logger.error("Error while generating SQL
statement", e);
+ if (sqlFlowFile != null) {
+ session.remove(sqlFlowFile);
+ }
+ }
+ }
+
+ } else {
+ // Something is very wrong here, one row (even if count is
zero) should be returned
+ throw new SQLException("No rows returned from metadata
query: " + selectQuery);
+ }
+
+
+ session.commit();
+ try {
+ // Update the state
+ stateManager.setState(statePropertyMap, Scope.CLUSTER);
+ } catch (IOException ioe) {
+ getLogger().error("{} failed to update State Manager,
observed maximum values will not be recorded", new Object[]{this, ioe});
--- End diff --
This should re-enforce to the user that sql statement will be duplicated.
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