Github user markap14 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/261#discussion_r55759929
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/QueryDatabaseTable.java
---
@@ -0,0 +1,607 @@
+/*
+ * 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.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.ProcessorLog;
+import org.apache.nifi.processor.AbstractProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.io.OutputStreamCallback;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.processors.standard.util.JdbcCommon;
+import org.apache.nifi.util.LongHolder;
+import org.apache.nifi.util.StopWatch;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.math.BigDecimal;
+import java.sql.Connection;
+import java.sql.Date;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.sql.Timestamp;
+import java.text.DecimalFormat;
+import java.text.ParseException;
+import java.util.ArrayList;
+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;
+
+import static java.sql.Types.ARRAY;
+import static java.sql.Types.BIGINT;
+import static java.sql.Types.BINARY;
+import static java.sql.Types.BIT;
+import static java.sql.Types.BLOB;
+import static java.sql.Types.BOOLEAN;
+import static java.sql.Types.CHAR;
+import static java.sql.Types.CLOB;
+import static java.sql.Types.DATE;
+import static java.sql.Types.DECIMAL;
+import static java.sql.Types.DOUBLE;
+import static java.sql.Types.FLOAT;
+import static java.sql.Types.INTEGER;
+import static java.sql.Types.LONGNVARCHAR;
+import static java.sql.Types.LONGVARBINARY;
+import static java.sql.Types.LONGVARCHAR;
+import static java.sql.Types.NCHAR;
+import static java.sql.Types.NUMERIC;
+import static java.sql.Types.NVARCHAR;
+import static java.sql.Types.REAL;
+import static java.sql.Types.ROWID;
+import static java.sql.Types.SMALLINT;
+import static java.sql.Types.TIME;
+import static java.sql.Types.TIMESTAMP;
+import static java.sql.Types.TINYINT;
+import static java.sql.Types.VARBINARY;
+import static java.sql.Types.VARCHAR;
+
+@EventDriven
+@InputRequirement(Requirement.INPUT_ALLOWED)
+@Tags({"sql", "select", "jdbc", "query", "database"})
+@CapabilityDescription("Execute provided SQL select query. Query result
will be converted to Avro format."
+ + " Streaming is used so arbitrarily large result sets are
supported. This processor can be scheduled to run on "
+ + "a timer, or cron expression, using the standard scheduling
methods, or it can be triggered by an incoming FlowFile. "
+ + "If it is triggered by an incoming FlowFile, then attributes of
that FlowFile will be available when evaluating the "
+ + "select query. FlowFile attribute 'querydbtable.row.count'
indicates how many rows were selected.")
+@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 QueryDatabaseTable extends AbstractProcessor {
+
+ public static final String RESULT_ROW_COUNT = "querydbtable.row.count";
+
+ // Relationships
+ public static final Relationship REL_SUCCESS = new
Relationship.Builder()
+ .name("success")
+ .description("Successfully created FlowFile from SQL query
result set.")
+ .build();
+ public static final Relationship REL_FAILURE = new
Relationship.Builder()
+ .name("failure")
+ .description("SQL query execution failed. Incoming FlowFile
will be penalized and routed to this relationship.")
+ .build();
+ private final Set<Relationship> relationships;
+
+ public static final PropertyDescriptor DBCP_SERVICE = new
PropertyDescriptor.Builder()
+ .name("Database Connection Pooling Service")
+ .description("The Controller Service that is used to obtain a
connection to the database.")
+ .required(true)
+ .identifiesControllerService(DBCPService.class)
+ .build();
+
+ public static final PropertyDescriptor TABLE_NAME = new
PropertyDescriptor.Builder()
+ .name("Table Name")
+ .description("The name of the database table to be queried.")
+ .required(true)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor COLUMN_NAMES = new
PropertyDescriptor.Builder()
+ .name("Columns to return")
+ .description("A comma-separated list of column names to be
used in the query. If your database requires "
+ + "special treatment of the names (quoting, e.g.),
each name should include such treatment. If no "
+ + "column names are supplied, all columns in the
specified table will be returned.")
+ .required(false)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor MAX_VALUE_COLUMN_NAMES = new
PropertyDescriptor.Builder()
+ .name("Maximum-value Columns")
+ .description("A comma-separated list of column names. The
processor will keep track of the maximum value "
+ + "for each column that has been returned since the
processor started running. This can be used to "
+ + "retrieve only those rows that have been
added/updated since the last retrieval. Note that some "
+ + "JDBC types such as bit/boolean are not conducive to
maintaining maximum value, so columns of these "
+ + "types should not be listed in this property, and
will result in error(s) during processing.")
+ .required(false)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor QUERY_TIMEOUT = new
PropertyDescriptor.Builder()
+ .name("Max Wait Time")
+ .description("The maximum amount of time allowed for a running
SQL select query "
+ + ", zero means there is no limit. Max time less than
1 second will be equal to zero.")
+ .defaultValue("0 seconds")
+ .required(true)
+ .addValidator(StandardValidators.TIME_PERIOD_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor SQL_PREPROCESS_STRATEGY = new
PropertyDescriptor.Builder()
+ .name("SQL Pre-processing Strategy")
+ .description("The strategy to employ when generating the SQL
for querying the table. A strategy may include "
+ + "custom or database-specific code, such as the
treatment of time/date formats.")
+ .defaultValue("0 seconds")
+ .required(true)
+ .allowableValues("None", "Oracle")
+ .defaultValue("None")
+ .build();
+
+
+ private final List<PropertyDescriptor> propDescriptors;
+
+ protected final Map<String, Integer> columnTypeMap = new HashMap<>();
+
+ public QueryDatabaseTable() {
+ final Set<Relationship> r = new HashSet<>();
+ r.add(REL_SUCCESS);
+ r.add(REL_FAILURE);
+ relationships = Collections.unmodifiableSet(r);
+
+ final List<PropertyDescriptor> pds = new ArrayList<>();
+ pds.add(DBCP_SERVICE);
+ pds.add(TABLE_NAME);
+ pds.add(COLUMN_NAMES);
+ pds.add(MAX_VALUE_COLUMN_NAMES);
+ pds.add(QUERY_TIMEOUT);
+ pds.add(SQL_PREPROCESS_STRATEGY);
+ 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) {
+ // Try to fill the columnTypeMap with the types of the desired
max-value columns
+ final DBCPService dbcpService =
context.getProperty(DBCP_SERVICE).asControllerService(DBCPService.class);
+ final String tableName =
context.getProperty(TABLE_NAME).getValue();
+ final String maxValueColumnNames =
context.getProperty(MAX_VALUE_COLUMN_NAMES).getValue();
+
+ try (final Connection con = dbcpService.getConnection();
+ final Statement st = con.createStatement()) {
+
+ // Try a query that returns no rows, for the purposes of
getting metadata about the columns. It is possible
+ // to use DatabaseMetaData.getColumns(), but not all drivers
support this, notably the schema-on-read
+ // approach as in Apache Drill
+ String query = getSelectFromClause(tableName,
maxValueColumnNames).append(" WHERE 1 = 0").toString();
+ ResultSet resultSet = st.executeQuery(query);
+ ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
+ int numCols = resultSetMetaData.getColumnCount();
+ if (numCols > 0) {
+ columnTypeMap.clear();
+ for (int i = 1; i <= numCols; i++) {
+ String colName =
resultSetMetaData.getColumnName(i).toLowerCase();
+ int colType = resultSetMetaData.getColumnType(i);
+ columnTypeMap.put(colName, colType);
+ }
+
+ } else {
+ throw new ProcessException("No columns found in table from
those specified: " + maxValueColumnNames);
+ }
+
+ } catch (SQLException e) {
+ throw new ProcessException(e);
--- End diff --
Why catch the SQLException and wrap it? Would recommend just allowing the
SQLException to fly -- or, better yet, throw a ProcessException that wraps
SQLException but provides more information about what's going on, such as: new
ProcessException("Unable to communicate with database in order to determine
column types", e);
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