[
https://issues.apache.org/jira/browse/NIFI-1575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15190099#comment-15190099
]
ASF GitHub Bot commented on NIFI-1575:
--------------------------------------
Github user markap14 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/261#discussion_r55762510
--- 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);
+ }
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSession session) throws ProcessException {
+ FlowFile fileToProcess = null;
+ if (context.hasIncomingConnection()) {
+ fileToProcess = session.get();
+
+ // If we have no FlowFile, and all incoming connections are
self-loops then we can continue on.
+ // However, if we have no FlowFile and we have connections
coming from other Processors, then
+ // we know that we should run only if we have a FlowFile.
+ if (fileToProcess == null && context.hasNonLoopConnection()) {
+ return;
+ }
+ }
+
+ final ProcessorLog logger = getLogger();
+
+ final DBCPService dbcpService =
context.getProperty(DBCP_SERVICE).asControllerService(DBCPService.class);
+ 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 String preProcessStrategy =
context.getProperty(SQL_PREPROCESS_STRATEGY).getValue();
+ final StateManager stateManager = context.getStateManager();
+ final StateMap stateMap;
+ final MaxValueResultSetRowCollector maxValCollector = new
MaxValueResultSetRowCollector(stateManager, preProcessStrategy);
+
+ 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.");
+ context.yield();
+ return;
+ }
+ final String selectQuery = getQuery(tableName, columnNames,
getColumns(maxValueColumnNames), stateMap, preProcessStrategy);
+ final StopWatch stopWatch = new StopWatch(true);
+
+ 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
+
+ final LongHolder nrOfRows = new LongHolder(0L);
+ if (fileToProcess == null) {
+ fileToProcess = session.create();
+ }
+ fileToProcess = session.write(fileToProcess, new
OutputStreamCallback() {
+ @Override
+ public void process(final OutputStream out) throws
IOException {
+ try {
+ logger.debug("Executing query {}", new
Object[]{selectQuery});
+ final ResultSet resultSet =
st.executeQuery(selectQuery);
+ // Max values will be updated in the State by the
callback
+
nrOfRows.set(JdbcCommon.convertToAvroStream(resultSet, out, tableName,
maxValCollector));
+ } catch (final SQLException e) {
+ throw new ProcessException(e);
+ }
+ }
+ });
+
+ if (nrOfRows.get() > 0) {
+ // set attribute how many rows were selected
+ fileToProcess = session.putAttribute(fileToProcess,
RESULT_ROW_COUNT, nrOfRows.get().toString());
+
+ logger.info("{} contains {} Avro records; transferring to
'success'",
+ new Object[]{fileToProcess, nrOfRows.get()});
+
session.getProvenanceReporter().modifyContent(fileToProcess, "Retrieved " +
nrOfRows.get() + " rows",
+ stopWatch.getElapsed(TimeUnit.MILLISECONDS));
+ session.transfer(fileToProcess, REL_SUCCESS);
+ } else {
+ // If there were no rows returned, don't send the flowfile
+ session.remove(fileToProcess);
+ context.yield();
+ }
+
+ } catch (final ProcessException | SQLException e) {
+ if (fileToProcess == null) {
+ // This can happen if any exceptions occur while setting
up the connection, statement, etc.
+ logger.error("Unable to execute SQL select query {} due to
{}. No FlowFile to route to failure",
+ new Object[]{selectQuery, e});
+ context.yield();
+ } else {
+ if (context.hasIncomingConnection()) {
+ logger.error("Unable to execute SQL select query {}
for {} due to {}; routing to failure",
+ new Object[]{selectQuery, fileToProcess, e});
+ fileToProcess = session.penalize(fileToProcess);
+ } else {
+ logger.error("Unable to execute SQL select query {}
due to {}; routing to failure",
+ new Object[]{selectQuery, e});
+ context.yield();
+ }
+ session.transfer(fileToProcess, REL_FAILURE);
+ }
+ }
+ }
+
+ protected List<String> getColumns(String commaSeparatedColumnList) {
+ if (StringUtils.isEmpty(commaSeparatedColumnList)) {
+ return Collections.emptyList();
+ }
+ final String[] columns = commaSeparatedColumnList.split(",");
+ final List<String> columnList = new ArrayList<>(columns.length);
+ for (String column : columns) {
+ if (column != null) {
+ String trimmedColumn = column.trim();
+ if (!StringUtils.isEmpty(trimmedColumn)) {
+ columnList.add(trimmedColumn);
+ }
+ }
+ }
+ return columnList;
+ }
+
+ protected String getQuery(String tableName, String columnNames,
List<String> maxValColumnNames,
+ StateMap stateMap, String
preProcessStrategy) {
+ if (StringUtils.isEmpty(tableName)) {
+ throw new IllegalArgumentException("Table name must be
specified");
+ }
+ final StringBuilder query = new
StringBuilder(getSelectFromClause(tableName, columnNames));
+
+ // Check state map for last max values
+ if (stateMap != null && stateMap.getVersion() != -1 &&
maxValColumnNames != null) {
+ Map<String, String> stateProperties = stateMap.toMap();
+ List<String> whereClauses = new
ArrayList<>(maxValColumnNames.size());
+ for (String colName : maxValColumnNames) {
+ String maxValue =
stateProperties.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
+ whereClauses.add(colName + " > " +
getLiteralByType(type, maxValue, preProcessStrategy));
+ }
+ }
+ if (!whereClauses.isEmpty()) {
+ query.append(" WHERE ");
+ query.append(StringUtils.join(whereClauses, " AND "));
+ }
+ }
+
+ return query.toString();
+ }
+
+ /**
+ * Returns a basic SELECT ... FROM clause with the given column names
and table name. If no column names are found,
+ * the wildcard (*) is used to select all columns.
+ *
+ * @param tableName The name of the table to select from
+ * @param columnNames A comma-separated list of column names to select
from the table
+ * @return A SQL select statement representing a query of the given
column names from the given table
+ */
+ protected StringBuilder getSelectFromClause(String tableName, String
columnNames) {
+ final StringBuilder query = new StringBuilder("SELECT ");
+ if (StringUtils.isEmpty(columnNames) ||
columnNames.trim().equals("*")) {
+ query.append("*");
+ } else {
+ query.append(columnNames);
+ }
+ query.append(" FROM ");
+ query.append(tableName);
+ return query;
+ }
+
+ /**
+ * Returns a SQL literal for the given value based on its type. For
example, values of character type need to be enclosed
+ * in single quotes, whereas values of numeric type should not be.
+ *
+ * @param type The JDBC type for the desired literal
+ * @param value The value to be converted to a SQL literal
+ * @return A String representing the given value as a literal of the
given type
+ */
+ protected String getLiteralByType(int type, String value, String
preProcessStrategy) {
+ // Format value based on column type. For example, strings and
timestamps need to be quoted
+ switch (type) {
+ // For string-represented values, put in single quotes
+ case CHAR:
+ case LONGNVARCHAR:
+ case LONGVARCHAR:
+ case NCHAR:
+ case NVARCHAR:
+ case VARCHAR:
+ case ROWID:
+ case DATE:
+ case TIME:
+ return "'" + value + "'";
+ case TIMESTAMP:
+ // Timestamp literals in Oracle need to be cast with
TO_DATE
+ if ("Oracle".equals(preProcessStrategy)) {
+ return "to_date('" + value + "', 'yyyy-mm-dd
HH24:MI:SS')";
+ } else {
+ return "'" + value + "'";
+ }
+ // Else leave as is (numeric types, e.g.)
+ default:
+ return value;
+ }
+ }
+
+ protected class MaxValueResultSetRowCollector implements
JdbcCommon.ResultSetRowCallback {
+ StateManager stateManager;
+ String preProcessStrategy;
+
+ public MaxValueResultSetRowCollector(StateManager stateManager,
String preProcessStrategy) {
+ this.stateManager = stateManager;
+ this.preProcessStrategy = preProcessStrategy;
+ }
+
+ @Override
+ public void processRow(ResultSet resultSet) throws IOException {
+ if (resultSet == null) {
+ return;
+ }
+ try {
+ // Iterate over the row, check-and-set max values
+ StateMap stateMap = stateManager.getState(Scope.CLUSTER);
+ Map<String, String> oldColMap = stateMap.toMap();
+ Map<String, String> newColMap = new
HashMap<>(oldColMap.size());
+ newColMap.putAll(oldColMap);
+ final ResultSetMetaData meta = resultSet.getMetaData();
+ final int nrOfColumns = meta.getColumnCount();
+ if (nrOfColumns > 0) {
+ for (int i = 1; i <= nrOfColumns; i++) {
+ String colName =
meta.getColumnName(i).toLowerCase();
+ Integer type = columnTypeMap.get(colName);
+ // Skip any columns we're not keeping track of or
whose value is null
+ if (type == null || resultSet.getObject(i) ==
null) {
+ continue;
+ }
+ String maxValueString = oldColMap.get(colName);
+ switch (type) {
+ case CHAR:
+ case LONGNVARCHAR:
+ case LONGVARCHAR:
+ case NCHAR:
+ case NVARCHAR:
+ case VARCHAR:
+ case ROWID:
+ String colStringValue =
resultSet.getString(i);
+ if (maxValueString == null ||
colStringValue.compareTo(maxValueString) > 0) {
+ newColMap.put(colName, colStringValue);
+ }
+ break;
+
+ case INTEGER:
+ case SMALLINT:
+ case TINYINT:
+ Integer colIntValue = resultSet.getInt(i);
+ Integer maxIntValue = null;
+ if (maxValueString != null) {
+ maxIntValue =
Integer.valueOf(maxValueString);
+ }
+ if (maxIntValue == null || colIntValue >
maxIntValue) {
+ newColMap.put(colName,
colIntValue.toString());
+ }
+ break;
+
+ case BIGINT:
+ Long colLongValue = resultSet.getLong(i);
+ Long maxLongValue = null;
+ if (maxValueString != null) {
+ maxLongValue =
Long.valueOf(maxValueString);
+ }
+ if (maxLongValue == null || colLongValue >
maxLongValue) {
+ newColMap.put(colName,
colLongValue.toString());
+ }
+ break;
+
+ case FLOAT:
+ case REAL:
+ case DOUBLE:
+ Double colDoubleValue =
resultSet.getDouble(i);
+ Double maxDoubleValue = null;
+ if (maxValueString != null) {
+ maxDoubleValue =
Double.valueOf(maxValueString);
+ }
+ if (maxDoubleValue == null ||
colDoubleValue > maxDoubleValue) {
+ newColMap.put(colName,
colDoubleValue.toString());
+ }
+ break;
+
+ case DECIMAL:
+ case NUMERIC:
+ BigDecimal colBigDecimalValue =
resultSet.getBigDecimal(i);
+ BigDecimal maxBigDecimalValue = null;
+ if (maxValueString != null) {
+ DecimalFormat df = new DecimalFormat();
+ df.setParseBigDecimal(true);
+ maxBigDecimalValue = (BigDecimal)
df.parse(maxValueString);
+ }
+ if (maxBigDecimalValue == null ||
colBigDecimalValue.compareTo(maxBigDecimalValue) > 0) {
+ newColMap.put(colName,
colBigDecimalValue.toString());
+ }
+ break;
+
+ case DATE:
+ Date rawColDateValue =
resultSet.getDate(i);
+ java.sql.Date colDateValue = new
java.sql.Date(rawColDateValue.getTime());
+ java.sql.Date maxDateValue = null;
+ if (maxValueString != null) {
+ maxDateValue =
java.sql.Date.valueOf(maxValueString);
+ }
+ if (maxDateValue == null ||
colDateValue.after(maxDateValue)) {
+ newColMap.put(colName,
colDateValue.toString());
+ }
+ break;
+
+ case TIME:
+ Date rawColTimeValue =
resultSet.getDate(i);
+ java.sql.Time colTimeValue = new
java.sql.Time(rawColTimeValue.getTime());
+ java.sql.Time maxTimeValue = null;
+ if (maxValueString != null) {
+ maxTimeValue =
java.sql.Time.valueOf(maxValueString);
+ }
+ if (maxTimeValue == null ||
colTimeValue.after(maxTimeValue)) {
+ newColMap.put(colName,
colTimeValue.toString());
+ }
+ break;
+
+ case TIMESTAMP:
+ if ("Oracle".equals(preProcessStrategy)) {
--- End diff --
Would again make a static final member variable out of this
> Add ability to query DB table using "last value" from column
> ------------------------------------------------------------
>
> Key: NIFI-1575
> URL: https://issues.apache.org/jira/browse/NIFI-1575
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Extensions
> Reporter: Matt Burgess
> Assignee: Matt Burgess
> Fix For: 0.6.0
>
>
> It would be a useful feature for a processor to be able to query from a
> database table for only those records that have are added/available since the
> last time the query was executed. For example, if the processor could keep
> the max value of a timestamp column for the last result set returned, the
> next time the query was issued, it could use that timestamp value and column
> to only return records whose timestamps were greater than "the last time".
> This shouldn't be limited to timestamps of course; it would be useful for any
> strictly-increasing value (like primary key ID) but would be up to the user
> to select the table and column. The processor would simply keep the state for
> the specified column's max value.
> Proposed is a "QueryDBTable" processor which would have a properties to
> specify the table name and the column in the table for which to keep state
> information about the last maximum value retrieved. Subsequent queries of the
> table use this value to filter for rows whose value for the specified column
> are greater than the "last maximum value". Upon each successful query, the
> "last maximum value" is updated.
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