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DataException is thrown if timestamp column is not present in SELECT list #561

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rmoff opened this issue Jan 4, 2019 · 3 comments
Open

DataException is thrown if timestamp column is not present in SELECT list #561

rmoff opened this issue Jan 4, 2019 · 3 comments

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@rmoff
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@rmoff rmoff commented Jan 4, 2019

Given a table:

mysql> describe demo.customers;
+------------+-------------+------+-----+-------------------+-----------------------------------------------+
| Field      | Type        | Null | Key | Default           | Extra                                         |
+------------+-------------+------+-----+-------------------+-----------------------------------------------+
| id         | int(11)     | NO   | PRI | NULL              |                                               |
| first_name | varchar(50) | YES  |     | NULL              |                                               |
| last_name  | varchar(50) | YES  |     | NULL              |                                               |
| email      | varchar(50) | YES  |     | NULL              |                                               |
| gender     | varchar(50) | YES  |     | NULL              |                                               |
| comments   | varchar(90) | YES  |     | NULL              |                                               |
| UPDATE_TS  | timestamp   | YES  |     | CURRENT_TIMESTAMP | DEFAULT_GENERATED on update CURRENT_TIMESTAMP |
+------------+-------------+------+-----+-------------------+-----------------------------------------------+
7 rows in set (0.00 sec)

It is valid to run a query with the predicate column not present in the SELECT criteria:

mysql> SELECT FIRST_NAME, LAST_NAME, GENDER, COMMENTS FROM demo.customers WHERE UPDATE_TS > CURRENT_TIMESTAMP - 100000 ;
+------------+-----------+--------+------------------------------------------------------+
| FIRST_NAME | LAST_NAME | GENDER | COMMENTS                                             |
+------------+-----------+--------+------------------------------------------------------+
| Bibby      | Argabrite | Female | Reactive exuding productivity                        |
| Auberon    | Sulland   | Male   | Organized context-sensitive Graphical User Interface |
| Marv       | Dalrymple | Male   | Versatile didactic pricing structure                 |
| Nolana     | Yeeles    | Female | Adaptive real-time archive                           |
| Modestia   | Coltart   | Female | Reverse-engineered non-volatile success              |
+------------+-----------+--------+------------------------------------------------------+
5 rows in set (0.00 sec)

However the JDBC connector throws an error if the timestamp.column.name is not included in the SELECT.

Config:

curl -X POST http://localhost:8083/connectors -H "Content-Type: application/json" -d '{
        "name": "jdbc_source_mysql_zz",
        "config": {
                "connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
                "connection.url": "jdbc:mysql://mysql:3306/demo",
                "connection.user": "connect_user",
                "connection.password": "asgard",
                "topic.prefix": "mysql-zz-",
                "mode":"timestamp",
                "query":"SELECT FIRST_NAME, LAST_NAME, GENDER, COMMENTS FROM demo.customers",
                "timestamp.column.name": "UPDATE_TS",
                "validate.non.null": false
                }
        }'

Error:

[2019-01-04 17:15:20,005] ERROR WorkerSourceTask{id=jdbc_source_mysql_zz-0} Task threw an uncaught and unrecoverable exception (org.apache.kafka.connect.runtime.WorkerTask)
org.apache.kafka.connect.errors.DataException: UPDATE_TS is not a valid field name
 at org.apache.kafka.connect.data.Struct.lookupField(Struct.java:254)
 at org.apache.kafka.connect.data.Struct.get(Struct.java:74)
 at io.confluent.connect.jdbc.source.TimestampIncrementingCriteria.extractOffsetTimestamp(TimestampIncrementingCriteria.java:211)
 at io.confluent.connect.jdbc.source.TimestampIncrementingCriteria.extractValues(TimestampIncrementingCriteria.java:181)
 at io.confluent.connect.jdbc.source.TimestampIncrementingTableQuerier.extractRecord(TimestampIncrementingTableQuerier.java:185)
 at io.confluent.connect.jdbc.source.JdbcSourceTask.poll(JdbcSourceTask.java:309)
 at org.apache.kafka.connect.runtime.WorkerSourceTask.poll(WorkerSourceTask.java:244)
 at org.apache.kafka.connect.runtime.WorkerSourceTask.execute(WorkerSourceTask.java:220)
 at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:175)
 at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:219)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 at java.lang.Thread.run(Thread.java:748)

The JDBC source connector should not mandate that the field is present, if the query can successfully execute without it.

@rhauch
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@rhauch rhauch commented Jan 4, 2019

@rmoff the timestamp value must be included in the SELECT so that we know the timestamp value of each record. I agree that the error message should be a lot more clear about this requirement.

@aliasbadwolf
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@aliasbadwolf aliasbadwolf commented Mar 6, 2019

@rmoff The final query that connector would fire will be:

SELECT FIRST_NAME, LAST_NAME, GENDER, COMMENTS FROM demo.customers where UPDATE_TS > '<last_saved_offset_timestamp> || 1970-01-01 00:00:00'

The important aspect is that the timestamp column or increment column actually build the WHERE clause. See this class for Timestamp+Incrementing mode (last 3 methods). For other modes there are other classes.

https://github.com/confluentinc/kafka-connect-jdbc/blob/master/src/main/java/io/confluent/connect/jdbc/source/TimestampIncrementingCriteria.java

@dinabogdan
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@dinabogdan dinabogdan commented Dec 11, 2019

Hi! A possible workaround can be to add the timestamp column in the query, but to exclude from the final result using a transform statement like this:

"transforms": "ReplaceField",
"transforms.ReplaceField.type": "org.apache.kafka.connect.transforms.ReplaceField$Value",
"transforms.ReplaceField.blacklist": "created_at"

where created_at is the timestamp column.

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