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From Chandni Singh <chan...@datatorrent.com>
Subject Re: Changes to JdbcOutputOperator
Date Mon, 28 Dec 2015 09:27:42 GMT
Hi Bhupesh,

JDBCPojoOutputOperator was written for a demo and therefore it was marked
Evolving which is why I had mentioned that you should feel free to modify
it.

I think an insert query can be as complex as any other query. It uses
FieldInfo because in the app builder it is easy for the user to provide
that instead of JSON String.

Can you please provide specifics about what it is that you find difficult
to change/implement for providing update/merge/delete support in
JDBCPojoOutputOperator?

Chandni

On Mon, Dec 28, 2015 at 1:09 AM, Bhupesh Chawda <bhupesh@datatorrent.com>
wrote:

> Hi All,
>
> It has been pointed out that adding another class for handling update /
> merge queries would not be a good option.
>
> Here are the current implementation details:
>
>    - We have an existing class: JdbcPOJOOutputOperator which accepts a list
>    of FieldInfo objects. Each element of this list indicates the details
>    (column name, pojo field expression and datatype) of fields that need
> to be
>    inserted. Using this, the operator formulates the insert query in the
> setup
>    method and identifies the sql datatypes of these columns from the
> database
>    using the table name.
>
>
>    - Now, coming to the update / merge feature, it is difficult to
>    formulate the update / merge query in the operator logic due to the
> complex
>    structure of these statements. For this reason, we plan to take a
>    parametrized SQL query from the user. This may look like: *"update table
>    set x = ?, y = ? where z + w > ? and a == 1;"*. Such statements can be
>    accepted from the user in addition to a json string which indicates the
>    details for the parameters: *column name, the pojo expression and the
>    sql data type* of the expression. Note that this information is similar
>    to the FieldInfo object, but is a string which can be configured easily
> by
>    the user. Also note that the data type which is accepted is the SQL data
>    type. Using this info we can populate the parametrized query and run it
>    based on the incoming POJO.
>
> The second approach is able to handle all kinds of queries (insert / update
> / merge / delete). However, since we already have the
> JdbcPOJOOutputOperator, we would like to merge the new functionality into
> the same class.
>
> Here we have the following options:
>
>    1. Change the existing class (JdbcPOJOOutputOperator) to the second
>    approach which is more generic and also handles inserts.
>    2. Add the update/ merge functionality to the existing class without
>    changing the existing functionality. This will have two different ways
> that
>    insert queries may be handled in the operator.
>    3. Add another class which extends from JdbcPOJOOutputOperator and have
>    the update/merge functionality there. (This is not recommended.)
>    4. Any other approach.
>
> Please suggest.
>
> Thanks.
>
> -Bhupesh.
>
>
> On Mon, Dec 14, 2015 at 11:04 AM, Chandni Singh <chandni@datatorrent.com>
> wrote:
>
> > No I don't think we are restricting Malhar to just abstract classes.
> > Whenever they are couple of use cases that we see quite often, we add
> > concrete implementations.
> >
> > For eg. FileLineInputOperator which is a concrete implementation of
> > AbstractFileInputOperator. FSSliceReader is an example as well.
> >
> > In AbstractJdbcOutputOperator case there hasn't been such common
> > insert/update query.
> >
> > Also if you look at the example I provided, it is very simple to provide
> a
> > concrete implementation.
> >
> > If you would like to change JdbcPOJOOutputOperator to work for
> > "UPDATE/MERGE" then please go ahead.
> >
> > Chandni
> >
> > On Sun, Dec 13, 2015 at 8:47 PM, Bhupesh Chawda <bhupesh@datatorrent.com
> >
> > wrote:
> >
> > > I see. So, just to understand more, do we plan to keep Malhar
> restricted
> > to
> > > the base functionality (as in abstract classes)? And put the
> > configuration
> > > aspect / concrete implementations in apps that use these operators?
> > >
> > > Thanks.
> > > Bhupesh
> > >
> > > On Sat, Dec 12, 2015 at 5:43 AM, Chandni Singh <
> chandni@datatorrent.com>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > Here is an example of doing Upsert with JDBC:
> > > >
> > > >
> > >
> >
> https://github.com/chandnisingh/Malhar/blob/examples/apps/jdbc/src/main/java/com/datatorrent/jdbc/JdbcWriter.java
> > > >
> > > > Thanks,
> > > > Chandni
> > > >
> > > > On Fri, Dec 11, 2015 at 11:19 AM, Chandni Singh <
> > chandni@datatorrent.com
> > > >
> > > > wrote:
> > > >
> > > > > The operators are under Malhar/lib/db/jdbc.
> > > > >
> > > > > Here is one of them:
> > > > >
> > > > >
> > > >
> > >
> >
> https://github.com/apache/incubator-apex-malhar/blob/devel-3/library/src/main/java/com/datatorrent/lib/db/jdbc/AbstractJdbcTransactionableOutputOperator.java
> > > > >
> > > > > They work with any kind PreparedStatement - insert or update
> > > > >
> > > > > Chandni
> > > > >
> > > > >
> > > > >
> > > > > On Fri, Dec 11, 2015 at 10:59 AM, Bhupesh Chawda <
> > > > bhupesh@datatorrent.com>
> > > > > wrote:
> > > > >
> > > > >> Hi Chandni,
> > > > >>
> > > > >> I don't see an update query being handled in the operator. Could
> you
> > > > >> please
> > > > >> point me to the appropriate class?
> > > > >> Or did you mean that handling a update query is just a matter
of
> > > > extending
> > > > >> the class and providing a concrete implementation?
> > > > >>
> > > > >> Thanks.
> > > > >> -Bhupesh
> > > > >>
> > > > >> On Fri, Dec 11, 2015 at 10:42 PM, Chandni Singh <
> > > > chandni@datatorrent.com>
> > > > >> wrote:
> > > > >>
> > > > >> > Hi Bhupesh,
> > > > >> >
> > > > >> > The current abstract JDBC Output Operators  in library are
> generic
> > > and
> > > > >> have
> > > > >> > already been used in multiple POCs and applications. In
fact
> this
> > > > >> operator
> > > > >> > has matured through customer use cases. It is not just an
insert
> > > > >> operator.
> > > > >> > We have used it to perform update and inserts.
> > > > >> >
> > > > >> > That said, I don't think it is a good idea to introduce
input
> > format
> > > > in
> > > > >> >  these abstract implementations. It is written to handle
any
> type
> > of
> > > > >> query,
> > > > >> > be it a procedure call (that was an actual customer use
case).
> > > > >> >
> > > > >> > Chandni
> > > > >> >
> > > > >> > On Fri, Dec 11, 2015 at 2:50 AM, Bhupesh Chawda <
> > > > >> bhupesh@datatorrent.com>
> > > > >> > wrote:
> > > > >> >
> > > > >> > > Hi All,
> > > > >> > >
> > > > >> > > We are planning to proceed with the following approach
for
> JDBC
> > > > >> *update*
> > > > >> > > operator:
> > > > >> > >
> > > > >> > >    - *Update Query Configuration*
> > > > >> > >
> > > > >> > >
> > > > >> > >    - Example Update Query: *update tableName set a
= ?**
> where b
> > > = ?
> > > > >> and
> > > > >> > c
> > > > >> > >    > ?;*
> > > > >> > >    - Example JSON input array for parameter instantiations:
> > *[{a,
> > > > >> > >    expression, INTEGER}, {b, expression, VARCHAR},
{c,
> > expression,
> > > > >> > DATE}]*
> > > > >> > >
> > > > >> > > We are also planning to change the JDBC Output Operator
in
> > Malhar
> > > > >> Library
> > > > >> > > which currently does just insert. We plan to make the
input
> > format
> > > > >> > > consistent for both insert and update and hence the
change to
> > the
> > > > >> current
> > > > >> > > way of configuration using JSON. Following would be
the config
> > for
> > > > >> > inserts:
> > > > >> > >
> > > > >> > >    - *Insert Query Configuration*
> > > > >> > >
> > > > >> > >
> > > > >> > >    - Example Insert Query: *insert into tableName values
(?,
> ?,
> > > .. ,
> > > > >> ?);*
> > > > >> > >    - Example JSON input array for parameter instantiations:
> > *[{a,
> > > > >> > >    expression, INTEGER}, {b, expression, VARCHAR},
.. , {c,
> > > > >> expression,
> > > > >> > > DATE}]*
> > > > >> > >
> > > > >> > > Please let us know your thoughts.
> > > > >> > >
> > > > >> > > Thanks.
> > > > >> > >
> > > > >> > > -Bhupesh
> > > > >> > >
> > > > >> > >
> > > > >> > >
> > > > >> > > On Wed, Dec 9, 2015 at 6:38 PM, Bhupesh Chawda <
> > > > >> bhupesh@datatorrent.com>
> > > > >> > > wrote:
> > > > >> > >
> > > > >> > > > Hi All,
> > > > >> > > >
> > > > >> > > > Would it be a good idea to introduce the update
> functionality
> > to
> > > > the
> > > > >> > JDBC
> > > > >> > > > output operator in Apache Apex Malhar library.
> > > > >> > > >
> > > > >> > > > The following are possible approaches:
> > > > >> > > >
> > > > >> > > >    1. Accept a update query from the user with
place holders
> > for
> > > > >> > values.
> > > > >> > > >    Example: *update tableName set a = ?, b = ?
where c = ?
> and
> > > d >
> > > > >> ?*.
> > > > >> > > >    Here "?" will be provided by the user as java
expressions
> > > which
> > > > >> will
> > > > >> > > be
> > > > >> > > >    evaluated from the incoming tuple.
> > > > >> > > >    2. Another option is to accept in some configuration
> format
> > > > >> (json /
> > > > >> > > >    xml) the following and formulate the query
in the
> operator.
> > > > This
> > > > >> can
> > > > >> > > become
> > > > >> > > >    arbitrarily complex.
> > > > >> > > >    1. update clause columns
> > > > >> > > >       2. update clause expressions
> > > > >> > > >       3. where clause columns
> > > > >> > > >       4. where clause expressions
> > > > >> > > >
> > > > >> > > > I am thinking about going ahead with 1. Please
let me know
> if
> > > any
> > > > >> other
> > > > >> > > > option is possible and whether such a functionality
already
> > > exists
> > > > >> in
> > > > >> > > some
> > > > >> > > > other class.
> > > > >> > > >
> > > > >> > > > Thanks.
> > > > >> > > >
> > > > >> > > > -Bhupesh
> > > > >> > > >
> > > > >> > >
> > > > >> >
> > > > >>
> > > > >
> > > > >
> > > >
> > >
> >
>

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