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I’m attempting to create a stream using JDBCInputFormat. Objective is to convert each record into a tuple and then serialize for input into a Kafka topic. Here’s what I have so far.
``` val env = StreamExecutionEnvironment.getExecutionEnvironment
val inputFormat = JDBCInputFormat.buildJDBCInputFormat() .setDrivername("org.postgresql.Driver") .setDBUrl("jdbc:postgresql:test") .setQuery("select name from persons") .finish()
val stream : DataStream[Tuple1[String]] = env.createInput(...) ```
I think this is essentially what I want to do. It would be nice if I could return tuples of arbitrary length, but reading the code suggests I have to commit to a defined arity. So I have some questions.
1. Is there a better way to read from a database (i.e., defining my own `InputFormat` using Slick)? 2. To get the above example working, what should I supply to `createInput`?
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you can always create your own
InputFormat, but there is no AbstractJDBCInputFormat if that's
what you were looking for.
When you say arbitrary tuple size, do you mean a) a size greater
than 25, or b) tuples of different sizes?
If a) unless you are fine with using nested tuples you won't get
around the tuple size limitation. Since the user has to be aware
of the nesting (since the fields can be accessed directly via
tuple.f0 etc), this can't really be done in a general-purpose
fashion.
If b) this will straight-up not work with tuples.
You could use POJO's though. then you could also group by column
names.
I'm not sure about Scala, but in the Java Stream API you can pass
the InputFormat and the TypeInformation into createInput.
I've recently did a prototype where the input type is determined
automatically by querying the database. If this is a problem for
you feel free to ping me.
On 09.03.2016 03:17, Prez Cannady wrote:
I’m attempting to create a stream using
JDBCInputFormat. Objective is to convert each record into a
tuple and then serialize for input into a Kafka topic. Here’s
what I have so far.
```
val env =
StreamExecutionEnvironment.getExecutionEnvironment
val inputFormat =
JDBCInputFormat.buildJDBCInputFormat()
.setDrivername("org.postgresql.Driver")
.setDBUrl("jdbc:postgresql:test")
.setQuery("select name from persons")
.finish()
val stream : DataStream[Tuple1[String]] =
env.createInput(...)
```
I think this is essentially what I want to do. It
would be nice if I could return tuples of arbitrary length, but
reading the code suggests I have to commit to a defined arity.
So I have some questions.
1. Is there a better way to read from a database
(i.e., defining my own `InputFormat` using Slick)?
2. To get the above example working, what should I
supply to `createInput`?
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I suspected as much (the tuple size limitation). Creating my own InputFormat seems to be the best solution, but before i go down that rabbit hole I wanted to see at least a semi-trivial working example of JDBCInputFormat with Scala 2.11.
I’d appreciate a look at that prototype if its publicly available (even if it is Java). I might glean a hint from it.
you can always create your own
InputFormat, but there is no AbstractJDBCInputFormat if that's
what you were looking for.
When you say arbitrary tuple size, do you mean a) a size greater
than 25, or b) tuples of different sizes?
If a) unless you are fine with using nested tuples you won't get
around the tuple size limitation. Since the user has to be aware
of the nesting (since the fields can be accessed directly via
tuple.f0 etc), this can't really be done in a general-purpose
fashion.
If b) this will straight-up not work with tuples.
You could use POJO's though. then you could also group by column
names.
I'm not sure about Scala, but in the Java Stream API you can pass
the InputFormat and the TypeInformation into createInput.
I've recently did a prototype where the input type is determined
automatically by querying the database. If this is a problem for
you feel free to ping me.
On 09.03.2016 03:17, Prez Cannady wrote:
I’m attempting to create a stream using
JDBCInputFormat. Objective is to convert each record into a
tuple and then serialize for input into a Kafka topic. Here’s
what I have so far.
```
val env =
StreamExecutionEnvironment.getExecutionEnvironment
val inputFormat =
JDBCInputFormat.buildJDBCInputFormat()
.setDrivername("org.postgresql.Driver")
.setDBUrl("jdbc:postgresql:test")
.setQuery("select name from persons")
.finish()
val stream : DataStream[Tuple1[String]] =
env.createInput(...)
```
I think this is essentially what I want to do. It
would be nice if I could return tuples of arbitrary length, but
reading the code suggests I have to commit to a defined arity.
So I have some questions.
1. Is there a better way to read from a database
(i.e., defining my own `InputFormat` using Slick)?
2. To get the above example working, what should I
supply to `createInput`?
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now that i look back to my mail i may
have given you the wrong idea about the prototype; to make sure we
are on the same page:
the only thing it enables is using the JDBCInputFormat without
providing a separate TypeInformation. Still works with tuples, not
POJO's.
you can find the prototype here:
https://github.com/zentol/flink/tree/3445_jdbc
The JDBCInputFormat there implements ResultTypeQueryable. WIthin
getProducedType it executes a dummy query, reads the
ResultSetMetaData and generates a TypeInfo from it.
On 09.03.2016 12:46, Prez Cannady wrote:
I suspected as much (the tuple size limitation).
Creating my own InputFormat seems to be the best solution, but
before i go down that rabbit hole I wanted to see at least a
semi-trivial working example of JDBCInputFormat with Scala 2.11.
I’d appreciate a look at that prototype if its
publicly available (even if it is Java). I might glean a hint
from it.
you can always create your
own InputFormat, but there is no AbstractJDBCInputFormat
if that's what you were looking for.
When you say arbitrary tuple size, do you mean a) a size
greater than 25, or b) tuples of different sizes?
If a) unless you are fine with using nested tuples you
won't get around the tuple size limitation. Since the
user has to be aware of the nesting (since the fields
can be accessed directly via tuple.f0 etc), this can't
really be done in a general-purpose fashion.
If b) this will straight-up not work with tuples.
You could use POJO's though. then you could also group
by column names.
I'm not sure about Scala, but in the Java Stream API you
can pass the InputFormat and the TypeInformation into
createInput.
I've recently did a prototype where the input type is
determined automatically by querying the database. If
this is a problem for you feel free to ping me.
On 09.03.2016 03:17, Prez Cannady wrote:
I’m attempting to create a stream using
JDBCInputFormat. Objective is to convert each record
into a tuple and then serialize for input into a Kafka
topic. Here’s what I have so far.
```
val env =
StreamExecutionEnvironment.getExecutionEnvironment
val inputFormat =
JDBCInputFormat.buildJDBCInputFormat()
.setDrivername("org.postgresql.Driver")
.setDBUrl("jdbc:postgresql:test")
.setQuery("select name from
persons")
.finish()
val stream : DataStream[Tuple1[String]]
= env.createInput(...)
```
I think this is essentially what I want to
do. It would be nice if I could return tuples of
arbitrary length, but reading the code suggests I have
to commit to a defined arity. So I have some
questions.
1. Is there a better way to read from a
database (i.e., defining my own `InputFormat` using
Slick)?
2. To get the above example working, what
should I supply to `createInput`?
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Thanks. Need to dive in a bit better, but I did clarify some things in my mind which bear mentioning.
1. Sourcing JDBC data is not a streaming operation, but a batching one. Which makes sense, since you generally slurp rather than stream relational data, so within the constraints provided you’ll be operating on whole result sets. 2. Kafka is useful for mating batch processes (like slurping a database) with stream ones (reading out the results of a database query then distributed to various processing nodes).
I suspected as much (the tuple size limitation). Creating my own InputFormat seems to be the best solution, but before i go down that rabbit hole I wanted to see at least a semi-trivial working example of JDBCInputFormat with Scala 2.11.
I’d appreciate a look at that prototype if its publicly available (even if it is Java). I might glean a hint from it.
you can always create your own
InputFormat, but there is no AbstractJDBCInputFormat if that's
what you were looking for.
When you say arbitrary tuple size, do you mean a) a size greater
than 25, or b) tuples of different sizes?
If a) unless you are fine with using nested tuples you won't get
around the tuple size limitation. Since the user has to be aware
of the nesting (since the fields can be accessed directly via
tuple.f0 etc), this can't really be done in a general-purpose
fashion.
If b) this will straight-up not work with tuples.
You could use POJO's though. then you could also group by column
names.
I'm not sure about Scala, but in the Java Stream API you can pass
the InputFormat and the TypeInformation into createInput.
I've recently did a prototype where the input type is determined
automatically by querying the database. If this is a problem for
you feel free to ping me.
On 09.03.2016 03:17, Prez Cannady wrote:
I’m attempting to create a stream using
JDBCInputFormat. Objective is to convert each record into a
tuple and then serialize for input into a Kafka topic. Here’s
what I have so far.
```
val env =
StreamExecutionEnvironment.getExecutionEnvironment
val inputFormat =
JDBCInputFormat.buildJDBCInputFormat()
.setDrivername("org.postgresql.Driver")
.setDBUrl("jdbc:postgresql:test")
.setQuery("select name from persons")
.finish()
val stream : DataStream[Tuple1[String]] =
env.createInput(...)
```
I think this is essentially what I want to do. It
would be nice if I could return tuples of arbitrary length, but
reading the code suggests I have to commit to a defined arity.
So I have some questions.
1. Is there a better way to read from a database
(i.e., defining my own `InputFormat` using Slick)?
2. To get the above example working, what should I
supply to `createInput`?
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Locked
