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https://issues.apache.org/jira/browse/SQOOP-1168?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Veena Basavaraj updated SQOOP-1168:
-----------------------------------
Description:
The formal design wiki is here
https://cwiki.apache.org/confluence/display/SQOOP/Incremental+From+To+Design
was:
The formal design wiki is here
https://cwiki.apache.org/confluence/display/SQOOP/Incremental+From+To+Design
Following is some notes while investigating the design
Initial plan is to follow roughly the same design as Sqoop 1, except provide
pluggability to start this through a REST API.
Relevant code in Sqoop 1 ( to ensure parity with tests and features ). Also
note that Sqoop 1 was less generic than Sqoop2 in terms of the from and to.
The From was a SQL and TO was HDFS/ Hive...so this is no longer true in SQOOP2.
It cab be from HDFS to SQL or from MongoDB to MySQL.
https://github.com/apache/sqoop/blob/trunk/src/java/org/apache/sqoop/tool/ImportTool.java
https://github.com/apache/sqoop/blob/trunk/src/java/org/apache/sqoop/mapreduce/MergeJob.java
https://github.com/apache/sqoop/blob/trunk/src/java/org/apache/sqoop/util/AppendUtils.java
https://github.com/apache/sqoop/blob/trunk/src/test/com/cloudera/sqoop/TestAppendUtils.java
https://github.com/apache/sqoop/blob/trunk/src/test/org/apache/sqoop/manager/oracle/OracleIncrementalImportTest.java
https://github.com/apache/sqoop/blob/trunk/src/test/com/cloudera/sqoop/TestIncrementalImport.java
Some things I considered.
1. Do we need the 2 modes,simpler sequential / append case based on a simple
predicate ( that can be the default) and more generic random set of records (
based on a complex predicate ). The only reason these 2 modes might make sense,
is the simple append use case can be for majority of the part be handled by
the sqoop. There is very little logic to add per connector.
The more complex case where we can have random selection of records to read and
even write them out in many different ways requires a custom logic. We can
certainly provide some common implementation of doing such updates, such as
writing a new dataset for the delta records and the merging duplicate row data
sets based on the last updated value.
2. What are the phases of the Incremental read/ write process for each
connector look like?. Should this be independent stage in the job lifecycle
complementing the Extractor or another api on the Extractor to do deltaExtract
or just another config object on the FromJobConfiguration where the computed
predicate string ( combination of raw predicate and the last value from the
FromConfig of the job)?
Seems like just a field on the FromJobConfiguration suffices. It can be used
both in the Partitioner and Extractor.
The FromJobConfiguration can have a dynamically created config object in its
list that is reserved for all the incremental related fields. One of the field
in it will be the following predicate.
Say one way of supporting predicate is via a proper schema like this.
{code}
{
type : "append"
columns : "id"
operator : ">="
value : "34"
}
{code}
The FromJobConfiguration might have the actual query string WHERE id > = '34'
in the string format. Alternatively. If we do not go with the predicates and
use loose fields like in Sqoop1, then the FromJobConfiguration will hold these
fields and its values. The FromConfig will hold the last processed value, so
that it can be used in the subsequent runs to indicate from where to start.
3. Similarly in terms of Writing /Loading, the ToJobConfiguration will have
information in it to indicate if this was a delta write. Based on the predicate
type/ modes ( SEQUENTIAL( APPEND) / RANDOM) , the loader can decide how to
write the data.
4. Does storing the last-processed-value in the job submission make it easier?
in that case we would need 2 fields, the last_read_value for the FROM side and
the last_written_value for the TO. I would consider submission, since these
values are a result of job run...but still store predicate in the job config (
with the given last value )
5. Even the last step, very inaptly names Destroyer, after successful might
need this info to finally record the values in the submission / configs and
other related stats of the incremental read/ writes ..So the FROM and the TO
destroyer will need to do this part.
> Sqoop2: Incremental and Delta updates ( formerly called Incremental Import )
> ----------------------------------------------------------------------------
>
> Key: SQOOP-1168
> URL: https://issues.apache.org/jira/browse/SQOOP-1168
> Project: Sqoop
> Issue Type: Bug
> Reporter: Hari Shreedharan
> Assignee: Veena Basavaraj
> Fix For: 1.99.5
>
>
> The formal design wiki is here
> https://cwiki.apache.org/confluence/display/SQOOP/Incremental+From+To+Design
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