support default value while import

[xuhuijun]

we are migrating data from neo4j to nebula by using csv file. There is one field which type is bool. In neo4j export csv file, the value could be true/false/empty. In such case, importing failed due to nebula reject empty value.

So we need to add default value while filed value is missing. Below is the example we want:

data.csv: 100,true, 101,,

Schema definition: schema: type: vertex vertex: tags:

• name: collection props:
  • name: used type: bool default: false

The second line in data will use default value false and below will load to nebula: 100(true) 101(false)

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

:white_check_mark: HarrisChu
:white_check_mark: Aiee
:x: xuhuijun
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[yixinglu]

Thanks @xuhuijun

Could you add some test data in the examples folder to test the feature ?

In addition, don't forget to sign the CLA by click the badge in above comment.

[veezhang]

@xuhuijun Thanks!I create an PR #243 to support default value, and thanks again and again.