Add SQL support for referencing fields in structs

[alamb]

Note: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-10761

I would like to be able to use SQL to query data sources such as Parquet and JSON that support nested types.

Example:
{code:java}
SELECT id, first_name, address.zip AS zip_code FROM customer{code}

[houqp]

In @Igosuki 's recent PR (#1006) for adding list indexing support, he proposed using field["key"] to access nested struct field, which I think makes the query more readable. For example, foo.id could mean accessing the id attribute from an unqualified foo column or accessing the id column from the table foo. foo["id"] makes it clear that id is for accessing of struct field.

[houqp]

I think we are almost there with this feature, see my comment in #1006 (comment).

[Igosuki]

Sorry I haven't had time to finish the PR as I'm traveling. But indeed the patch provides unified access for nested bracket notations. Using a '.' is more a JSON path expression (see hive and postures dialects for instance) Le lun. 18 oct. 2021 à 05:07, QP Hou ***@***.***> a écrit :

…

I think we are almost there with this feature, see my comment in #1006 (comment) <#1006 (comment)> . — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#119 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADDFBVLJB4PHXDJF7KFIMTUHOFQFANCNFSM43S4FFWA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[Igosuki]

#1204