I think it makes sense for the case when timestamp is provided in the payload (including pubsub message attributes). We can mark the field as an event timestamp. But if the timestamp is internally defined by the source (pubsub message publish time) and not exposed in the event body, then we need a source-specific mechanism to extract and map the event timestamp to the schema. This is, of course, if we don't automatically add a magic timestamp field which Beam SQL can populate behind the scenes and add to the schema. I want to avoid this magic path for now.
On Thu, May 3, 2018 at 11:10 AM Andrew Pilloud <apill...@google.com> wrote: > This sounds awesome! > > Is event timestamp something that we need to specify for every source? If > so, I would suggest we add this as a first class option on CREATE TABLE > rather then something hidden in TBLPROPERTIES. > > Andrew > > On Wed, May 2, 2018 at 10:30 AM Anton Kedin <ke...@google.com> wrote: > >> Hi >> >> I am working on adding functionality to support querying Pubsub messages >> directly from Beam SQL. >> >> *Goal* >> Provide Beam users a pure SQL solution to create the pipelines with >> Pubsub as a data source, without the need to set up the pipelines in >> Java before applying the query. >> >> *High level approach* >> >> - >> - Build on top of PubsubIO; >> - Pubsub source will be declared using CREATE TABLE DDL statement: >> - Beam SQL already supports declaring sources like Kafka and Text >> using CREATE TABLE DDL; >> - it supports additional configuration using TBLPROPERTIES clause. >> Currently it takes a text blob, where we can put a JSON configuration; >> - wrapping PubsubIO into a similar source looks feasible; >> - The plan is to initially support messages only with JSON payload: >> - >> - more payload formats can be added later; >> - Messages will be fully described in the CREATE TABLE statements: >> - event timestamps. Source of the timestamp is configurable. It is >> required by Beam SQL to have an explicit timestamp column for windowing >> support; >> - messages attributes map; >> - JSON payload schema; >> - Event timestamps will be taken either from publish time or >> user-specified message attribute (configurable); >> >> Thoughts, ideas, comments? >> >> More details are in the doc here: >> https://docs.google.com/document/d/1wIXTxh-nQ3u694XbF0iEZX_7-b3yi4ad0ML2pcAxYfE >> >> >> Thank you, >> Anton >> >
