[ https://issues.apache.org/jira/browse/FLINK-5185?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15710644#comment-15710644 ]
Kurt Young edited comment on FLINK-5185 at 12/1/16 2:45 AM: ------------------------------------------------------------ Hi [~fhueske], thanks for the reply. Actually, this issue reflects a fundamental question we need to answer: "who decides the RowType when you scan the table?" or "who is the schema authority?". Apparently, your suggestion leads us with the answer: {{BatchTableSouceScan}}. But i think the answer should be {{TableSource}}, which is responsible for all the real work. Let {{BatchTableSouceScan}} holds the optional parameters for projection or filter will do the work for now, but when we begin to introduce complex {{TableSources}}, which can even let you push part of the query down, the {{BatchTableSouceScan}} will no longer competent for this job. So i propose to let {{TableSource}} be the RowType authority, and we can and only can get RowType information from {{TableSource}}. And also, only {{TableSource}} can decide how to react to the provided projection columns or filter condition or even the original query. {{BatchTableSouceScan}} should pass these information to the {{TableSource}}, and just wait for the new RowType comes from the new {{TableSource}}. After all, RowType is the only thing {{BatchTableSouceScan}} cares and should care. was (Author: ykt836): Hi [~fhueske], thanks for the reply. Actually, this issue reflects a fundamental question we need to answer: "who decides the RowType when you scan the table?" or "who is the schema authority?". Apparently, your suggestion leads us with the answer: {{BatchTableSouceScan}}. But i think the answer should be {{TableSource}}, which is responsible for all the real work. Let {{BatchTableSouceScan}} holds the optional parameters for projection or filter will do the work for now, but when we begin to introduce complex {{TableSources}}, which can even let you push part of the query down, the {{BatchTableSouceScan}} will no longer competent for his job. So i propose to let {{TableSource}} be the RowType authority, and we can and only can get RowType information from {{TableSource}}. And also, only {{TableSource}} can decide how to react to the provided projection columns or filter condition or even the original query. {{BatchTableSouceScan}} should pass these information to the {{TableSource}}, and just wait for the new RowType comes from the new {{TableSource}}. After all, RowType is the only thing {{BatchTableSouceScan}} cares and should care. > Decouple BatchTableSourceScan with TableSourceTable > --------------------------------------------------- > > Key: FLINK-5185 > URL: https://issues.apache.org/jira/browse/FLINK-5185 > Project: Flink > Issue Type: Improvement > Components: Table API & SQL > Affects Versions: 1.2.0 > Reporter: Kurt Young > Assignee: zhangjing > Priority: Minor > > As the components' relationship show in this design doc: > https://docs.google.com/document/d/1PBnEbOcFHlEF1qGGAUgJvINdEXzzFTIRElgvs4-Tdeo/ > We found it's been annoying for {{BatchTableSourceScan}} directly holding > {{TableSourceTable}}, and refer to {{TableSource}} further. It's ok if the > relationship is immutable, but when we want to change the {{TableSource}} > when applying optimizations, it will cause some conflicts and > misunderstanding. > Since there is only one way to change {{TableSource}}, which is creating a > new {{TableSourceTable}} to hold the new {{TableSource}}, and create a new > {{BatchTableSourceScan}} pointing to the {{TableSourceTable}} which just > created. The annoying part is the {{RelOptTable}} comes from the super class > {{TableScan}} still holds the connection to the original {{TableSourceTable}} > and {{TableSource}}. It will cause some misunderstanding, which one should > the {{Scan}} rely to, and what's difference between these tables. > Besides, {{TableSourceTable}} is not very useful in {{BatchTableSourceScan}}, > the only thing {{Scan}} cares is the {{RowType}} it returns, since this is > and should be decided by {{TableSource}}. So we can let > {{BatchTableSourceScan}} directly holding {{TableSource}} instead of holding > {{TableSourceTable}}.If some original information are needed, find table > through {{RelOptTable}}. -- This message was sent by Atlassian JIRA (v6.3.4#6332)