> Currently, for CTAS or CREATE MATERIALIZED VIEW(CMV) without if-not-exists > clause, the existence of the relation gets checked during the execution > of the select part and an error is thrown there. > All the unnecessary rewrite and planning for the select part would have > happened just to fail later. However, if if-not-exists clause is present, > then a notice is issued and returned immediately without any further rewrite > or planning for . This seems somewhat inconsistent to me. > > I propose to check the relation existence early in ExecCreateTableAs() as > well as in ExplainOneUtility() and throw an error in case it exists already > to avoid unnecessary rewrite, planning and execution of the select part. > > Attaching a patch. Note that I have not added any test cases as the existing > test cases in create_table.sql and matview.sql would cover the code. > > Thoughts?
Personally, I think it make sense, as other CMD(such as create extension/index ...) throw that error before any further operation too. I am just a little worried about the behavior change of [explain CTAS]. May be someone will complain the change from normal explaininfo to error output. And I took a look into the patch. + StringInfoData emsg; + + initStringInfo(&emsg); + + if (level == NOTICE) + appendStringInfo(&emsg, Using variable emsg and level seems a little complicated to me. How about just: if (!is_explain && ctas->if_not_exists) ereport(NOTICE,xxx else ereport(ERROR,xxx Best regards, houzj
