Github user skambha commented on a diff in the pull request:
https://github.com/apache/spark/pull/14897#discussion_r77879554
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
---
@@ -451,7 +464,7 @@ class SessionCatalog(
if (isTemporaryTable(name)) {
true
} else {
- externalCatalog.tableExists(db, table)
+ globalTempViews.get(table).isDefined ||
externalCatalog.tableExists(db, table)
--- End diff --
I think the tableExists should also follow the similar semantics as the
lookupRelation.
i.e. If database in TableIdentifier is defined, then table existence should
be checked against the defined database and table.
The code comment is correct but the code is not enforcing it in
tableExists.
The table/view resolution in the lookupRelation is
- if database is defined, then fetch the table/view from it.
- if database is not defined, then the following checks happen in the
particular order.
a) check if it a local temp view exists
b) if a global temp view with name exists.
c) If not, then check if there is a table/view in current db.
Currently, if I do tableExists(db1.t1), it will return true if a global
temp view t1 exists but there is no db1.t1 in the externalCatalog.
In tableExists method, we should enforce the check if database is defined,
we should check against the externalCatalog and not the globalTempView... and
enhance it to follow the resolution semantics in the lookupRelation.
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