Github user zellerh commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/1306#discussion_r152346606
--- Diff: core/sql/optimizer/IndexDesc.cpp ---
@@ -802,10 +802,30 @@ IndexProperty::compareIndexPromise(const
IndexProperty *ixProp) const
const IndexDesc * index = getIndexDesc();
const IndexDesc * otherIndex = ixProp->getIndexDesc();
- if ( ((IndexColumn
*)(index->getIndexKey()[0]).getItemExpr())->getDefinition() !=
- ((IndexColumn
*)(otherIndex->getIndexKey()[0]).getItemExpr())->getDefinition() )
-
- return INCOMPATIBLE;
+
+ // If the two indexes have differing leading columns, consider them
incompatible.
+ // For this check, we ignore the "_SALT_" column if both are salted.
+ CollIndex columnToCheck = 0;
+ NABoolean done = FALSE;
+ while (!done)
+ {
+ if (columnToCheck >= index->getIndexKey().entries())
+ return INCOMPATIBLE; // must be one of the indexes is just
"_SALT_" (seems unlikely actually)
+ else if (columnToCheck >= otherIndex->getIndexKey().entries())
+ return INCOMPATIBLE; // must be one of the indexes is just
"_SALT_" (seems unlikely actually)
+ else
+ {
+ IndexColumn * indexCol = (IndexColumn
*)(index->getIndexKey()[columnToCheck]).getItemExpr();
+ IndexColumn * otherIndexCol = (IndexColumn
*)(otherIndex->getIndexKey()[columnToCheck]).getItemExpr();
+ if ( indexCol->getNAColumn()->isSaltColumn() &&
+ otherIndexCol->getNAColumn()->isSaltColumn() )
--- End diff --
Just wanted to bring this up, I can also live with both solutions. The
computation of predicates for salt and division columns is similar, both are
computed from user columns. The main difference is that the expressions of
divisioning columns are monotonically increasing. I would have thought that the
following indexes should be treated as incompatible:
create index ix1 on t(a) division like table;
create index ix2 on t(b) division like table;
---
