okumin commented on code in PR #5077:
URL: https://github.com/apache/hive/pull/5077#discussion_r1485585374
##########
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/reloperators/HiveTableScan.java:
##########
@@ -202,6 +203,12 @@ public HiveTableScan copyIncludingTable(RelDataType
newRowtype) {
// Also include partition list key to trigger cost evaluation even if an
// expression was already generated.
@Override public RelWriter explainTerms(RelWriter pw) {
+ if (pw instanceof RelTreeSignatureWriter) {
+ return super.explainTerms(pw)
+ .item("tableScanTrait", this.tableScanTrait)
+ .itemIf("fromVersion", ((RelOptHiveTable)
table).getHiveTableMD().getVersionIntervalFrom(),
+ isNotBlank(((RelOptHiveTable)
table).getHiveTableMD().getVersionIntervalFrom()));
Review Comment:
I added some attributes that could differentiate two HiveTableScans. We may
not need these ones here.
There is one potential problem in my mind. HiveTableScan doesn't retain the
equivalents of `TableScanDesc#getPredicateString` or
`TableScanDesc#getRowLimit`. So, we can't unify ASTNodes or RelNodes of
HiveTableScan based on signatures. Otherwise, Operators will be over-unified
later.
Currently, we link only HiveFilter RelNodes using RelTreeSignatures(we link
HiveTableScan with its ASTNode, but don't link it with the signature). So, the
existence of `TableScanDesc#getPredicateString` doesn't matter to us.
Also, [CBO is disabled when TABLESAMPLE is
used](https://github.com/apache/hive/blob/rel/release-4.0.0-beta-1/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/HiveCalciteUtil.java#L105).
So, we can say `TableScanDesc#getRowLimit` doesn't cause an issue in the world
of RelNodes. I expect we could push down the row count to HiveTableScan when we
support TABLESAMPLE in CBO.
So, in my current understanding, this PR doesn't cause an immediate problem.
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