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[GitHub] [hive] soumyakanti3578 opened a new pull request #2360: [HIVE-25209 | https://issues.apache.org/jira/browse/HIVE-25209]SELECT query with SUM function producing unexpected result
soumyakanti3578 opened a new pull request #2360:
URL: https://github.com/apache/hive/pull/2360
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r666359063
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java
##########
@@ -397,6 +397,11 @@ else if (getGbyKeyType(cgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
if (udaf instanceof GenericUDAFSum) {
// long/double/decimal
ExprNodeDesc desc = aggr.getParameters().get(0);
+ // add null for SUM(1), when the table is empty. Without this, category = LONG, and the result is 0
+ // instead of NULL.
+ if (desc instanceof ExprNodeConstantDesc && rowCnt == 0) {
+ oneRow.add(null);
+ }
Review comment:
down below it will add a second value to the row (`oneRow`) ; try a test with multiple sum-s like 2
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[GitHub] [hive] soumyakanti3578 commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
soumyakanti3578 commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r656373540
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java
##########
@@ -397,6 +397,11 @@ else if (getGbyKeyType(cgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
if (udaf instanceof GenericUDAFSum) {
// long/double/decimal
ExprNodeDesc desc = aggr.getParameters().get(0);
+ // return null for SUM(1), when the table is empty. Without this, category = LONG, and the result is 0
+ // instead of NULL.
+ if (desc instanceof ExprNodeConstantDesc && rowCnt == 0) {
+ return null;
Review comment:
Do you mean, instead of returning null, I should return oneRow.add(null) ?
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r656268281
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java
##########
@@ -397,6 +397,11 @@ else if (getGbyKeyType(cgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
if (udaf instanceof GenericUDAFSum) {
// long/double/decimal
ExprNodeDesc desc = aggr.getParameters().get(0);
+ // return null for SUM(1), when the table is empty. Without this, category = LONG, and the result is 0
+ // instead of NULL.
+ if (desc instanceof ExprNodeConstantDesc && rowCnt == 0) {
+ return null;
Review comment:
if you could add a `null` to the result - then the whole computation would be removed
there is a chance that `oneRow.add(null)` will work
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r656384319
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java
##########
@@ -397,6 +397,11 @@ else if (getGbyKeyType(cgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
if (udaf instanceof GenericUDAFSum) {
// long/double/decimal
ExprNodeDesc desc = aggr.getParameters().get(0);
+ // return null for SUM(1), when the table is empty. Without this, category = LONG, and the result is 0
+ // instead of NULL.
+ if (desc instanceof ExprNodeConstantDesc && rowCnt == 0) {
+ return null;
Review comment:
yes; I think that will work - but make sure to not execute further this conditional :)
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[GitHub] [hive] kgyrtkirk merged pull request #2360: HIVE-25209: SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk merged pull request #2360:
URL: https://github.com/apache/hive/pull/2360
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r655492864
##########
File path: ql/src/test/queries/clientpositive/select_sum.q
##########
@@ -0,0 +1,14 @@
+DROP DATABASE IF EXISTS db5 CASCADE;
+CREATE DATABASE db5;
+use db5;
+CREATE TABLE IF NOT EXISTS t1(c0 boolean, c1 boolean);
+
+SELECT SUM(1) FROM t1;
Review comment:
could you please add an explain to see the optimization in action?
##########
File path: ql/src/test/queries/clientpositive/select_sum.q
##########
@@ -0,0 +1,14 @@
+DROP DATABASE IF EXISTS db5 CASCADE;
+CREATE DATABASE db5;
+use db5;
Review comment:
these lines could be removed
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[GitHub] [hive] kgyrtkirk merged pull request #2360: HIVE-25209: SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk merged pull request #2360:
URL: https://github.com/apache/hive/pull/2360
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r664637117
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java
##########
@@ -397,6 +397,11 @@ else if (getGbyKeyType(cgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
if (udaf instanceof GenericUDAFSum) {
// long/double/decimal
ExprNodeDesc desc = aggr.getParameters().get(0);
+ // return null for SUM(1), when the table is empty. Without this, category = LONG, and the result is 0
+ // instead of NULL.
+ if (desc instanceof ExprNodeConstantDesc && rowCnt == 0) {
+ return oneRow.add(null);
Review comment:
this `return` doesn't look right to me - it may work correctly if you around only selecting the aggregate - but what happens if you have more?
I believe you should execute `oneRow.add(null)` ; bail out the rest of this conditional - and let the code continue with the remaining aggregates if there is any
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[GitHub] [hive] kgyrtkirk commented on a change in pull request #2360: [HIVE-25209]SELECT query with SUM function producing unexpected result
Posted by GitBox <gi...@apache.org>.
kgyrtkirk commented on a change in pull request #2360:
URL: https://github.com/apache/hive/pull/2360#discussion_r655492864
##########
File path: ql/src/test/queries/clientpositive/select_sum.q
##########
@@ -0,0 +1,14 @@
+DROP DATABASE IF EXISTS db5 CASCADE;
+CREATE DATABASE db5;
+use db5;
+CREATE TABLE IF NOT EXISTS t1(c0 boolean, c1 boolean);
+
+SELECT SUM(1) FROM t1;
Review comment:
could you please add an explain to see the optimization in action?
##########
File path: ql/src/test/queries/clientpositive/select_sum.q
##########
@@ -0,0 +1,14 @@
+DROP DATABASE IF EXISTS db5 CASCADE;
+CREATE DATABASE db5;
+use db5;
Review comment:
these lines could be removed
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