Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/3510#discussion_r21068472
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
---
@@ -219,6 +219,27 @@ trait HiveTypeCoercion {
if (b.right.dataType == widestType) b.right else
Cast(b.right, widestType)
b.makeCopy(Array(newLeft, newRight))
}.getOrElse(b) // If there is no applicable conversion, leave
expression unchanged.
+
+ case c @ Coalesce(exps) =>
+ val valueTypes = exps.map (_.dataType)
+ if (valueTypes.distinct.size > 1) {
+ val commonType = valueTypes.reduce { (v1, v2) =>
+ // When a string is found on one side, make the other side a
string too.
+ if (v1 == StringType || v2 == StringType) {
+ StringType
--- End diff --
I've tried `select coalesce(cast(key as date), key) from src;` in Hive,
seems it does not work in this way (convert the `DateType` into `StringType`),
it outputs:
```
hive> select coalesce(cast(key as date), key) from src;
FAILED: SemanticException [Error 10016]: Line 1:36 Argument type mismatch
'key': The expressions after COALESCE should all have the same type: "date" is
expected but "string" is found
14/11/30 19:36:22 ERROR ql.Driver: FAILED: SemanticException [Error 10016]:
Line 1:36 Argument type mismatch 'key': The expressions after COALESCE should
all have the same type: "date" is expected but "string" is found
org.apache.hadoop.hive.ql.parse.SemanticException: Line 1:36 Argument type
mismatch 'key': The expressions after COALESCE should all have the same type:
"date" is expected but "string" is found
at
org.apache.hadoop.hive.ql.parse.TypeCheckProcFactory$DefaultExprProcessor.process(TypeCheckProcFactory.java:1102)
at
org.apache.hadoop.hive.ql.lib.DefaultRuleDispatcher.dispatch(DefaultRuleDispatcher.java:90)
at
org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.dispatchAndReturn(DefaultGraphWalker.java:94)
at
org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.dispatch(DefaultGraphWalker.java:78)
at
org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.walk(DefaultGraphWalker.java:132)
at
org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.startWalking(DefaultGraphWalker.java:109)
at
org.apache.hadoop.hive.ql.parse.TypeCheckProcFactory.genExprNode(TypeCheckProcFactory.java:177)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genAllExprNodeDesc(SemanticAnalyzer.java:8628)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genExprNodeDesc(SemanticAnalyzer.java:8584)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genSelectPlan(SemanticAnalyzer.java:2639)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genSelectPlan(SemanticAnalyzer.java:2436)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genPostGroupByBodyPlan(SemanticAnalyzer.java:7364)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genBodyPlan(SemanticAnalyzer.java:7320)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genPlan(SemanticAnalyzer.java:8123)
at
org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.analyzeInternal(SemanticAnalyzer.java:8349)
at
org.apache.hadoop.hive.ql.parse.BaseSemanticAnalyzer.analyze(BaseSemanticAnalyzer.java:284)
at org.apache.hadoop.hive.ql.Driver.compile(Driver.java:441)
at org.apache.hadoop.hive.ql.Driver.compile(Driver.java:342)
at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:977)
at org.apache.hadoop.hive.ql.Driver.run(Driver.java:888)
at
org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:259)
at
org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:216)
at
org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:413)
at
org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:781)
at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:675)
at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:614)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.main(RunJar.java:156)
```
Seems type converting only applicable among `NumbericType`s and
`StringType`. Sorry, I couldn't provide more information, probably a Hive
QuerySuite should be better to verify that.
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