## What changes were proposed in this pull request?
This removes the serialization test from RegexpExpressionsSuite and
replaces it by serializing all expressions in checkEvaluation.
This also fixes math constant expressions by making LeafMathExpression
Serializable and fixes NumberFormat values that are null or invalid
after serialization.
## How was this patch tested?
This patch is to tests.
Author: Ryan Blue <blue@apache.org>
Closes#15847 from rdblue/SPARK-18387-fix-serializable-expressions.
## What changes were proposed in this pull request?
As of current 2.1, INSERT OVERWRITE with dynamic partitions against a Datasource table will overwrite the entire table instead of only the partitions matching the static keys, as in Hive. It also doesn't respect custom partition locations.
This PR adds support for all these operations to Datasource tables managed by the Hive metastore. It is implemented as follows
- During planning time, the full set of partitions affected by an INSERT or OVERWRITE command is read from the Hive metastore.
- The planner identifies any partitions with custom locations and includes this in the write task metadata.
- FileFormatWriter tasks refer to this custom locations map when determining where to write for dynamic partition output.
- When the write job finishes, the set of written partitions is compared against the initial set of matched partitions, and the Hive metastore is updated to reflect the newly added / removed partitions.
It was necessary to introduce a method for staging files with absolute output paths to `FileCommitProtocol`. These files are not handled by the Hadoop output committer but are moved to their final locations when the job commits.
The overwrite behavior of legacy Datasource tables is also changed: no longer will the entire table be overwritten if a partial partition spec is present.
cc cloud-fan yhuai
## How was this patch tested?
Unit tests, existing tests.
Author: Eric Liang <ekl@databricks.com>
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15814 from ericl/sc-5027.
## What changes were proposed in this pull request?
This PR corrects several partition related behaviors of `ExternalCatalog`:
1. default partition location should not always lower case the partition column names in path string(fix `HiveExternalCatalog`)
2. rename partition should not always lower case the partition column names in updated partition path string(fix `HiveExternalCatalog`)
3. rename partition should update the partition location only for managed table(fix `InMemoryCatalog`)
4. create partition with existing directory should be fine(fix `InMemoryCatalog`)
5. create partition with non-existing directory should create that directory(fix `InMemoryCatalog`)
6. drop partition from external table should not delete the directory(fix `InMemoryCatalog`)
## How was this patch tested?
new tests in `ExternalCatalogSuite`
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15797 from cloud-fan/partition.
## What changes were proposed in this pull request?
This makes the result value both transient and lazy, so that if the RegExpReplace object is initialized then serialized, `result: StringBuffer` will be correctly initialized.
## How was this patch tested?
* Verified that this patch fixed the query that found the bug.
* Added a test case that fails without the fix.
Author: Ryan Blue <blue@apache.org>
Closes#15834 from rdblue/SPARK-18368-fix-regexp-replace.
## What changes were proposed in this pull request?
This makes the result value both transient and lazy, so that if the RegExpReplace object is initialized then serialized, `result: StringBuffer` will be correctly initialized.
## How was this patch tested?
* Verified that this patch fixed the query that found the bug.
* Added a test case that fails without the fix.
Author: Ryan Blue <blue@apache.org>
Closes#15816 from rdblue/SPARK-18368-fix-regexp-replace.
## What changes were proposed in this pull request?
We generate bitmasks for grouping sets during the parsing process, and use these during analysis. These bitmasks are difficult to work with in practice and have lead to numerous bugs. This PR removes these and use actual sets instead, however we still need to generate these offsets for the grouping_id.
This PR does the following works:
1. Replace bitmasks by actual grouping sets durning Parsing/Analysis stage of CUBE/ROLLUP/GROUPING SETS;
2. Add new testsuite `ResolveGroupingAnalyticsSuite` to test the `Analyzer.ResolveGroupingAnalytics` rule directly;
3. Fix a minor bug in `ResolveGroupingAnalytics`.
## How was this patch tested?
By existing test cases, and add new testsuite `ResolveGroupingAnalyticsSuite` to test directly.
Author: jiangxingbo <jiangxb1987@gmail.com>
Closes#15484 from jiangxb1987/group-set.
## What changes were proposed in this pull request?
In RewriteDistinctAggregates rewrite funtion,after the UDAF's childs are mapped to AttributeRefference, If the UDAF(such as ApproximatePercentile) has a foldable TypeCheck for the input, It will failed because the AttributeRefference is not foldable,then the UDAF is not resolved, and then nullify on the unresolved object will throw a Exception.
In this PR, only map Unfoldable child to AttributeRefference, this can avoid the UDAF's foldable TypeCheck. and then only Expand Unfoldable child, there is no need to Expand a static value(foldable value).
**Before sql result**
> select percentile_approxy(key,0.99999),count(distinct key),sume(distinc key) from src limit 1
> org.apache.spark.sql.catalyst.analysis.UnresolvedException: Invalid call to dataType on unresolved object, tree: 'percentile_approx(CAST(src.`key` AS DOUBLE), CAST(0.99999BD AS DOUBLE), 10000)
> at org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute.dataType(unresolved.scala:92)
> at org.apache.spark.sql.catalyst.optimizer.RewriteDistinctAggregates$.org$apache$spark$sql$catalyst$optimizer$RewriteDistinctAggregates$$nullify(RewriteDistinctAggregates.scala:261)
**After sql result**
> select percentile_approxy(key,0.99999),count(distinct key),sume(distinc key) from src limit 1
> [498.0,309,79136]
## How was this patch tested?
Add a test case in HiveUDFSuit.
Author: root <root@iZbp1gsnrlfzjxh82cz80vZ.(none)>
Closes#15668 from windpiger/RewriteDistinctUDAFUnresolveExcep.
### What changes were proposed in this pull request?
Based on the discussion in [SPARK-18209](https://issues.apache.org/jira/browse/SPARK-18209). It doesn't really make sense to create permanent views based on temporary views or temporary UDFs.
To disallow the supports and issue the exceptions, this PR needs to detect whether a temporary view/UDF is being used when defining a permanent view. Basically, this PR can be split to two sub-tasks:
**Task 1:** detecting a temporary view from the query plan of view definition.
When finding an unresolved temporary view, Analyzer replaces it by a `SubqueryAlias` with the corresponding logical plan, which is stored in an in-memory HashMap. After replacement, it is impossible to detect whether the `SubqueryAlias` is added/generated from a temporary view. Thus, to detect the usage of a temporary view in view definition, this PR traverses the unresolved logical plan and uses the name of an `UnresolvedRelation` to detect whether it is a (global) temporary view.
**Task 2:** detecting a temporary UDF from the query plan of view definition.
Detecting usage of a temporary UDF in view definition is not straightfoward.
First, in the analyzed plan, we are having different forms to represent the functions. More importantly, some classes (e.g., `HiveGenericUDF`) are not accessible from `CreateViewCommand`, which is part of `sql/core`. Thus, we used the unanalyzed plan `child` of `CreateViewCommand` to detect the usage of a temporary UDF. Because the plan has already been successfully analyzed, we can assume the functions have been defined/registered.
Second, in Spark, the functions have four forms: Spark built-in functions, built-in hash functions, permanent UDFs and temporary UDFs. We do not have any direct way to determine whether a function is temporary or not. Thus, we introduced a function `isTemporaryFunction` in `SessionCatalog`. This function contains the detailed logics to determine whether a function is temporary or not.
### How was this patch tested?
Added test cases.
Author: gatorsmile <gatorsmile@gmail.com>
Closes#15764 from gatorsmile/blockTempFromPermViewCreation.
## What changes were proposed in this pull request?
This PR proposes to match up the behaviour of `to_json` to `from_json` function for null-safety.
Currently, it throws `NullPointException` but this PR fixes this to produce `null` instead.
with the data below:
```scala
import spark.implicits._
val df = Seq(Some(Tuple1(Tuple1(1))), None).toDF("a")
df.show()
```
```
+----+
| a|
+----+
| [1]|
|null|
+----+
```
the codes below
```scala
import org.apache.spark.sql.functions._
df.select(to_json($"a")).show()
```
produces..
**Before**
throws `NullPointException` as below:
```
java.lang.NullPointerException
at org.apache.spark.sql.catalyst.json.JacksonGenerator.org$apache$spark$sql$catalyst$json$JacksonGenerator$$writeFields(JacksonGenerator.scala:138)
at org.apache.spark.sql.catalyst.json.JacksonGenerator$$anonfun$write$1.apply$mcV$sp(JacksonGenerator.scala:194)
at org.apache.spark.sql.catalyst.json.JacksonGenerator.org$apache$spark$sql$catalyst$json$JacksonGenerator$$writeObject(JacksonGenerator.scala:131)
at org.apache.spark.sql.catalyst.json.JacksonGenerator.write(JacksonGenerator.scala:193)
at org.apache.spark.sql.catalyst.expressions.StructToJson.eval(jsonExpressions.scala:544)
at org.apache.spark.sql.catalyst.expressions.Alias.eval(namedExpressions.scala:142)
at org.apache.spark.sql.catalyst.expressions.InterpretedProjection.apply(Projection.scala:48)
at org.apache.spark.sql.catalyst.expressions.InterpretedProjection.apply(Projection.scala:30)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
```
**After**
```
+---------------+
|structtojson(a)|
+---------------+
| {"_1":1}|
| null|
+---------------+
```
## How was this patch tested?
Unit test in `JsonExpressionsSuite.scala` and `JsonFunctionsSuite.scala`.
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#15792 from HyukjinKwon/SPARK-18295.
## What changes were proposed in this pull request?
Add a function to check if two integers are compatible when invoking `acceptsType()` in `DataType`.
## How was this patch tested?
Manually.
E.g.
```
spark.sql("create table t3(a map<bigint, array<string>>)")
spark.sql("select * from t3 where a[1] is not null")
```
Before:
```
cannot resolve 't.`a`[1]' due to data type mismatch: argument 2 requires bigint type, however, '1' is of int type.; line 1 pos 22
org.apache.spark.sql.AnalysisException: cannot resolve 't.`a`[1]' due to data type mismatch: argument 2 requires bigint type, however, '1' is of int type.; line 1 pos 22
at org.apache.spark.sql.catalyst.analysis.package$AnalysisErrorAt.failAnalysis(package.scala:42)
at org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1$$anonfun$apply$2.applyOrElse(CheckAnalysis.scala:82)
at org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1$$anonfun$apply$2.applyOrElse(CheckAnalysis.scala:74)
at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$transformUp$1.apply(TreeNode.scala:307)
```
After:
Run the sql queries above. No errors.
Author: Weiqing Yang <yangweiqing001@gmail.com>
Closes#15448 from weiqingy/SPARK_17108.
## What changes were proposed in this pull request?
As reported in the jira, sometimes the generated java code in codegen will cause compilation error.
Code snippet to test it:
case class Route(src: String, dest: String, cost: Int)
case class GroupedRoutes(src: String, dest: String, routes: Seq[Route])
val ds = sc.parallelize(Array(
Route("a", "b", 1),
Route("a", "b", 2),
Route("a", "c", 2),
Route("a", "d", 10),
Route("b", "a", 1),
Route("b", "a", 5),
Route("b", "c", 6))
).toDF.as[Route]
val grped = ds.map(r => GroupedRoutes(r.src, r.dest, Seq(r)))
.groupByKey(r => (r.src, r.dest))
.reduceGroups { (g1: GroupedRoutes, g2: GroupedRoutes) =>
GroupedRoutes(g1.src, g1.dest, g1.routes ++ g2.routes)
}.map(_._2)
The problem here is, in `ReferenceToExpressions` we evaluate the children vars to local variables. Then the result expression is evaluated to use those children variables. In the above case, the result expression code is too long and will be split by `CodegenContext.splitExpression`. So those local variables cannot be accessed and cause compilation error.
## How was this patch tested?
Jenkins tests.
Please review https://cwiki.apache.org/confluence/display/SPARK/Contributing+to+Spark before opening a pull request.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#15693 from viirya/fix-codege-compilation-error.
## What changes were proposed in this pull request?
We have an undocumented naming convention to call expression unit tests ExpressionsSuite, and the end-to-end tests FunctionsSuite. It'd be great to make all test suites consistent with this naming convention.
## How was this patch tested?
This is a test-only naming change.
Author: Reynold Xin <rxin@databricks.com>
Closes#15793 from rxin/SPARK-18296.
## What changes were proposed in this pull request?
Previously `TRUNCATE TABLE ... PARTITION` will always truncate the whole table for data source tables, this PR fixes it and improve `InMemoryCatalog` to make this command work with it.
## How was this patch tested?
existing tests
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15688 from cloud-fan/truncate.
## What changes were proposed in this pull request?
This PR proposes `rand`/`randn` accept `null` as input in Scala/SQL and `LongType` as input in SQL. In this case, it treats the values as `0`.
So, this PR includes both changes below:
- `null` support
It seems MySQL also accepts this.
``` sql
mysql> select rand(0);
+---------------------+
| rand(0) |
+---------------------+
| 0.15522042769493574 |
+---------------------+
1 row in set (0.00 sec)
mysql> select rand(NULL);
+---------------------+
| rand(NULL) |
+---------------------+
| 0.15522042769493574 |
+---------------------+
1 row in set (0.00 sec)
```
and also Hive does according to [HIVE-14694](https://issues.apache.org/jira/browse/HIVE-14694)
So the codes below:
``` scala
spark.range(1).selectExpr("rand(null)").show()
```
prints..
**Before**
```
Input argument to rand must be an integer literal.;; line 1 pos 0
org.apache.spark.sql.AnalysisException: Input argument to rand must be an integer literal.;; line 1 pos 0
at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:465)
at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:444)
```
**After**
```
+-----------------------+
|rand(CAST(NULL AS INT))|
+-----------------------+
| 0.13385709732307427|
+-----------------------+
```
- `LongType` support in SQL.
In addition, it make the function allows to take `LongType` consistently within Scala/SQL.
In more details, the codes below:
``` scala
spark.range(1).select(rand(1), rand(1L)).show()
spark.range(1).selectExpr("rand(1)", "rand(1L)").show()
```
prints..
**Before**
```
+------------------+------------------+
| rand(1)| rand(1)|
+------------------+------------------+
|0.2630967864682161|0.2630967864682161|
+------------------+------------------+
Input argument to rand must be an integer literal.;; line 1 pos 0
org.apache.spark.sql.AnalysisException: Input argument to rand must be an integer literal.;; line 1 pos 0
at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:465)
at
```
**After**
```
+------------------+------------------+
| rand(1)| rand(1)|
+------------------+------------------+
|0.2630967864682161|0.2630967864682161|
+------------------+------------------+
+------------------+------------------+
| rand(1)| rand(1)|
+------------------+------------------+
|0.2630967864682161|0.2630967864682161|
+------------------+------------------+
```
## How was this patch tested?
Unit tests in `DataFrameSuite.scala` and `RandomSuite.scala`.
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#15432 from HyukjinKwon/SPARK-17854.
## What changes were proposed in this pull request?
Prior this pr, the following code would cause an NPE:
`case class point(a:String, b:String, c:String, d: Int)`
`val data = Seq(
point("1","2","3", 1),
point("4","5","6", 1),
point("7","8","9", 1)
)`
`sc.parallelize(data).toDF().registerTempTable("table")`
`spark.sql("select a, b, c, count(d) from table group by a, b, c GROUPING SETS ((a)) ").show()`
The reason is that when the grouping_id() behavior was changed in #10677, some code (which should be changed) was left out.
Take the above code for example, prior #10677, the bit mask for set "(a)" was `001`, while after #10677 the bit mask was changed to `011`. However, the `nonNullBitmask` was not changed accordingly.
This pr will fix this problem.
## How was this patch tested?
add integration tests
Author: wangyang <wangyang@haizhi.com>
Closes#15416 from yangw1234/groupingid.
## What changes were proposed in this pull request?
As the title suggests, this patch moves hash expressions from misc.scala into hash.scala, to make it easier to find the hash functions. I wanted to do this a while ago but decided to wait for the branch-2.1 cut so the chance of conflicts will be smaller.
## How was this patch tested?
Test cases were also moved out of MiscFunctionsSuite into HashExpressionsSuite.
Author: Reynold Xin <rxin@databricks.com>
Closes#15784 from rxin/SPARK-18287.
## What changes were proposed in this pull request?
For data source tables, we will put its table schema, partition columns, etc. to table properties, to work around some hive metastore issues, e.g. not case-preserving, bad decimal type support, etc.
We should also do this for hive serde tables, to reduce the difference between hive serde tables and data source tables, e.g. column names should be case preserving.
## How was this patch tested?
existing tests, and a new test in `HiveExternalCatalog`
Author: Wenchen Fan <wenchen@databricks.com>
Closes#14750 from cloud-fan/minor1.
## What changes were proposed in this pull request?
`from_json` is currently not safe against `null` rows. This PR adds a fix and a regression test for it.
## How was this patch tested?
Regression test
Author: Burak Yavuz <brkyvz@gmail.com>
Closes#15771 from brkyvz/json_fix.
## What changes were proposed in this pull request?
The `PushDownPredicate` rule can create a wrong result if we try to push a filter containing a predicate subquery through a project when the subquery and the project share attributes (have the same source).
The current PR fixes this by making sure that we do not push down when there is a predicate subquery that outputs the same attributes as the filters new child plan.
## How was this patch tested?
Added a test to `SubquerySuite`. nsyca has done previous work this. I have taken test from his initial PR.
Author: Herman van Hovell <hvanhovell@databricks.com>
Closes#15761 from hvanhovell/SPARK-17337.
## What changes were proposed in this pull request?
This patch renames partitionProviderIsHive to tracksPartitionsInCatalog, as the old name was too Hive specific.
## How was this patch tested?
Should be covered by existing tests.
Author: Reynold Xin <rxin@databricks.com>
Closes#15750 from rxin/SPARK-18244.
## What changes were proposed in this pull request?
I was reading this part of the code and was really confused by the "partition" parameter. This patch adds some documentation for it to reduce confusion in the future.
I also looked around other logical plans but most of them are either already documented, or pretty self-evident to people that know Spark SQL.
## How was this patch tested?
N/A - doc change only.
Author: Reynold Xin <rxin@databricks.com>
Closes#15749 from rxin/doc-improvement.
## What changes were proposed in this pull request?
In Spark 1.6 and earlier, we can drop the database we are using. In Spark 2.0, native implementation prevent us from dropping current database, which may break some old queries. This PR would re-enable the feature.
## How was this patch tested?
one new unit test in `SessionCatalogSuite`.
Author: Daoyuan Wang <daoyuan.wang@intel.com>
Closes#15011 from adrian-wang/dropcurrent.
### What changes were proposed in this pull request?
So far, we have limited test case coverage about implicit type casting. We need to draw a matrix to find all the possible casting pairs.
- Reorged the existing test cases
- Added all the possible type casting pairs
- Drawed a matrix to show the implicit type casting. The table is very wide. Maybe hard to review. Thus, you also can access the same table via the link to [a google sheet](https://docs.google.com/spreadsheets/d/19PS4ikrs-Yye_mfu-rmIKYGnNe-NmOTt5DDT1fOD3pI/edit?usp=sharing).
SourceType\CastToType | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | BinaryType | BooleanType | StringType | DateType | TimestampType | ArrayType | MapType | StructType | NullType | CalendarIntervalType | DecimalType | NumericType | IntegralType
------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | -----------
**ByteType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(3, 0) | ByteType | ByteType
**ShortType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(5, 0) | ShortType | ShortType
**IntegerType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(10, 0) | IntegerType | IntegerType
**LongType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(20, 0) | LongType | LongType
**DoubleType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(30, 15) | DoubleType | IntegerType
**FloatType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(14, 7) | FloatType | IntegerType
**Dec(10, 2)** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | X | X | StringType | X | X | X | X | X | X | X | DecimalType(10, 2) | Dec(10, 2) | IntegerType
**BinaryType** | X | X | X | X | X | X | X | BinaryType | X | StringType | X | X | X | X | X | X | X | X | X | X
**BooleanType** | X | X | X | X | X | X | X | X | BooleanType | StringType | X | X | X | X | X | X | X | X | X | X
**StringType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | BinaryType | X | StringType | DateType | TimestampType | X | X | X | X | X | DecimalType(38, 18) | DoubleType | X
**DateType** | X | X | X | X | X | X | X | X | X | StringType | DateType | TimestampType | X | X | X | X | X | X | X | X
**TimestampType** | X | X | X | X | X | X | X | X | X | StringType | DateType | TimestampType | X | X | X | X | X | X | X | X
**ArrayType** | X | X | X | X | X | X | X | X | X | X | X | X | ArrayType* | X | X | X | X | X | X | X
**MapType** | X | X | X | X | X | X | X | X | X | X | X | X | X | MapType* | X | X | X | X | X | X
**StructType** | X | X | X | X | X | X | X | X | X | X | X | X | X | X | StructType* | X | X | X | X | X
**NullType** | ByteType | ShortType | IntegerType | LongType | DoubleType | FloatType | Dec(10, 2) | BinaryType | BooleanType | StringType | DateType | TimestampType | ArrayType | MapType | StructType | NullType | CalendarIntervalType | DecimalType(38, 18) | DoubleType | IntegerType
**CalendarIntervalType** | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | CalendarIntervalType | X | X | X
Note: ArrayType\*, MapType\*, StructType\* are castable only when the internal child types also match; otherwise, not castable
### How was this patch tested?
N/A
Author: gatorsmile <gatorsmile@gmail.com>
Closes#15691 from gatorsmile/implicitTypeCasting.
## What changes were proposed in this pull request?
This PR proposes to change the documentation for functions. Please refer the discussion from https://github.com/apache/spark/pull/15513
The changes include
- Re-indent the documentation
- Add examples/arguments in `extended` where the arguments are multiple or specific format (e.g. xml/ json).
For examples, the documentation was updated as below:
### Functions with single line usage
**Before**
- `pow`
``` sql
Usage: pow(x1, x2) - Raise x1 to the power of x2.
Extended Usage:
> SELECT pow(2, 3);
8.0
```
- `current_timestamp`
``` sql
Usage: current_timestamp() - Returns the current timestamp at the start of query evaluation.
Extended Usage:
No example for current_timestamp.
```
**After**
- `pow`
``` sql
Usage: pow(expr1, expr2) - Raises `expr1` to the power of `expr2`.
Extended Usage:
Examples:
> SELECT pow(2, 3);
8.0
```
- `current_timestamp`
``` sql
Usage: current_timestamp() - Returns the current timestamp at the start of query evaluation.
Extended Usage:
No example/argument for current_timestamp.
```
### Functions with (already) multiple line usage
**Before**
- `approx_count_distinct`
``` sql
Usage: approx_count_distinct(expr) - Returns the estimated cardinality by HyperLogLog++.
approx_count_distinct(expr, relativeSD=0.05) - Returns the estimated cardinality by HyperLogLog++
with relativeSD, the maximum estimation error allowed.
Extended Usage:
No example for approx_count_distinct.
```
- `percentile_approx`
``` sql
Usage:
percentile_approx(col, percentage [, accuracy]) - Returns the approximate percentile value of numeric
column `col` at the given percentage. The value of percentage must be between 0.0
and 1.0. The `accuracy` parameter (default: 10000) is a positive integer literal which
controls approximation accuracy at the cost of memory. Higher value of `accuracy` yields
better accuracy, `1.0/accuracy` is the relative error of the approximation.
percentile_approx(col, array(percentage1 [, percentage2]...) [, accuracy]) - Returns the approximate
percentile array of column `col` at the given percentage array. Each value of the
percentage array must be between 0.0 and 1.0. The `accuracy` parameter (default: 10000) is
a positive integer literal which controls approximation accuracy at the cost of memory.
Higher value of `accuracy` yields better accuracy, `1.0/accuracy` is the relative error of
the approximation.
Extended Usage:
No example for percentile_approx.
```
**After**
- `approx_count_distinct`
``` sql
Usage:
approx_count_distinct(expr[, relativeSD]) - Returns the estimated cardinality by HyperLogLog++.
`relativeSD` defines the maximum estimation error allowed.
Extended Usage:
No example/argument for approx_count_distinct.
```
- `percentile_approx`
``` sql
Usage:
percentile_approx(col, percentage [, accuracy]) - Returns the approximate percentile value of numeric
column `col` at the given percentage. The value of percentage must be between 0.0
and 1.0. The `accuracy` parameter (default: 10000) is a positive numeric literal which
controls approximation accuracy at the cost of memory. Higher value of `accuracy` yields
better accuracy, `1.0/accuracy` is the relative error of the approximation.
When `percentage` is an array, each value of the percentage array must be between 0.0 and 1.0.
In this case, returns the approximate percentile array of column `col` at the given
percentage array.
Extended Usage:
Examples:
> SELECT percentile_approx(10.0, array(0.5, 0.4, 0.1), 100);
[10.0,10.0,10.0]
> SELECT percentile_approx(10.0, 0.5, 100);
10.0
```
## How was this patch tested?
Manually tested
**When examples are multiple**
``` sql
spark-sql> describe function extended reflect;
Function: reflect
Class: org.apache.spark.sql.catalyst.expressions.CallMethodViaReflection
Usage: reflect(class, method[, arg1[, arg2 ..]]) - Calls a method with reflection.
Extended Usage:
Examples:
> SELECT reflect('java.util.UUID', 'randomUUID');
c33fb387-8500-4bfa-81d2-6e0e3e930df2
> SELECT reflect('java.util.UUID', 'fromString', 'a5cf6c42-0c85-418f-af6c-3e4e5b1328f2');
a5cf6c42-0c85-418f-af6c-3e4e5b1328f2
```
**When `Usage` is in single line**
``` sql
spark-sql> describe function extended min;
Function: min
Class: org.apache.spark.sql.catalyst.expressions.aggregate.Min
Usage: min(expr) - Returns the minimum value of `expr`.
Extended Usage:
No example/argument for min.
```
**When `Usage` is already in multiple lines**
``` sql
spark-sql> describe function extended percentile_approx;
Function: percentile_approx
Class: org.apache.spark.sql.catalyst.expressions.aggregate.ApproximatePercentile
Usage:
percentile_approx(col, percentage [, accuracy]) - Returns the approximate percentile value of numeric
column `col` at the given percentage. The value of percentage must be between 0.0
and 1.0. The `accuracy` parameter (default: 10000) is a positive numeric literal which
controls approximation accuracy at the cost of memory. Higher value of `accuracy` yields
better accuracy, `1.0/accuracy` is the relative error of the approximation.
When `percentage` is an array, each value of the percentage array must be between 0.0 and 1.0.
In this case, returns the approximate percentile array of column `col` at the given
percentage array.
Extended Usage:
Examples:
> SELECT percentile_approx(10.0, array(0.5, 0.4, 0.1), 100);
[10.0,10.0,10.0]
> SELECT percentile_approx(10.0, 0.5, 100);
10.0
```
**When example/argument is missing**
``` sql
spark-sql> describe function extended rank;
Function: rank
Class: org.apache.spark.sql.catalyst.expressions.Rank
Usage:
rank() - Computes the rank of a value in a group of values. The result is one plus the number
of rows preceding or equal to the current row in the ordering of the partition. The values
will produce gaps in the sequence.
Extended Usage:
No example/argument for rank.
```
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#15677 from HyukjinKwon/SPARK-17963-1.
## What changes were proposed in this pull request?
Due to a limitation of hive metastore(table location must be directory path, not file path), we always store `path` for data source table in storage properties, instead of the `locationUri` field. However, we should not expose this difference to `CatalogTable` level, but just treat it as a hack in `HiveExternalCatalog`, like we store table schema of data source table in table properties.
This PR unifies `path` and `locationUri` outside of `HiveExternalCatalog`, both data source table and hive serde table should use the `locationUri` field.
This PR also unifies the way we handle default table location for managed table. Previously, the default table location of hive serde managed table is set by external catalog, but the one of data source table is set by command. After this PR, we follow the hive way and the default table location is always set by external catalog.
For managed non-file-based tables, we will assign a default table location and create an empty directory for it, the table location will be removed when the table is dropped. This is reasonable as metastore doesn't care about whether a table is file-based or not, and an empty table directory has no harm.
For external non-file-based tables, ideally we can omit the table location, but due to a hive metastore issue, we will assign a random location to it, and remove it right after the table is created. See SPARK-15269 for more details. This is fine as it's well isolated in `HiveExternalCatalog`.
To keep the existing behaviour of the `path` option, in this PR we always add the `locationUri` to storage properties using key `path`, before passing storage properties to `DataSource` as data source options.
## How was this patch tested?
existing tests.
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15024 from cloud-fan/path.
## What changes were proposed in this pull request?
RuntimeReplaceable is used to create aliases for expressions, but the way it deals with type coercion is pretty weird (each expression is responsible for how to handle type coercion, which does not obey the normal implicit type cast rules).
This patch simplifies its handling by allowing the analyzer to traverse into the actual expression of a RuntimeReplaceable.
## How was this patch tested?
- Correctness should be guaranteed by existing unit tests already
- Removed SQLCompatibilityFunctionSuite and moved it sql-compatibility-functions.sql
- Added a new test case in sql-compatibility-functions.sql for verifying explain behavior.
Author: Reynold Xin <rxin@databricks.com>
Closes#15723 from rxin/SPARK-18214.
## What changes were proposed in this pull request?
When a user appended a column using a "nondeterministic" function to a DataFrame, e.g., `rand`, `randn`, and `monotonically_increasing_id`, the expected semantic is the following:
- The value in each row should remain unchanged, as if we materialize the column immediately, regardless of later DataFrame operations.
However, since we use `TaskContext.getPartitionId` to get the partition index from the current thread, the values from nondeterministic columns might change if we call `union` or `coalesce` after. `TaskContext.getPartitionId` returns the partition index of the current Spark task, which might not be the corresponding partition index of the DataFrame where we defined the column.
See the unit tests below or JIRA for examples.
This PR uses the partition index from `RDD.mapPartitionWithIndex` instead of `TaskContext` and fixes the partition initialization logic in whole-stage codegen, normal codegen, and codegen fallback. `initializeStatesForPartition(partitionIndex: Int)` was added to `Projection`, `Nondeterministic`, and `Predicate` (codegen) and initialized right after object creation in `mapPartitionWithIndex`. `newPredicate` now returns a `Predicate` instance rather than a function for proper initialization.
## How was this patch tested?
Unit tests. (Actually I'm not very confident that this PR fixed all issues without introducing new ones ...)
cc: rxin davies
Author: Xiangrui Meng <meng@databricks.com>
Closes#15567 from mengxr/SPARK-14393.
## What changes were proposed in this pull request?
This pr is to add pattern-matching entries for array data in `Literal.apply`.
## How was this patch tested?
Added tests in `LiteralExpressionSuite`.
Author: Takeshi YAMAMURO <linguin.m.s@gmail.com>
Closes#15257 from maropu/SPARK-17683.
## What changes were proposed in this pull request?
Simplify struct creation, especially the aspect of `CleanupAliases` which missed some aliases when handling trees created by `CreateStruct`.
This PR includes:
1. A failing test (create struct with nested aliases, some of the aliases survive `CleanupAliases`).
2. A fix that transforms `CreateStruct` into a `CreateNamedStruct` constructor, effectively eliminating `CreateStruct` from all expression trees.
3. A `NamePlaceHolder` used by `CreateStruct` when column names cannot be extracted from unresolved `NamedExpression`.
4. A new Analyzer rule that resolves `NamePlaceHolder` into a string literal once the `NamedExpression` is resolved.
5. `CleanupAliases` code was simplified as it no longer has to deal with `CreateStruct`'s top level columns.
## How was this patch tested?
Running all tests-suits in package org.apache.spark.sql, especially including the analysis suite, making sure added test initially fails, after applying suggested fix rerun the entire analysis package successfully.
Modified few tests that expected `CreateStruct` which is now transformed into `CreateNamedStruct`.
Author: eyal farago <eyal farago>
Author: Herman van Hovell <hvanhovell@databricks.com>
Author: eyal farago <eyal.farago@gmail.com>
Author: Eyal Farago <eyal.farago@actimize.com>
Author: Hyukjin Kwon <gurwls223@gmail.com>
Author: eyalfa <eyal.farago@gmail.com>
Closes#15718 from hvanhovell/SPARK-16839-2.
## What changes were proposed in this pull request?
Fix `Locale.US` for all usages of `DateFormat`, `NumberFormat`
## How was this patch tested?
Existing tests.
Author: Sean Owen <sowen@cloudera.com>
Closes#15610 from srowen/SPARK-18076.
## What changes were proposed in this pull request?
There are a couple issues with the current 2.1 behavior when inserting into Datasource tables with partitions managed by Hive.
(1) OVERWRITE TABLE ... PARTITION will actually overwrite the entire table instead of just the specified partition.
(2) INSERT|OVERWRITE does not work with partitions that have custom locations.
This PR fixes both of these issues for Datasource tables managed by Hive. The behavior for legacy tables or when `manageFilesourcePartitions = false` is unchanged.
There is one other issue in that INSERT OVERWRITE with dynamic partitions will overwrite the entire table instead of just the updated partitions, but this behavior is pretty complicated to implement for Datasource tables. We should address that in a future release.
## How was this patch tested?
Unit tests.
Author: Eric Liang <ekl@databricks.com>
Closes#15705 from ericl/sc-4942.
## What changes were proposed in this pull request?
This PR proposes to add `to_json` function in contrast with `from_json` in Scala, Java and Python.
It'd be useful if we can convert a same column from/to json. Also, some datasources do not support nested types. If we are forced to save a dataframe into those data sources, we might be able to work around by this function.
The usage is as below:
``` scala
val df = Seq(Tuple1(Tuple1(1))).toDF("a")
df.select(to_json($"a").as("json")).show()
```
``` bash
+--------+
| json|
+--------+
|{"_1":1}|
+--------+
```
## How was this patch tested?
Unit tests in `JsonFunctionsSuite` and `JsonExpressionsSuite`.
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#15354 from HyukjinKwon/SPARK-17764.
## What changes were proposed in this pull request?
Aggregation Without Window/GroupBy expressions will fail in `checkAnalysis`, the error message is a bit misleading, we should generate a more specific error message for this case.
For example,
```
spark.read.load("/some-data")
.withColumn("date_dt", to_date($"date"))
.withColumn("year", year($"date_dt"))
.withColumn("week", weekofyear($"date_dt"))
.withColumn("user_count", count($"userId"))
.withColumn("daily_max_in_week", max($"user_count").over(weeklyWindow))
)
```
creates the following output:
```
org.apache.spark.sql.AnalysisException: expression '`randomColumn`' is neither present in the group by, nor is it an aggregate function. Add to group by or wrap in first() (or first_value) if you don't care which value you get.;
```
In the error message above, `randomColumn` doesn't appear in the query(acturally it's added by function `withColumn`), so the message is not enough for the user to address the problem.
## How was this patch tested?
Manually test
Before:
```
scala> spark.sql("select col, count(col) from tbl")
org.apache.spark.sql.AnalysisException: expression 'tbl.`col`' is neither present in the group by, nor is it an aggregate function. Add to group by or wrap in first() (or first_value) if you don't care which value you get.;;
```
After:
```
scala> spark.sql("select col, count(col) from tbl")
org.apache.spark.sql.AnalysisException: grouping expressions sequence is empty, and 'tbl.`col`' is not an aggregate function. Wrap '(count(col#231L) AS count(col)#239L)' in windowing function(s) or wrap 'tbl.`col`' in first() (or first_value) if you don't care which value you get.;;
```
Also add new test sqls in `group-by.sql`.
Author: jiangxingbo <jiangxb1987@gmail.com>
Closes#15672 from jiangxb1987/groupBy-empty.
## What changes were proposed in this pull request?
Simplify struct creation, especially the aspect of `CleanupAliases` which missed some aliases when handling trees created by `CreateStruct`.
This PR includes:
1. A failing test (create struct with nested aliases, some of the aliases survive `CleanupAliases`).
2. A fix that transforms `CreateStruct` into a `CreateNamedStruct` constructor, effectively eliminating `CreateStruct` from all expression trees.
3. A `NamePlaceHolder` used by `CreateStruct` when column names cannot be extracted from unresolved `NamedExpression`.
4. A new Analyzer rule that resolves `NamePlaceHolder` into a string literal once the `NamedExpression` is resolved.
5. `CleanupAliases` code was simplified as it no longer has to deal with `CreateStruct`'s top level columns.
## How was this patch tested?
running all tests-suits in package org.apache.spark.sql, especially including the analysis suite, making sure added test initially fails, after applying suggested fix rerun the entire analysis package successfully.
modified few tests that expected `CreateStruct` which is now transformed into `CreateNamedStruct`.
Credit goes to hvanhovell for assisting with this PR.
Author: eyal farago <eyal farago>
Author: eyal farago <eyal.farago@gmail.com>
Author: Herman van Hovell <hvanhovell@databricks.com>
Author: Eyal Farago <eyal.farago@actimize.com>
Author: Hyukjin Kwon <gurwls223@gmail.com>
Author: eyalfa <eyal.farago@gmail.com>
Closes#14444 from eyalfa/SPARK-16839_redundant_aliases_after_cleanupAliases.
## What changes were proposed in this pull request?
Currently an unqualified `getFunction(..)`call returns a wrong result; the returned function is shown as temporary function without a database. For example:
```
scala> sql("create function fn1 as 'org.apache.hadoop.hive.ql.udf.generic.GenericUDFAbs'")
res0: org.apache.spark.sql.DataFrame = []
scala> spark.catalog.getFunction("fn1")
res1: org.apache.spark.sql.catalog.Function = Function[name='fn1', className='org.apache.hadoop.hive.ql.udf.generic.GenericUDFAbs', isTemporary='true']
```
This PR fixes this by adding database information to ExpressionInfo (which is used to store the function information).
## How was this patch tested?
Added more thorough tests to `CatalogSuite`.
Author: Herman van Hovell <hvanhovell@databricks.com>
Closes#15542 from hvanhovell/SPARK-17996.
## What changes were proposed in this pull request?
When multiple records have the minimum value, the answer of ApproximatePercentile is wrong.
## How was this patch tested?
add a test case
Author: wangzhenhua <wangzhenhua@huawei.com>
Closes#15641 from wzhfy/percentile.
## What changes were proposed in this pull request?
We should follow hive table and also store partition spec in metastore for data source table.
This brings 2 benefits:
1. It's more flexible to manage the table data files, as users can use `ADD PARTITION`, `DROP PARTITION` and `RENAME PARTITION`
2. We don't need to cache all file status for data source table anymore.
## How was this patch tested?
existing tests.
Author: Eric Liang <ekl@databricks.com>
Author: Michael Allman <michael@videoamp.com>
Author: Eric Liang <ekhliang@gmail.com>
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15515 from cloud-fan/partition.
## What changes were proposed in this pull request?
In order to facilitate the writing of additional Encoders, I proposed opening up the ObjectType SQL DataType. This DataType is used extensively in the JavaBean Encoder, but would also be useful in writing other custom encoders.
As mentioned by marmbrus, it is understood that the Expressions API is subject to potential change.
## How was this patch tested?
The change only affects the visibility of the ObjectType class, and the existing SQL test suite still runs without error.
Author: ALeksander Eskilson <alek.eskilson@cerner.com>
Closes#15453 from bdrillard/master.
## What changes were proposed in this pull request?
The `UnaryNode.getAliasedConstraints` function fails to replace all expressions by their alias where constraints contains more than one expression to be replaced.
For example:
```
val tr = LocalRelation('a.int, 'b.string, 'c.int)
val multiAlias = tr.where('a === 'c + 10).select('a.as('x), 'c.as('y))
multiAlias.analyze.constraints
```
currently outputs:
```
ExpressionSet(Seq(
IsNotNull(resolveColumn(multiAlias.analyze, "x")),
IsNotNull(resolveColumn(multiAlias.analyze, "y"))
)
```
The constraint `resolveColumn(multiAlias.analyze, "x") === resolveColumn(multiAlias.analyze, "y") + 10)` is missing.
## How was this patch tested?
Add new test cases in `ConstraintPropagationSuite`.
Author: jiangxingbo <jiangxb1987@gmail.com>
Closes#15597 from jiangxb1987/alias-constraints.
## What changes were proposed in this pull request?
The function `QueryPlan.inferAdditionalConstraints` and `UnaryNode.getAliasedConstraints` can produce a non-converging set of constraints for recursive functions. For instance, if we have two constraints of the form(where a is an alias):
`a = b, a = f(b, c)`
Applying both these rules in the next iteration would infer:
`f(b, c) = f(f(b, c), c)`
This process repeated, the iteration won't converge and the set of constraints will grow larger and larger until OOM.
~~To fix this problem, we collect alias from expressions and skip infer constraints if we are to transform an `Expression` to another which contains it.~~
To fix this problem, we apply additional check in `inferAdditionalConstraints`, when it's possible to generate recursive constraints, we skip generate that.
## How was this patch tested?
Add new testcase in `SQLQuerySuite`/`InferFiltersFromConstraintsSuite`.
Author: jiangxingbo <jiangxb1987@gmail.com>
Closes#15319 from jiangxb1987/constraints.
## What changes were proposed in this pull request?
Binary operator requires its inputs to be of same type, but it should not consider nullability, e.g. `EqualTo` should be able to compare an element-nullable array and an element-non-nullable array.
## How was this patch tested?
a regression test in `DataFrameSuite`
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15606 from cloud-fan/type-bug.
## What changes were proposed in this pull request?
Currently we always lowercase the partition columns of partition spec in parser, with the assumption that table partition columns are always lowercased.
However, this is not true for data source tables, which are case preserving. It's safe for now because data source tables don't store partition spec in metastore and don't support `ADD PARTITION`, `DROP PARTITION`, `RENAME PARTITION`, but we should make our code future-proof.
This PR makes partition spec case preserving at parser, and improve the `PreprocessTableInsertion` analyzer rule to normalize the partition columns in partition spec, w.r.t. the table partition columns.
## How was this patch tested?
existing tests.
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15566 from cloud-fan/partition-spec.
## What changes were proposed in this pull request?
Simplify/cleanup TableFileCatalog:
1. pass a `CatalogTable` instead of `databaseName` and `tableName` into `TableFileCatalog`, so that we don't need to fetch table metadata from metastore again
2. In `TableFileCatalog.filterPartitions0`, DO NOT set `PartitioningAwareFileCatalog.BASE_PATH_PARAM`. According to the [classdoc](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningAwareFileCatalog.scala#L189-L209), the default value of `basePath` already satisfies our need. What's more, if we set this parameter, we may break the case 2 which is metioned in the classdoc.
3. add `equals` and `hashCode` to `TableFileCatalog`
4. add `SessionCatalog.listPartitionsByFilter` which handles case sensitivity.
## How was this patch tested?
existing tests.
Author: Wenchen Fan <wenchen@databricks.com>
Closes#15568 from cloud-fan/table-file-catalog.
## What changes were proposed in this pull request?
The PR tries to fix [SPARK-18058](https://issues.apache.org/jira/browse/SPARK-18058) which refers to a bug that the column types are compared with the extra care about Nullability in Union and SetOperation.
This PR converts the columns types by setting all fields as nullable before comparison
## How was this patch tested?
regular unit test cases
Author: CodingCat <zhunansjtu@gmail.com>
Closes#15595 from CodingCat/SPARK-18058.
## What changes were proposed in this pull request?
Jira: https://issues.apache.org/jira/browse/SPARK-18035
In HiveInspectors, I saw that converting Java map to Spark's `ArrayBasedMapData` spent quite sometime in buffer copying : https://github.com/apache/spark/blob/master/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveInspectors.scala#L658
The reason being `map.toSeq` allocates a new buffer and copies the map entries to it: https://github.com/scala/scala/blob/2.11.x/src/library/scala/collection/MapLike.scala#L323
This copy is not needed as we get rid of it once we extract the key and value arrays.
Here is the call trace:
```
org.apache.spark.sql.hive.HiveInspectors$$anonfun$unwrapperFor$41.apply(HiveInspectors.scala:664)
scala.collection.AbstractMap.toSeq(Map.scala:59)
scala.collection.MapLike$class.toSeq(MapLike.scala:323)
scala.collection.AbstractMap.toBuffer(Map.scala:59)
scala.collection.MapLike$class.toBuffer(MapLike.scala:326)
scala.collection.AbstractTraversable.copyToBuffer(Traversable.scala:104)
scala.collection.TraversableOnce$class.copyToBuffer(TraversableOnce.scala:275)
scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:48)
scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:104)
scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:59)
scala.collection.AbstractIterable.foreach(Iterable.scala:54)
scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
scala.collection.AbstractIterator.foreach(Iterator.scala:1336)
scala.collection.Iterator$class.foreach(Iterator.scala:893)
scala.collection.generic.Growable$$anonfun$$plus$plus$eq$1.apply(Growable.scala:59)
scala.collection.generic.Growable$$anonfun$$plus$plus$eq$1.apply(Growable.scala:59)
```
Also, earlier code was populating keys and values arrays separately by iterating twice. The PR avoids double iteration of the map and does it in one iteration.
EDIT: During code review, there were several more places in the code which were found to do similar thing. The PR dedupes those instances and introduces convenient APIs which are performant and memory efficient
## Performance gains
The number is subjective and depends on how many map columns are accessed in the query and average entries per map. For one the queries that I tried out, I saw 3% CPU savings (end-to-end) for the query.
## How was this patch tested?
This does not change the end result produced so relying on existing tests.
Author: Tejas Patil <tejasp@fb.com>
Closes#15573 from tejasapatil/SPARK-18035_avoid_toSeq.
## What changes were proposed in this pull request?
`Array[T]()` -> `Array.empty[T]` to avoid allocating 0-length arrays.
Use regex `find . -name '*.scala' | xargs -i bash -c 'egrep "Array\[[A-Za-z]+\]\(\)" -n {} && echo {}'` to find modification candidates.
cc srowen
## How was this patch tested?
existing tests
Author: Zheng RuiFeng <ruifengz@foxmail.com>
Closes#15564 from zhengruifeng/avoid_0_length_array.
