Previously it was okay to throw away subqueries after analysis, as we would never try to use that tree for resolution again. However, with eager analysis in `DataFrame`s this can cause errors for queries such as:
```scala
val df = Seq(1,2,3).map(i => (i, i.toString)).toDF("int", "str")
df.as('x).join(df.as('y), $"x.str" === $"y.str").groupBy("x.str").count()
```
As a result, in this PR we defer the elimination of subqueries until the optimization phase.
Author: Michael Armbrust <michael@databricks.com>
Closes#5160 from marmbrus/subqueriesInDfs and squashes the following commits:
a9bb262 [Michael Armbrust] Update Optimizer.scala
27d25bf [Michael Armbrust] fix hive tests
9137e03 [Michael Armbrust] add type
81cd597 [Michael Armbrust] Avoid eliminating subqueries until optimization
Author: Michael Armbrust <michael@databricks.com>
Closes#5155 from marmbrus/errorMessages and squashes the following commits:
b898188 [Michael Armbrust] Fix formatting of error messages.
Due to a recent change that made `StructType` a `Seq` we started inadvertently turning `StructType`s into generic `Traversable` when attempting nested tree transformations. In this PR we explicitly avoid descending into `DataType`s to avoid this bug.
Author: Michael Armbrust <michael@databricks.com>
Closes#5157 from marmbrus/udfFix and squashes the following commits:
26f7087 [Michael Armbrust] Fix transformations of TreeNodes that hold StructTypes
This is used by ML pipelines to embed ML attributes in columns created by ML transformers/estimators. marmbrus
Author: Xiangrui Meng <meng@databricks.com>
Closes#5151 from mengxr/SPARK-6361 and squashes the following commits:
bb30de3 [Xiangrui Meng] support adding a column with metadata in DF
In `CheckAnalysis`, `Filter` and `Aggregate` are checked in separate case clauses, thus never hit those clauses for unresolved operators and missing input attributes.
This PR also removes the `prettyString` call when generating error message for missing input attributes. Because result of `prettyString` doesn't contain expression ID, and may give confusing messages like
> resolved attributes a missing from a
cc rxin
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Author: Cheng Lian <lian@databricks.com>
Closes#5129 from liancheng/spark-6452 and squashes the following commits:
52cdc69 [Cheng Lian] Addresses comments
029f9bd [Cheng Lian] Checks for missing attributes and unresolved operator for all types of operator
https://github.com/apache/spark/pull/5082
/cc liancheng
Author: Yadong Qi <qiyadong2010@gmail.com>
Closes#5132 from watermen/sql-missingInput-new and squashes the following commits:
1e5bdc5 [Yadong Qi] Check the missingInput simply
Author: q00251598 <qiyadong@huawei.com>
Closes#5082 from watermen/sql-missingInput and squashes the following commits:
25766b9 [q00251598] Check the missingInput simply
This PR creates a trait `DataTypeParser` used to parse data types. This trait aims to be single place to provide the functionality of parsing data types' string representation. It is currently mixed in with `DDLParser` and `SqlParser`. It is also used to parse the data type for `DataFrame.cast` and to convert Hive metastore's data type string back to a `DataType`.
JIRA: https://issues.apache.org/jira/browse/SPARK-6250
Author: Yin Huai <yhuai@databricks.com>
Closes#5078 from yhuai/ddlKeywords and squashes the following commits:
0e66097 [Yin Huai] Special handle struct<>.
fea6012 [Yin Huai] Style.
c9733fb [Yin Huai] Create a trait to parse data types.
SELECT sum('a'), avg('a'), variance('a'), std('a') FROM src;
Should give output as
0.0 NULL NULL NULL
This fixes hive udaf_number_format.q
Author: Venkata Ramana G <ramana.gollamudihuawei.com>
Author: Venkata Ramana Gollamudi <ramana.gollamudi@huawei.com>
Closes#4466 from gvramana/sum_fix and squashes the following commits:
42e14d1 [Venkata Ramana Gollamudi] Added comments
39415c0 [Venkata Ramana Gollamudi] Handled the partitioned Sum expression scenario
df66515 [Venkata Ramana Gollamudi] code style fix
4be2606 [Venkata Ramana Gollamudi] Add udaf_number_format to whitelist and golden answer
330fd64 [Venkata Ramana Gollamudi] fix sum function for all null data
Because of no statistics override, in spute of super class say 'LeafNode must override'.
fix issue
[SPARK-5320: Joins on simple table created using select gives error](https://issues.apache.org/jira/browse/SPARK-5320)
Author: x1- <viva008@gmail.com>
Closes#5105 from x1-/SPARK-5320 and squashes the following commits:
e561aac [x1-] Add statistics method at NoRelation (override super).
Also implemented equals/hashCode when they are missing.
This is done in order to enable automatic public method type checking.
Author: Reynold Xin <rxin@databricks.com>
Closes#5104 from rxin/sql-hashcode-explicittype and squashes the following commits:
ffce6f3 [Reynold Xin] Code review feedback.
8b36733 [Reynold Xin] [SPARK-6428][SQL] Added explicit type for all public methods.
Use `Utils.createTempDir()` to replace other temp file mechanisms used in some tests, to further ensure they are cleaned up, and simplify
Author: Sean Owen <sowen@cloudera.com>
Closes#5029 from srowen/SPARK-6338 and squashes the following commits:
27b740a [Sean Owen] Fix hive-thriftserver tests that don't expect an existing dir
4a212fa [Sean Owen] Standardize a bit more temp dir management
9004081 [Sean Owen] Revert some added recursive-delete calls
57609e4 [Sean Owen] Use Utils.createTempDir() to replace other temp file mechanisms used in some tests, to further ensure they are cleaned up, and simplify
We need to handle ambiguous `exprId`s that are produced by new aliases as well as those caused by leaf nodes (`MultiInstanceRelation`).
Attempting to fix this revealed a bug in `equals` for `Alias` as these objects were comparing equal even when the expression ids did not match. Additionally, `LocalRelation` did not correctly provide statistics, and some tests in `catalyst` and `hive` were not using the helper functions for comparing plans.
Based on #4991 by chenghao-intel
Author: Michael Armbrust <michael@databricks.com>
Closes#5062 from marmbrus/selfJoins and squashes the following commits:
8e9b84b [Michael Armbrust] check qualifier too
8038a36 [Michael Armbrust] handle aggs too
0b9c687 [Michael Armbrust] fix more tests
c3c574b [Michael Armbrust] revert change.
725f1ab [Michael Armbrust] add statistics
a925d08 [Michael Armbrust] check for conflicting attributes in join resolution
b022ef7 [Michael Armbrust] Handle project aliases.
d8caa40 [Michael Armbrust] test case: SPARK-6247
f9c67c2 [Michael Armbrust] Check for duplicate attributes in join resolution.
898af73 [Michael Armbrust] Fix Alias equality.
By default, the statistic for logical plan with multiple children is quite aggressive, and those statistic are quite critical for the join optimization, hence we need to estimate the statistics as accurate as possible.
For `Union`, which has 2 children, and overwrite the default implementation by `adding` its children `byteInSize` instead of `multiplying`.
For `Expand`, which only has a single child, but it will grows the size, and we need to multiply its inflating factor.
Author: Cheng Hao <hao.cheng@intel.com>
Closes#4914 from chenghao-intel/statistic and squashes the following commits:
d466bbc [Cheng Hao] Update the default statistic
use prettyString instead of toString() (which include id of expression) as column name in agg()
Author: Davies Liu <davies@databricks.com>
Closes#5006 from davies/prettystring and squashes the following commits:
cb1fdcf [Davies Liu] use prettyString as column name in agg()
Removed an repeated "from" in the comments.
Author: Hongbo Liu <liuhb86@gmail.com>
Closes#4976 from liuhb86/mine and squashes the following commits:
e280e7c [Hongbo Liu] [SQL][Minor] fix typo in comments
The extra blank line is preventing the first lines from showing up in the package summary page.
Author: Reynold Xin <rxin@databricks.com>
Closes#4955 from rxin/datatype-docs and squashes the following commits:
1621114 [Reynold Xin] Minor doc: Remove the extra blank line in data types javadoc.
Based on #4904 with style errors fixed.
`LogicalPlan#resolve` will not only produce `Attribute`, but also "`GetField` chain".
So in `ResolveSortReferences`, after resolve the ordering expressions, we should not just collect the `Attribute` results, but also `Attribute` at the bottom of "`GetField` chain".
Author: Wenchen Fan <cloud0fan@outlook.com>
Author: Michael Armbrust <michael@databricks.com>
Closes#4918 from marmbrus/pr/4904 and squashes the following commits:
997f84e [Michael Armbrust] fix style
3eedbfc [Wenchen Fan] fix 6145
Option 1 of 2: Convert spark-parent module name to spark-parent_2.10 / spark-parent_2.11
Author: Sean Owen <sowen@cloudera.com>
Closes#4912 from srowen/SPARK-6182.1 and squashes the following commits:
eff60de [Sean Owen] Convert spark-parent module name to spark-parent_2.10 / spark-parent_2.11
In `CodeGenerator`, the casting on `FloatType` should use `FloatType` instead of `IntegerType`.
Besides, `defaultPrimitive` for `LongType` should be `-1L` instead of `1L`.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#4870 from viirya/codegen_type and squashes the following commits:
76311dd [Liang-Chi Hsieh] Fix wrong datatype for casting on FloatType. Fix the wrong value for LongType in defaultPrimitive.
This PR contains the following changes:
1. Add a new method, `DataType.equalsIgnoreCompatibleNullability`, which is the middle ground between DataType's equality check and `DataType.equalsIgnoreNullability`. For two data types `from` and `to`, it does `equalsIgnoreNullability` as well as if the nullability of `from` is compatible with that of `to`. For example, the nullability of `ArrayType(IntegerType, containsNull = false)` is compatible with that of `ArrayType(IntegerType, containsNull = true)` (for an array without null values, we can always say it may contain null values). However, the nullability of `ArrayType(IntegerType, containsNull = true)` is incompatible with that of `ArrayType(IntegerType, containsNull = false)` (for an array that may have null values, we cannot say it does not have null values).
2. For the `resolved` field of `InsertIntoTable`, use `equalsIgnoreCompatibleNullability` to replace the equality check of the data types.
3. For our data source write path, when appending data, we always use the schema of existing table to write the data. This is important for parquet, since nullability direct impacts the way to encode/decode values. If we do not do this, we may see corrupted values when reading values from a set of parquet files generated with different nullability settings.
4. When generating a new parquet table, we always set nullable/containsNull/valueContainsNull to true. So, we will not face situations that we cannot append data because containsNull/valueContainsNull in an Array/Map column of the existing table has already been set to `false`. This change makes the whole data pipeline more robust.
5. Update the equality check of JSON relation. Since JSON does not really cares nullability, `equalsIgnoreNullability` seems a better choice to compare schemata from to JSON tables.
JIRA: https://issues.apache.org/jira/browse/SPARK-5950
Thanks viirya for the initial work in #4729.
cc marmbrus liancheng
Author: Yin Huai <yhuai@databricks.com>
Closes#4826 from yhuai/insertNullabilityCheck and squashes the following commits:
3b61a04 [Yin Huai] Revert change on equals.
80e487e [Yin Huai] asNullable in UDT.
587d88b [Yin Huai] Make methods private.
0cb7ea2 [Yin Huai] marmbrus's comments.
3cec464 [Yin Huai] Cheng's comments.
486ed08 [Yin Huai] Merge remote-tracking branch 'upstream/master' into insertNullabilityCheck
d3747d1 [Yin Huai] Remove unnecessary change.
8360817 [Yin Huai] Merge remote-tracking branch 'upstream/master' into insertNullabilityCheck
8a3f237 [Yin Huai] Use equalsIgnoreNullability instead of equality check.
0eb5578 [Yin Huai] Fix tests.
f6ed813 [Yin Huai] Update old parquet path.
e4f397c [Yin Huai] Unit tests.
b2c06f8 [Yin Huai] Ignore nullability in JSON relation's equality check.
8bd008b [Yin Huai] nullable, containsNull, and valueContainsNull will be always true for parquet data.
bf50d73 [Yin Huai] When appending data, we use the schema of the existing table instead of the schema of the new data.
0a703e7 [Yin Huai] Test failed again since we cannot read correct content.
9a26611 [Yin Huai] Make InsertIntoTable happy.
8f19fe5 [Yin Huai] equalsIgnoreCompatibleNullability
4ec17fd [Yin Huai] Failed test.
It should be `true` instead of `false`?
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#4762 from viirya/doc_fix and squashes the following commits:
2e37482 [Liang-Chi Hsieh] Fix doc.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#4760 from viirya/dup_literal and squashes the following commits:
06e7516 [Liang-Chi Hsieh] Remove duplicate Literal matching block.
Author: Michael Armbrust <michael@databricks.com>
Closes#4736 from marmbrus/asExprs and squashes the following commits:
5ba97e4 [Michael Armbrust] [SPARK-5910][SQL] Support for as in selectExpr
https://issues.apache.org/jira/browse/SPARK-5875 has a case to reproduce the bug and explain the root cause.
Author: Yin Huai <yhuai@databricks.com>
Closes#4663 from yhuai/projectResolved and squashes the following commits:
472f7b6 [Yin Huai] If a logical.Project has any AggregateExpression or Generator, it's resolved field should be false.
Author: Reynold Xin <rxin@databricks.com>
Closes#4640 from rxin/SPARK-5853 and squashes the following commits:
9c6f569 [Reynold Xin] [SPARK-5853][SQL] Schema support in Row.
Existing implementation of arithmetic operators and BinaryComparison operators have redundant type checking codes, e.g.:
Expression.n2 is used by Add/Subtract/Multiply.
(1) n2 always checks left.dataType == right.dataType. However, this checking should be done once when we resolve expression types;
(2) n2 requires dataType is a NumericType. This can be done once.
This PR optimizes arithmetic and predicate operators by removing such redundant type-checking codes.
Some preliminary benchmarking on 10G TPC-H data over 5 r3.2xlarge EC2 machines shows that this PR can reduce the query time by 5.5% to 11%.
The benchmark queries follow the template below, where OP is plus/minus/times/divide/remainder/bitwise and/bitwise or/bitwise xor.
SELECT l_returnflag, l_linestatus, SUM(l_quantity OP cnt1), SUM(l_quantity OP cnt2), ...., SUM(l_quantity OP cnt700)
FROM (
SELECT l_returnflag, l_linestatus, l_quantity, 1 AS cnt1, 2 AS cnt2, ..., 700 AS cnt700
FROM lineitem
WHERE l_shipdate <= '1998-09-01'
)
GROUP BY l_returnflag, l_linestatus;
Author: kai <kaizeng@eecs.berkeley.edu>
Closes#4472 from kai-zeng/arithmetic-optimize and squashes the following commits:
fef0cf1 [kai] Merge branch 'master' of github.com:apache/spark into arithmetic-optimize
4b3a1bb [kai] chmod a-x
5a41e49 [kai] chmod a-x Expression.scala
cb37c94 [kai] rebase onto spark master
7f6e968 [kai] chmod 100755 -> 100644
6cddb46 [kai] format
7490dbc [kai] fix unresolved-expression exception for EqualTo
9c40bc0 [kai] fix bitwisenot
3cbd363 [kai] clean up test code
ca47801 [kai] override evalInternal for bitwise ops
8fa84a1 [kai] add bitwise or and xor
6892fc4 [kai] revert override evalInternal
f8eba24 [kai] override evalInternal
31ccdd4 [kai] rewrite all bitwise op and remove evalInternal
86297e2 [kai] generalized
cb92ae1 [kai] bitwise-and: override eval
97a7d6c [kai] bitwise-and: override evalInternal using and func
0906c39 [kai] add bitwise test
62abbbc [kai] clean up predicate and arithmetic
b34d58d [kai] add caching and benmark option
12c5b32 [kai] override eval
1cd7571 [kai] fix sqrt and maxof
03fd0c3 [kai] fix predicate
16fd84c [kai] optimize + - * / % -(unary) abs < > <= >=
fd95823 [kai] remove unnecessary type checking
24d062f [kai] test suite
JIRA: https://issues.apache.org/jira/browse/SPARK-5746
liancheng marmbrus
Author: Yin Huai <yhuai@databricks.com>
Closes#4617 from yhuai/insertOverwrite and squashes the following commits:
8e3019d [Yin Huai] Fix compilation error.
499e8e7 [Yin Huai] Merge remote-tracking branch 'upstream/master' into insertOverwrite
e76e85a [Yin Huai] Address comments.
ac31b3c [Yin Huai] Merge remote-tracking branch 'upstream/master' into insertOverwrite
f30bdad [Yin Huai] Use toDF.
99da57e [Yin Huai] Merge remote-tracking branch 'upstream/master' into insertOverwrite
6b7545c [Yin Huai] Add a pre write check to the data source API.
a88c516 [Yin Huai] DDLParser will take a parsering function to take care CTAS statements.
Lifts `HiveMetastoreCatalog.refreshTable` to `Catalog`. Adds `RefreshTable` command to refresh (possibly cached) metadata in external data sources tables.
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Author: Cheng Lian <lian@databricks.com>
Closes#4624 from liancheng/refresh-table and squashes the following commits:
8d1aa4c [Cheng Lian] Adds REFRESH TABLE command
Author: Michael Armbrust <michael@databricks.com>
Closes#4587 from marmbrus/position and squashes the following commits:
0810052 [Michael Armbrust] fix tests
395c019 [Michael Armbrust] Merge remote-tracking branch 'marmbrus/position' into position
e155dce [Michael Armbrust] more errors
f3efa51 [Michael Armbrust] Update AnalysisException.scala
d45ff60 [Michael Armbrust] [SQL] Initial support for reporting location of error in sql string
When profiling the Join / Aggregate queries via VisualVM, I noticed lots of `SpecificMutableRow` objects created, as well as the `MutableValue`, since the `SpecificMutableRow` are mostly used in data source implementation, but the `copy` method could be called multiple times in upper modules (e.g. in Join / aggregation etc.), duplicated instances created should be avoid.
Author: Cheng Hao <hao.cheng@intel.com>
Closes#4619 from chenghao-intel/specific_mutable_row and squashes the following commits:
9300d23 [Cheng Hao] update the SpecificMutableRow.copy
select k from (select key k, max(value) v from src group by k) t
Author: Daoyuan Wang <daoyuan.wang@intel.com>
Author: Michael Armbrust <michael@databricks.com>
Closes#4415 from adrian-wang/groupprune and squashes the following commits:
5d2d8a3 [Daoyuan Wang] address Michael's comments
61f8ef7 [Daoyuan Wang] add a unit test
80ddcc6 [Daoyuan Wang] keep project
b69d385 [Daoyuan Wang] add a prune rule for grouping set
This PR fix the issue SPARK-3365.
The reason is Spark generated wrong schema for the type `List` in `ScalaReflection.scala`
for example:
the generated schema for type `Seq[String]` is:
```
{"name":"x","type":{"type":"array","elementType":"string","containsNull":true},"nullable":true,"metadata":{}}`
```
the generated schema for type `List[String]` is:
```
{"name":"x","type":{"type":"struct","fields":[]},"nullable":true,"metadata":{}}`
```
Author: tianyi <tianyi.asiainfo@gmail.com>
Closes#4581 from tianyi/SPARK-3365 and squashes the following commits:
a097e86 [tianyi] change the order of resolution in ScalaReflection.scala
Author: Michael Armbrust <michael@databricks.com>
Author: wangfei <wangfei1@huawei.com>
Closes#4558 from marmbrus/errorMessages and squashes the following commits:
5e5ab50 [Michael Armbrust] Merge pull request #15 from scwf/errorMessages
fa38881 [wangfei] fix for grouping__id
f279a71 [wangfei] make right references for ScriptTransformation
d29fbde [Michael Armbrust] extra case
1a797b4 [Michael Armbrust] comments
d4e9015 [Michael Armbrust] add comment
af9e668 [Michael Armbrust] no braces
34eb3a4 [Michael Armbrust] more work
6197cd5 [Michael Armbrust] [SQL] Better error messages for analysis failures
As a follow-up to https://github.com/apache/spark/pull/4524
Author: Reynold Xin <rxin@databricks.com>
Closes#4539 from rxin/SPARK-3688 and squashes the following commits:
5ac56c7 [Reynold Xin] exists
da8eea4 [Reynold Xin] [SPARK-3688][SQL] More inline comments for LogicalPlan.
This PR fixed the resolving problem described in https://issues.apache.org/jira/browse/SPARK-3688
```
CREATE TABLE t1(x INT);
CREATE TABLE t2(a STRUCT<x: INT>, k INT);
SELECT a.x FROM t1 a JOIN t2 b ON a.x = b.k;
```
Author: tianyi <tianyi.asiainfo@gmail.com>
Closes#4524 from tianyi/SPARK-3688 and squashes the following commits:
237a256 [tianyi] resolve a name with table.column pattern first.
Also I fix a bunch of bad output in test cases.
Author: Michael Armbrust <michael@databricks.com>
Closes#4520 from marmbrus/selfJoin and squashes the following commits:
4f4a85c [Michael Armbrust] comments
49c8e26 [Michael Armbrust] fix tests
6fc38de [Michael Armbrust] fix style
55d64b3 [Michael Armbrust] fix dataframe selfjoins
Also start from the bottom so we show the first error instead of the top error.
Author: Michael Armbrust <michael@databricks.com>
Closes#4439 from marmbrus/analysisException and squashes the following commits:
45862a0 [Michael Armbrust] fix hive test
a773bba [Michael Armbrust] Merge remote-tracking branch 'origin/master' into analysisException
f88079f [Michael Armbrust] update more cases
fede90a [Michael Armbrust] newline
fbf4bc3 [Michael Armbrust] move to sql
6235db4 [Michael Armbrust] [SQL] Add an exception for analysis errors.
Author: Michael Armbrust <michael@databricks.com>
Closes#4436 from marmbrus/dfToString and squashes the following commits:
8a3c35f [Michael Armbrust] Merge remote-tracking branch 'origin/master' into dfToString
b72a81b [Michael Armbrust] add toString
~~The rule is simple: If you want `a.b` work, then `a` must be some level of nested array of struct(level 0 means just a StructType). And the result of `a.b` is same level of nested array of b-type.
An optimization is: the resolve chain looks like `Attribute -> GetItem -> GetField -> GetField ...`, so we could transmit the nested array information between `GetItem` and `GetField` to avoid repeated computation of `innerDataType` and `containsNullList` of that nested array.~~
marmbrus Could you take a look?
to evaluate `a.b`, if `a` is array of struct, then `a.b` means get field `b` on each element of `a`, and return a result of array.
Author: Wenchen Fan <cloud0fan@outlook.com>
Closes#2405 from cloud-fan/nested-array-dot and squashes the following commits:
08a228a [Wenchen Fan] support dot notation on array of struct
Now in Catalyst's rules, predicates can not be pushed through "Generate" nodes. Further more, partition pruning in HiveTableScan can not be applied on those queries involves "Generate". This makes such queries very inefficient. In practice, it finds patterns like
```scala
Filter(predicate, Generate(generator, _, _, _, grandChild))
```
and splits the predicate into 2 parts by referencing the generated column from Generate node or not. And a new Filter will be created for those conjuncts can be pushed beneath Generate node. If nothing left for the original Filter, it will be removed.
For example, physical plan for query
```sql
select len, bk
from s_server lateral view explode(len_arr) len_table as len
where len > 5 and day = '20150102';
```
where 'day' is a partition column in metastore is like this in current version of Spark SQL:
> Project [len, bk]
>
> Filter ((len > "5") && "(day = "20150102")")
>
> Generate explode(len_arr), true, false
>
> HiveTableScan [bk, len_arr, day], (MetastoreRelation default, s_server, None), None
But theoretically the plan should be like this
> Project [len, bk]
>
> Filter (len > "5")
>
> Generate explode(len_arr), true, false
>
> HiveTableScan [bk, len_arr, day], (MetastoreRelation default, s_server, None), Some(day = "20150102")
Where partition pruning predicates can be pushed to HiveTableScan nodes.
Author: Lu Yan <luyan02@baidu.com>
Closes#4394 from ianluyan/ppd and squashes the following commits:
a67dce9 [Lu Yan] Fix English grammar.
7cea911 [Lu Yan] Revised based on @marmbrus's opinions
ffc59fc [Lu Yan] [SPARK-5614][SQL] Predicate pushdown through Generate.
Otherwise, the following will always return false in Java.
```scala
dataType instanceof StringType
```
Author: Reynold Xin <rxin@databricks.com>
Closes#4463 from rxin/type-companion-object and squashes the following commits:
04d5d8d [Reynold Xin] Comment.
976e11e [Reynold Xin] [SPARK-5675][SQL]StringType case object should be subclass of StringType class
An example:
```
year month AVG('Adj Close) MAX('Adj Close)
1980 12 0.503218 0.595103
1981 01 0.523289 0.570307
1982 02 0.436504 0.475256
1983 03 0.410516 0.442194
1984 04 0.450090 0.483521
```
Author: Reynold Xin <rxin@databricks.com>
Closes#4416 from rxin/SPARK-5643 and squashes the following commits:
d0e0d6e [Reynold Xin] [SQL] Minor update to data source and statistics documentation.
269da83 [Reynold Xin] Updated isLocal comment.
2cf3c27 [Reynold Xin] Moved logic into optimizer.
1a04d8b [Reynold Xin] [SPARK-5643][SQL] Add a show method to print the content of a DataFrame in columnar format.
When the `GetField` chain(`a.b.c.d.....`) is interrupted by `GetItem` like `a.b[0].c.d....`, then the check of ambiguous reference to fields is broken.
The reason is that: for something like `a.b[0].c.d`, we first parse it to `GetField(GetField(GetItem(Unresolved("a.b"), 0), "c"), "d")`. Then in `LogicalPlan#resolve`, we resolve `"a.b"` and build a `GetField` chain from bottom(the relation). But for the 2 outer `GetFiled`, we have to resolve them in `Analyzer` or do it in `GetField` lazily, check data type of child, search needed field, etc. which is similar to what we have done in `LogicalPlan#resolve`.
So in this PR, the fix is just copy the same logic in `LogicalPlan#resolve` to `Analyzer`, which is simple and quick, but I do suggest introduce `UnresolvedGetFiled` like I explained in https://github.com/apache/spark/pull/2405.
Author: Wenchen Fan <cloud0fan@outlook.com>
Closes#4068 from cloud-fan/simple and squashes the following commits:
a6857b5 [Wenchen Fan] fix import order
8411c40 [Wenchen Fan] use UnresolvedGetField