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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2021/04/02 13:11:15 UTC
[GitHub] [spark] srowen commented on a change in pull request #31010: [SPARK-33976][SQL] Spark script TRANSFORM related change doc
srowen commented on a change in pull request #31010:
URL: https://github.com/apache/spark/pull/31010#discussion_r606228807
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
Review comment:
Maybe tick-quote map_script, reduce_script
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
Review comment:
hive -> Hive
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
+differentiate NULL values from empty strings. The standard output of the user script will be treated as
+TAB-separated STRING columns, any cell containing only \N will be re-interpreted as a NULL, and then the
+resulting STRING column will be cast to the data type specified in the table declaration in the usual way.
+User scripts can output debug information to standard error which will be shown on the task detail page on hadoop.
+These defaults can be overridden with `ROW FORMAT DELIMITED`.
+
+### Syntax
+
+```sql
+rowFormat
+ : ROW FORMAT SERDE serde_class [ WITH SERDEPROPERTIES serde_props ]
+ | ROW FORMAT DELIMITED
+ [ FIELDS TERMINATED BY fields_terminated_char [ ESCAPED BY escapedBy ] ]
+ [ COLLECTION ITEMS TERMINATED BY collectionItemsTerminatedBy ]
+ [ MAP KEYS TERMINATED BY keysTerminatedBy ]
+ [ LINES TERMINATED BY linesSeparatedBy ]
+ [ NULL DEFINED AS nullDefinedAs ]
+
+inRowFormat=rowFormat
+outRowFormat=rowFormat
+namedExpressionSeq = named_expression [ , ... ]
+
+transformClause:
+ SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]
+ [ inRowFormat ]
+ [ RECORDWRITER recordWriter_class ]
+ USING script
+ [ AS ( [ col_name [ col_type ]] [ , ... ] ) ]
+ [ outRowFormat ]
+ [ RECORDREADER recordReader_class ]
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ... ] ]
+ [ HAVING boolean_expression ]
+```
+
+### Parameters
+
+* **named_expression**
+
+ An expression with an assigned name. In general, it denotes a column expression.
+
+ **Syntax:** `expression [AS] [alias]`
+
+* **row_format**
+
+ Use the `SERDE` clause to specify a custom SerDe for one table. Otherwise, use the `DELIMITED` clause to use the native SerDe and specify the delimiter, escape character, null character and so on.
+
+* **SERDE**
+
+ Specifies a custom SerDe for one table.
+
+* **serde_class**
+
+ Specifies a fully-qualified class name of a custom SerDe.
+
+* **SERDEPROPERTIES**
+
+ A list of key-value pairs that is used to tag the SerDe definition.
+
+* **DELIMITED**
+
+ The `DELIMITED` clause can be used to specify the native SerDe and state the delimiter, escape character, null character and so on.
+
+* **FIELDS TERMINATED BY**
+
+ Used to define a column separator.
+
+* **COLLECTION ITEMS TERMINATED BY**
+
+ Used to define a collection item separator.
+
+* **MAP KEYS TERMINATED BY**
+
+ Used to define a map key separator.
+
+* **LINES TERMINATED BY**
+
+ Used to define a row separator.
+
+* **NULL DEFINED AS**
+
+ Used to define the specific value for NULL.
+
+* **ESCAPED BY**
+
+ Used for escape mechanism.
+
+* **RECORDREADER**
+
+ Specifies a custom RecordReader for one table.
+
+* **RECORDWRITER**
+
+ Specifies a custom RecordWriter for one table.
+
+* **recordReader_class**
+
+ Specifies a fully-qualified class name of a custom RecordReader.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordReader`
+
+* **recordWriter_class**
+
+ Specifies a fully-qualified class name of a custom RecordWriter.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordWriter`.
+
+* **script**
+
+ Specify a command to process data.
+
+* **boolean_expression**
+
+ Specifies any expression that evaluates to a result type `boolean`. Two or
+ more expressions may be combined together using the logical
+ operators ( `AND`, `OR` ).
+
+* **expression**
+
+ Specifies combination of one or more values, operators and SQL functions that results in a value.
+
+### Without Hive support Mode
+
+Now Spark Script transform can run without `-Phive` or `SparkSession.builder.enableHiveSupport()`.
+In this case, now we only use script transform with `ROW FORMAT DELIMIT` and treat all value passed
+to script as string.
+
+### With Hive Support Mode
+
+When build Spark with `-Phive` and start Spark SQL with `enableHiveSupport()`, we can use script
+transform with Hive SerDe and both `ROW FORMAT DELIMIT`.
+
+### Schema-less Script Transforms
+
+If there don't have AS clause after USING my_script, Spark assumes that the output of the script contains 2 parts:
+
+ 1. key: which is before the first tab,
+ 2. value: which is the rest after the first tab.
+
+Note that this is different from specifying AS key, value because in that case, value will only contain the portion
Review comment:
AS -> an AS
"key, value"
Maybe tick-quote all these reserved words too, like NULL as well?
value -> the value
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
+differentiate NULL values from empty strings. The standard output of the user script will be treated as
+TAB-separated STRING columns, any cell containing only \N will be re-interpreted as a NULL, and then the
+resulting STRING column will be cast to the data type specified in the table declaration in the usual way.
+User scripts can output debug information to standard error which will be shown on the task detail page on hadoop.
+These defaults can be overridden with `ROW FORMAT DELIMITED`.
+
+### Syntax
+
+```sql
+rowFormat
+ : ROW FORMAT SERDE serde_class [ WITH SERDEPROPERTIES serde_props ]
+ | ROW FORMAT DELIMITED
+ [ FIELDS TERMINATED BY fields_terminated_char [ ESCAPED BY escapedBy ] ]
+ [ COLLECTION ITEMS TERMINATED BY collectionItemsTerminatedBy ]
+ [ MAP KEYS TERMINATED BY keysTerminatedBy ]
+ [ LINES TERMINATED BY linesSeparatedBy ]
+ [ NULL DEFINED AS nullDefinedAs ]
+
+inRowFormat=rowFormat
+outRowFormat=rowFormat
+namedExpressionSeq = named_expression [ , ... ]
+
+transformClause:
+ SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]
+ [ inRowFormat ]
+ [ RECORDWRITER recordWriter_class ]
+ USING script
+ [ AS ( [ col_name [ col_type ]] [ , ... ] ) ]
+ [ outRowFormat ]
+ [ RECORDREADER recordReader_class ]
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ... ] ]
+ [ HAVING boolean_expression ]
+```
+
+### Parameters
+
+* **named_expression**
+
+ An expression with an assigned name. In general, it denotes a column expression.
+
+ **Syntax:** `expression [AS] [alias]`
+
+* **row_format**
+
+ Use the `SERDE` clause to specify a custom SerDe for one table. Otherwise, use the `DELIMITED` clause to use the native SerDe and specify the delimiter, escape character, null character and so on.
+
+* **SERDE**
+
+ Specifies a custom SerDe for one table.
+
+* **serde_class**
+
+ Specifies a fully-qualified class name of a custom SerDe.
+
+* **SERDEPROPERTIES**
+
+ A list of key-value pairs that is used to tag the SerDe definition.
+
+* **DELIMITED**
+
+ The `DELIMITED` clause can be used to specify the native SerDe and state the delimiter, escape character, null character and so on.
+
+* **FIELDS TERMINATED BY**
+
+ Used to define a column separator.
+
+* **COLLECTION ITEMS TERMINATED BY**
+
+ Used to define a collection item separator.
+
+* **MAP KEYS TERMINATED BY**
+
+ Used to define a map key separator.
+
+* **LINES TERMINATED BY**
+
+ Used to define a row separator.
+
+* **NULL DEFINED AS**
+
+ Used to define the specific value for NULL.
+
+* **ESCAPED BY**
+
+ Used for escape mechanism.
+
+* **RECORDREADER**
+
+ Specifies a custom RecordReader for one table.
+
+* **RECORDWRITER**
+
+ Specifies a custom RecordWriter for one table.
+
+* **recordReader_class**
+
+ Specifies a fully-qualified class name of a custom RecordReader.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordReader`
+
+* **recordWriter_class**
+
+ Specifies a fully-qualified class name of a custom RecordWriter.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordWriter`.
+
+* **script**
+
+ Specify a command to process data.
+
+* **boolean_expression**
+
+ Specifies any expression that evaluates to a result type `boolean`. Two or
+ more expressions may be combined together using the logical
+ operators ( `AND`, `OR` ).
+
+* **expression**
+
+ Specifies combination of one or more values, operators and SQL functions that results in a value.
+
+### Without Hive support Mode
+
+Now Spark Script transform can run without `-Phive` or `SparkSession.builder.enableHiveSupport()`.
+In this case, now we only use script transform with `ROW FORMAT DELIMIT` and treat all value passed
+to script as string.
+
+### With Hive Support Mode
+
+When build Spark with `-Phive` and start Spark SQL with `enableHiveSupport()`, we can use script
Review comment:
build -> built
start -> started
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
Review comment:
What is 'format' here?
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
+differentiate NULL values from empty strings. The standard output of the user script will be treated as
+TAB-separated STRING columns, any cell containing only \N will be re-interpreted as a NULL, and then the
+resulting STRING column will be cast to the data type specified in the table declaration in the usual way.
+User scripts can output debug information to standard error which will be shown on the task detail page on hadoop.
+These defaults can be overridden with `ROW FORMAT DELIMITED`.
+
+### Syntax
+
+```sql
+rowFormat
+ : ROW FORMAT SERDE serde_class [ WITH SERDEPROPERTIES serde_props ]
+ | ROW FORMAT DELIMITED
+ [ FIELDS TERMINATED BY fields_terminated_char [ ESCAPED BY escapedBy ] ]
+ [ COLLECTION ITEMS TERMINATED BY collectionItemsTerminatedBy ]
+ [ MAP KEYS TERMINATED BY keysTerminatedBy ]
+ [ LINES TERMINATED BY linesSeparatedBy ]
+ [ NULL DEFINED AS nullDefinedAs ]
+
+inRowFormat=rowFormat
+outRowFormat=rowFormat
+namedExpressionSeq = named_expression [ , ... ]
+
+transformClause:
+ SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]
+ [ inRowFormat ]
+ [ RECORDWRITER recordWriter_class ]
+ USING script
+ [ AS ( [ col_name [ col_type ]] [ , ... ] ) ]
+ [ outRowFormat ]
+ [ RECORDREADER recordReader_class ]
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ... ] ]
+ [ HAVING boolean_expression ]
+```
+
+### Parameters
+
+* **named_expression**
+
+ An expression with an assigned name. In general, it denotes a column expression.
+
+ **Syntax:** `expression [AS] [alias]`
+
+* **row_format**
+
+ Use the `SERDE` clause to specify a custom SerDe for one table. Otherwise, use the `DELIMITED` clause to use the native SerDe and specify the delimiter, escape character, null character and so on.
+
+* **SERDE**
+
+ Specifies a custom SerDe for one table.
+
+* **serde_class**
+
+ Specifies a fully-qualified class name of a custom SerDe.
+
+* **SERDEPROPERTIES**
+
+ A list of key-value pairs that is used to tag the SerDe definition.
+
+* **DELIMITED**
+
+ The `DELIMITED` clause can be used to specify the native SerDe and state the delimiter, escape character, null character and so on.
+
+* **FIELDS TERMINATED BY**
+
+ Used to define a column separator.
+
+* **COLLECTION ITEMS TERMINATED BY**
+
+ Used to define a collection item separator.
+
+* **MAP KEYS TERMINATED BY**
+
+ Used to define a map key separator.
+
+* **LINES TERMINATED BY**
+
+ Used to define a row separator.
+
+* **NULL DEFINED AS**
+
+ Used to define the specific value for NULL.
+
+* **ESCAPED BY**
+
+ Used for escape mechanism.
+
+* **RECORDREADER**
+
+ Specifies a custom RecordReader for one table.
+
+* **RECORDWRITER**
+
+ Specifies a custom RecordWriter for one table.
+
+* **recordReader_class**
+
+ Specifies a fully-qualified class name of a custom RecordReader.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordReader`
+
+* **recordWriter_class**
+
+ Specifies a fully-qualified class name of a custom RecordWriter.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordWriter`.
+
+* **script**
+
+ Specify a command to process data.
+
+* **boolean_expression**
+
+ Specifies any expression that evaluates to a result type `boolean`. Two or
+ more expressions may be combined together using the logical
+ operators ( `AND`, `OR` ).
+
+* **expression**
+
+ Specifies combination of one or more values, operators and SQL functions that results in a value.
+
+### Without Hive support Mode
+
+Now Spark Script transform can run without `-Phive` or `SparkSession.builder.enableHiveSupport()`.
+In this case, now we only use script transform with `ROW FORMAT DELIMIT` and treat all value passed
+to script as string.
+
+### With Hive Support Mode
+
+When build Spark with `-Phive` and start Spark SQL with `enableHiveSupport()`, we can use script
+transform with Hive SerDe and both `ROW FORMAT DELIMIT`.
+
+### Schema-less Script Transforms
+
+If there don't have AS clause after USING my_script, Spark assumes that the output of the script contains 2 parts:
Review comment:
If there is no AS clause ...
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
+differentiate NULL values from empty strings. The standard output of the user script will be treated as
+TAB-separated STRING columns, any cell containing only \N will be re-interpreted as a NULL, and then the
+resulting STRING column will be cast to the data type specified in the table declaration in the usual way.
+User scripts can output debug information to standard error which will be shown on the task detail page on hadoop.
+These defaults can be overridden with `ROW FORMAT DELIMITED`.
+
+### Syntax
+
+```sql
+rowFormat
+ : ROW FORMAT SERDE serde_class [ WITH SERDEPROPERTIES serde_props ]
+ | ROW FORMAT DELIMITED
+ [ FIELDS TERMINATED BY fields_terminated_char [ ESCAPED BY escapedBy ] ]
+ [ COLLECTION ITEMS TERMINATED BY collectionItemsTerminatedBy ]
+ [ MAP KEYS TERMINATED BY keysTerminatedBy ]
+ [ LINES TERMINATED BY linesSeparatedBy ]
+ [ NULL DEFINED AS nullDefinedAs ]
+
+inRowFormat=rowFormat
+outRowFormat=rowFormat
+namedExpressionSeq = named_expression [ , ... ]
+
+transformClause:
+ SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]
+ [ inRowFormat ]
+ [ RECORDWRITER recordWriter_class ]
+ USING script
+ [ AS ( [ col_name [ col_type ]] [ , ... ] ) ]
+ [ outRowFormat ]
+ [ RECORDREADER recordReader_class ]
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ... ] ]
+ [ HAVING boolean_expression ]
+```
+
+### Parameters
+
+* **named_expression**
+
+ An expression with an assigned name. In general, it denotes a column expression.
+
+ **Syntax:** `expression [AS] [alias]`
+
+* **row_format**
+
+ Use the `SERDE` clause to specify a custom SerDe for one table. Otherwise, use the `DELIMITED` clause to use the native SerDe and specify the delimiter, escape character, null character and so on.
+
+* **SERDE**
+
+ Specifies a custom SerDe for one table.
+
+* **serde_class**
+
+ Specifies a fully-qualified class name of a custom SerDe.
+
+* **SERDEPROPERTIES**
+
+ A list of key-value pairs that is used to tag the SerDe definition.
+
+* **DELIMITED**
+
+ The `DELIMITED` clause can be used to specify the native SerDe and state the delimiter, escape character, null character and so on.
+
+* **FIELDS TERMINATED BY**
+
+ Used to define a column separator.
+
+* **COLLECTION ITEMS TERMINATED BY**
+
+ Used to define a collection item separator.
+
+* **MAP KEYS TERMINATED BY**
+
+ Used to define a map key separator.
+
+* **LINES TERMINATED BY**
+
+ Used to define a row separator.
+
+* **NULL DEFINED AS**
+
+ Used to define the specific value for NULL.
+
+* **ESCAPED BY**
+
+ Used for escape mechanism.
+
+* **RECORDREADER**
+
+ Specifies a custom RecordReader for one table.
+
+* **RECORDWRITER**
+
+ Specifies a custom RecordWriter for one table.
+
+* **recordReader_class**
+
+ Specifies a fully-qualified class name of a custom RecordReader.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordReader`
+
+* **recordWriter_class**
+
+ Specifies a fully-qualified class name of a custom RecordWriter.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordWriter`.
+
+* **script**
+
+ Specify a command to process data.
+
+* **boolean_expression**
+
+ Specifies any expression that evaluates to a result type `boolean`. Two or
+ more expressions may be combined together using the logical
+ operators ( `AND`, `OR` ).
+
+* **expression**
+
+ Specifies combination of one or more values, operators and SQL functions that results in a value.
+
+### Without Hive support Mode
+
+Now Spark Script transform can run without `-Phive` or `SparkSession.builder.enableHiveSupport()`.
+In this case, now we only use script transform with `ROW FORMAT DELIMIT` and treat all value passed
+to script as string.
Review comment:
string -> a string
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
Review comment:
Quote \N - what ASCII value is it, for reference? 0?
##########
File path: docs/sql-ref-syntax-qry-select.md
##########
@@ -164,6 +164,11 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { [ named_expression | regex_column_na
)
```
+* **TRANSFORM**
+
+ Specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE) query specification to transform
Review comment:
hive -> Hive
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
+to the user script, Similarly, all NULL values will be converted to the literal string \N in order to
+differentiate NULL values from empty strings. The standard output of the user script will be treated as
+TAB-separated STRING columns, any cell containing only \N will be re-interpreted as a NULL, and then the
+resulting STRING column will be cast to the data type specified in the table declaration in the usual way.
+User scripts can output debug information to standard error which will be shown on the task detail page on hadoop.
+These defaults can be overridden with `ROW FORMAT DELIMITED`.
+
+### Syntax
+
+```sql
+rowFormat
+ : ROW FORMAT SERDE serde_class [ WITH SERDEPROPERTIES serde_props ]
+ | ROW FORMAT DELIMITED
+ [ FIELDS TERMINATED BY fields_terminated_char [ ESCAPED BY escapedBy ] ]
+ [ COLLECTION ITEMS TERMINATED BY collectionItemsTerminatedBy ]
+ [ MAP KEYS TERMINATED BY keysTerminatedBy ]
+ [ LINES TERMINATED BY linesSeparatedBy ]
+ [ NULL DEFINED AS nullDefinedAs ]
+
+inRowFormat=rowFormat
+outRowFormat=rowFormat
+namedExpressionSeq = named_expression [ , ... ]
+
+transformClause:
+ SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]
+ [ inRowFormat ]
+ [ RECORDWRITER recordWriter_class ]
+ USING script
+ [ AS ( [ col_name [ col_type ]] [ , ... ] ) ]
+ [ outRowFormat ]
+ [ RECORDREADER recordReader_class ]
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ... ] ]
+ [ HAVING boolean_expression ]
+```
+
+### Parameters
+
+* **named_expression**
+
+ An expression with an assigned name. In general, it denotes a column expression.
+
+ **Syntax:** `expression [AS] [alias]`
+
+* **row_format**
+
+ Use the `SERDE` clause to specify a custom SerDe for one table. Otherwise, use the `DELIMITED` clause to use the native SerDe and specify the delimiter, escape character, null character and so on.
+
+* **SERDE**
+
+ Specifies a custom SerDe for one table.
+
+* **serde_class**
+
+ Specifies a fully-qualified class name of a custom SerDe.
+
+* **SERDEPROPERTIES**
+
+ A list of key-value pairs that is used to tag the SerDe definition.
+
+* **DELIMITED**
+
+ The `DELIMITED` clause can be used to specify the native SerDe and state the delimiter, escape character, null character and so on.
+
+* **FIELDS TERMINATED BY**
+
+ Used to define a column separator.
+
+* **COLLECTION ITEMS TERMINATED BY**
+
+ Used to define a collection item separator.
+
+* **MAP KEYS TERMINATED BY**
+
+ Used to define a map key separator.
+
+* **LINES TERMINATED BY**
+
+ Used to define a row separator.
+
+* **NULL DEFINED AS**
+
+ Used to define the specific value for NULL.
+
+* **ESCAPED BY**
+
+ Used for escape mechanism.
+
+* **RECORDREADER**
+
+ Specifies a custom RecordReader for one table.
+
+* **RECORDWRITER**
+
+ Specifies a custom RecordWriter for one table.
+
+* **recordReader_class**
+
+ Specifies a fully-qualified class name of a custom RecordReader.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordReader`
+
+* **recordWriter_class**
+
+ Specifies a fully-qualified class name of a custom RecordWriter.
+ Default value is `org.apache.hadoop.hive.ql.exec.TextRecordWriter`.
+
+* **script**
+
+ Specify a command to process data.
+
+* **boolean_expression**
+
+ Specifies any expression that evaluates to a result type `boolean`. Two or
+ more expressions may be combined together using the logical
+ operators ( `AND`, `OR` ).
+
+* **expression**
+
+ Specifies combination of one or more values, operators and SQL functions that results in a value.
+
+### Without Hive support Mode
+
+Now Spark Script transform can run without `-Phive` or `SparkSession.builder.enableHiveSupport()`.
Review comment:
Remove 'now' in these sentences?
we -> Spark in many cases - we don't run it, Spark does
Script -> script?
##########
File path: docs/sql-ref-syntax-qry-select-transform.md
##########
@@ -0,0 +1,297 @@
+---
+layout: global
+title: TRANSFORM
+displayTitle: TRANSFORM
+license: |
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+---
+
+### Description
+
+The `TRANSFORM` clause is used to specifies a hive-style transform (SELECT TRANSFORM/MAP/REDUCE)
+query specification to transform the input by forking and running the specified script. Users can
+plug in their own custom mappers and reducers in the data stream by using features natively supported
+in the Spark/Hive language. e.g. in order to run a custom mapper script - map_script - and a custom
+reducer script - reduce_script - the user can issue the following command which uses the TRANSFORM
+clause to embed the mapper and the reducer scripts.
+
+Currently, Spark's script transform support two mode:
+
+ 1. Without Hive: It means we run Spark SQL without hive support, in this mode, we can use default format
+ by treating data as STRING and use Spark's own SerDe.
+ 2. WIth Hive: It means we run Spark SQL with Hive support, in this mode, when we use default format,
+ it will be treated as Hive default fomat. And we can use Hive supported SerDe to process data.
+
+In both mode with default format, columns will be transformed to STRING and delimited by TAB before feeding
Review comment:
mode -> modes
TAB -> tabs
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