maropu commented on a change in pull request #31010: URL: https://github.com/apache/spark/pull/31010#discussion_r608261037
########## File path: docs/sql-ref-syntax-qry-select-transform.md ########## @@ -0,0 +1,263 @@ +--- +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 running a specified script. Users can +plug in their own custom mappers and reducers in the data stream by using features natively supported +in the Spark SQL. 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. + +In default format, columns will be transformed to `STRING` and delimited by tabs 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 +SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ] + [ inRowFormat ] + [ RECORDWRITER recordWriter_class ] + USING script [ AS ( [ col_name [ col_type ]] [ , ... ] ) ] + [ outRowFormat ] + [ RECORDREADER recordReader_class ] + FROM { from_item [ , ... ] } Review comment: I think we don't need `FROM` here because this is described in the doc of `SELECT`: https://spark.apache.org/docs/latest/sql-ref-syntax-qry-select.html ########## File path: docs/sql-ref-syntax-qry-select-transform.md ########## @@ -0,0 +1,263 @@ +--- +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 running a specified script. Users can +plug in their own custom mappers and reducers in the data stream by using features natively supported +in the Spark SQL. 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. + +In default format, columns will be transformed to `STRING` and delimited by tabs 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 +SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ] + [ inRowFormat ] + [ RECORDWRITER recordWriter_class ] + USING script [ AS ( [ col_name [ col_type ]] [ , ... ] ) ] + [ outRowFormat ] + [ RECORDREADER recordReader_class ] + FROM { from_item [ , ... ] } + +rowFormat Review comment: This syntax is ANTLR one, so please follow how to write a syntax? e.g., https://github.com/apache/spark/blame/master/docs/sql-ref-syntax-qry-select-groupby.md#L37-L39 ########## File path: docs/sql-ref-syntax-qry-select-transform.md ########## @@ -0,0 +1,263 @@ +--- +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 running a specified script. Users can +plug in their own custom mappers and reducers in the data stream by using features natively supported +in the Spark SQL. 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. + +In default format, columns will be transformed to `STRING` and delimited by tabs 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`. Review comment: Could you make a subsection for the SERDE behaviour and move the descriptions there? For example ``` ### Parameters ... ### <A title> <Descriptions to describe the SERDE behaviour> ### Schema-less Script Transforms ... ``` ########## File path: docs/sql-ref-syntax-qry-select-transform.md ########## @@ -0,0 +1,263 @@ +--- +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 running a specified script. Users can +plug in their own custom mappers and reducers in the data stream by using features natively supported +in the Spark SQL. 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. + +In default format, columns will be transformed to `STRING` and delimited by tabs 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 +SELECT [ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ] Review comment: `[ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq ]` -> `{ TRANSFORM ( namedExpressionSeq ) | MAP namedExpressionSeq | REDUCE namedExpressionSeq }` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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