README updates for PXF build/setup instructions (#3135)

* README updates for PXF setup instructions

* PXF README updates for PXF setup instructions

* test update

* README updates for PXF setup instructions

* PXF README updates for PXF setup instructions

* note on curl depedancy

* minor update

README.macOS.bash

@@ -16,7 +16,7 @@ brew install apr # gpperfmon
 brew install apr-util # gpperfmon
 brew link --force apr
 brew link --force apr-util
-
+brew install json-c # pxf
 
 # Installing Golang
 mkdir -p ~/go/src

README.md

@@ -194,6 +194,14 @@ to be available in the environment. [Build and Install](#buildOrca) the latest O
 
 If you want to build GPDB without ORCA, configure requires `--disable-orca` flag to be set.
 
+### Building GPDB with PXF
+PXF is an extension framework for GPDB to enable access to external hadoop datasets.
+Refer to [PXF extension](https://github.com/greenplum-db/gpdb/tree/master/gpAux/extensions/pxf) for more information.
+Currently, GPDPB is built with PXF by default. If you don't need PXF, use --disable-pxf flag with configure.
+Also PXF requires curl version > 7.21.3. On most centos6 environments with curl version 7.19 compilation will fail due to this dependancy.
+You can either try upgrading your curl version, or simply disable pxf during build.
+
+
 ```
 # Clean environment
 make distclean

gpAux/extensions/pxf/README.md

-# The PXF extension client for GPDB
+# The PXF extension for GPDB
 
-PXF is an extensible framework that allows GPDB or any other parallel database to query external datasets. The framework is built in Java and provides built-in connectors for accessing data of various formats(text,sequence files, orc,etc) that exists inside HDFS files, Hive tables, HBase tables and many more stores.
-This module includes the PXF C client and using the 'pxf' protocol with external table, GPDB can query external datasets via PXF service that runs alongside GPDB segments.
+PXF is an extension framework that allows GPDB or any other database to query external distributed datasets. The framework is built in Java and provides built-in connectors for accessing data of various formats(text,sequence files, avro, orc,etc) that may exist inside HDFS files, Hive tables, HBase tables and many more stores.
+PXF consists of a server side JVM based component and a C client component which serves as the means for GPDB to interact with the PXF service.
+This module only includes the PXF C client and the build instructions only builds the client.
+Using the 'pxf' protocol with external table, GPDB can query external datasets via PXF service that runs alongside GPDB segments.
 
 ## Table of Contents
 
@@ -66,13 +68,9 @@ LOCATION ('pxf://localhost:51200/tmp/dummy1' \
 FORMAT 'TEXT' (DELIMITER ',');
 ```
 
-If you wish to use PXF with Hadoop, instructions will be made available shortly.
-
-
-
 
 Please refer to [PXF Setup](https://cwiki.apache.org/confluence/display/HAWQ/PXF+Build+and+Install) for instructions to setup PXF.
-Once you also install and run PXF server on the machines where GPDB segments are run, you can select data from the demo PXF profile:
+Once you install and run PXF server alongside the GPDB segments, you can select data from the demo PXF profile:
 ```
 # SELECT * from pxf_read_test order by a;
 
@@ -88,6 +86,10 @@ Once you also install and run PXF server on the machines where GPDB segments are
 ```
 
 
+If you wish to use PXF with Hadoop, you will need to integrate with Hdfs or Hive, you can refer to the above doc on steps to install them.
+
+
+
 ## Run regression tests
 
 ```