JOIN in Apache Pig - json

Question

I have two files consisting of json objects in two different locations on my hdfs and I need to join those two depending on a common field.
First file consists of tweet data and has 34 fields (I literally counted). It looks like:
{"contributors": null, "truncated": false, "text": "US Bank Loans And credit card capitol one business", "avl_brand_all": ["US Bank"], "is_quote_status": false , "in_reply_to_status_id": null, "id": 770150015968825344, "favorite_count": 0, "avl_num_sentences": 1, "source": "<a href=\"http://twitter.com\" rel=\"nofollow\">Twitter Web Client</ a>", "retweeted": false, "coordinates": null, "entities": {"symbols": [], "user_mentions": [], "hashtags": [], "urls": [{"url": "<link>": [51, 74], "expand ed_url": "http://usbanklogins.com/bank/", "display_url": "usbanklogins.com/bank/"}]}, "in_reply_to_screen_name": null, "in_reply_to_user_id": null, "avl_word_tags": [{"distance": 1, " word": "u", "pos": "OTHER"}, {"distance": 1, "word": "bank", "pos": "NOUN"}, {"distance": 1, "word": "loan", "pos": "NOUN"}, {"distance": 1, "word": "credit", "pos": "NOUN"}, {"distan ce": 1, "word": "card", "pos": "NOUN"}, {"distance": 1, "word": "capitol", "pos": "VERB"}, {"distance": 1, "word": "one", "pos": "OTHER"}, {"distance": 1, "word": "business", "pos": " NOUN"}], "avl_brand_1": "US Bank", "retweet_count": 0, "avl_lexicon_text": "us bank loans and credit card capitol one business", "id_str": "770150015968825344", "favorited": false, "a vl_sentences": ["us bank loans and credit card capitol one business"], "user": {"follow_request_sent": false, "has_extended_profile": false, "profile_use_background_image": true, "id" : 485610502, "verified": false, "profile_text_color": "0C3E53", "profile_image_url_https": "<link>", "profile _sidebar_fill_color": "FFF7CC", "geo_enabled": false, "entities": {"url": {"urls": [{"url": "link", "indices": [0, 22], "expanded_url": "http://www.seowithme.com", " display_url": "seowithme.com"}]}, "description": {"urls": []}}, "followers_count": 347, "profile_sidebar_border_color": "F2E195", "location": "", "default_profile_image": false, "id_s tr": "485610502", "is_translation_enabled": false, "utc_offset": null, "statuses_count": 117, "description": "seowithme", "friends_count": 959, "profile_link_color": "FF0000", "profil e_image_url": "http://pbs.twimg.com/profile_images/2334489262/qyznw08zjrgv3vlxtdvt_normal.jpeg", "notifications": false, "profile_background_image_url_https": "https://abs.twimg.com/i mages/themes/theme12/bg.gif", "profile_background_color": "BADFCD", "profile_background_image_url": "http://abs.twimg.com/images/themes/theme12/bg.gif", "screen_name": "sajanshrestha2 2", "lang": "en", "following": false, "profile_background_tile": false, "favourites_count": 2, "name": "sajan shrestha", "url": "<link>", "created_at": "Tue Feb 07 11: 40:39 +0000 2012", "contributors_enabled": false, "time_zone": null, "protected": false, "default_profile": false, "is_translator": false, "listed_count": 0}, "avl_num_paragraphs": 1, "geo": null, "in_reply_to_user_id_str": null, "possibly_sensitive": false, "lang": "en", "created_at": "Mon Aug 29 06:44:07 +0000 2016", "avl_source": "individual", "in_reply_to_stat us_id_str": null, "place": null, "metadata": {"iso_language_code": "en", "result_type": "recent"}, "avl_num_words": 8}
The second file has json objects each having only two fields. Looks like:
{"avl_syntaxnet_tags": [{"pos_tag": "PRP", "position": "1", "dep_rel": "dep", "parent": "3", "word": "us"}, {"pos_tag": "NN", "position": "2", "dep_rel": "nn", "parent": "3", "word": "bank"}, {"pos_tag": "NNS", "position": "3", "dep_rel": "nsubj", "parent": "7", "word": "loans"}, {"pos_tag": "CC", "position": "4", "dep_rel": "cc", "parent": "3", "word": "and"}, {" pos_tag": "NN", "position": "5", "dep_rel": "nn", "parent": "6", "word": "credit"}, {"pos_tag": "NN", "position": "6", "dep_rel": "conj", "parent": "3", "word": "card"}, {"pos_tag": " VBP", "position": "7", "dep_rel": "ROOT", "parent": "0", "word": "capitol"}, {"pos_tag": "CD", "position": "8", "dep_rel": "num", "parent": "9", "word": "one"}, {"pos_tag": "NN", "pos ition": "9", "dep_rel": "dobj", "parent": "7", "word": "business"}], "avl_lexicon_text": "us bank loans and credit card capitol one business"}
Now, there is a common fiels in both the json_objects named avl_lexicon_text and I want to join these two objects using the common field.
I wrote the following Pig script for the join:
a = LOAD file1 as (a1, a2);
b = LOAD file2 as (b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16, b17, b18, b19, b20, b21, b22, b23, b24, b25, b26, b27, b28, b29, b30, b31, b32, b33, b34);
x = JOIN b BY b19 FULL, a BY a2;
STORE x INTO '$SYNTAXNET_OUTPUT';
I checked b19 is the avl_lexicon_text field in b and a2 is the same in a. The results I get are really weird. When I dump x, I am not getting a new json_object that contains all the fields in a and b. I get all the objects in b followed by all the objects in a.
Can someone suggest me the right way to do this?
EDIT: Also, is there a way I can do this without loading the schema? Because sometime in future, if the format of any of the files changes (a new field gets added or an existing field gets deleted), I do not want to change the pig script. Is there a way I can do the JOIN without referencing the field position but by accessing the field name? Thanks! )

Answer 1

The behavior is expected since you have specified a FULL outer join.
Remove FULL to only get matching records.See here for FULL outer join.
x = JOIN b BY b19, a BY a2;