Add date column to v_analytics_product_categories for Funnel (#300)

migrations/000.396.sql

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+-- Add date column to v_analytics_product_categories
+
+-- We want to add a last modified date to v_analytics_product_categories, for Funnel.
+
+-- A row can be modified by any of the following reasons:
+-- 1: when a new product_category mapping is added
+--    -> solved by adding a product_category.inserted column
+-- 2: when category display name is updated (en_GB only)
+--    -> taken from category_texts.name. solved by adding a category_texts.updated column
+-- 3: when category path is updated (en_GB only)
+--    -> also from category_texts.name
+-- 4: when any of the category's parent categories path is updated
+--    -> we skip this for now. not worth the effort as it seems it is not even possible to edit category names in admin at the moment
+--    -> I.e. for the full category path cities-places/geographical-locations/europe/scandinavia/finland/helsinki,
+--       only changes to helsinki will updated the last_modified column.
+--    -> solvable, but complicated, see end of this file for example
+--
+-- The last modified field should be the latest of all date values.
+--
+-- I don't include changes to categories table, I think only the category_texts table is relevant here.
+--
+-- Finally I foresee a problem of how removing a product category mapping will reach Funnel.
+-- If we delete a product_category row - how will they know? (since they use date column to partially read the data)
+
+-- Add category_texts.updated
+ALTER TABLE category_texts ADD COLUMN updated timestamp with time zone NOT NULL DEFAULT now();
+CREATE TRIGGER updated_timestamp BEFORE UPDATE ON public.category_texts FOR EACH ROW EXECUTE PROCEDURE public.updated_timestamp();
+
+-- Add product_category.inserted
+ALTER TABLE product_category ADD COLUMN inserted timestamp with time zone NOT NULL DEFAULT now();
+
+-- Add v_analytics_product_categories.last_updated
+drop view if exists v_analytics_product_categories;
+create view v_analytics_product_categories as
+SELECT DISTINCT tree.id AS category_id,
+                getsafexmlpath(tree.path::character varying, 2) AS category_path,
+                category_texts.name AS category_name,
+                product_category.product_id,
+                greatest(product_category.inserted, category_texts.updated) last_updated
+FROM product_category
+         JOIN categories ON product_category.category_id = categories.id
+         JOIN categories hidden_category ON hidden_category.name::text = 'hidden'::text
+         JOIN v_esales_categorytree_i18n tree ON (tree.lft < categories.lft AND tree.rgt > categories.rgt OR categories.id = tree.id) AND tree.id <> 1 AND (tree.lft < hidden_category.lft OR tree.lft > hidden_category.rgt)
+         JOIN category_texts ON tree.id = category_texts.category_id AND tree.locale_id = category_texts.locale_id
+WHERE tree.locale_id = 3;
+
+grant select on v_analytics_product_categories to datastudio;
+grant select on v_analytics_product_categories to funnel;
+
+
+-- Finally, since we are adding this date field for Funnel's sake, it is of no help if all 320k rows have the exact same date.
+-- Therefore we modify the dates in batches of 10K (Funnel's recommended limit).
+-- We have 320503 rows in v_analytics_product_categories. The dates come from 137739 rows in product_category, and 1665 rows in category_texts
+update product_category set inserted = inserted - (product_id::text || category_id::text)::int % 100 * interval '2 day';
+alter table category_texts disable trigger updated_timestamp;
+update category_texts set updated = updated - (id % 10 + 1) * interval '1 month' where locale_id = 3;
+alter table category_texts enable trigger updated_timestamp;
+-- should create batches of roughly < 10k rows: select last_updated, count(*) from v_analytics_product_categories group by 1;
+
+-- For reference, if we need to include the modification dates for parent categories:
+-- create view v_category_relatives as
+-- select
+--     categories.id category_id,
+--     tree.id related_category_id,
+--     category_texts.name category_name,
+--     category_texts.updated name_update,
+--     getsafexmlpath(tree.path, 2) category_path
+-- from categories
+--          join v_esales_categorytree_i18n tree on tree.locale_id = 3 and (tree.lft < categories.lft and tree.rgt > categories.rgt or categories.id = tree.id) and tree.id <> 1
+--          join category_texts on tree.id = category_texts.category_id
+-- where category_texts.locale_id = 3;
+-- this will get the latest modification date of all relatives of a category:
+-- select max(name_update) from v_category_relatives where category_id = 1094;