Just a quick note about modifying constraints:<\/p>\n
There’s no such thing as Below is a snippet for finding partitions, their CHECK constraints based on a Here’s the gist version for easier reading<\/a>.<\/p>\n The couple things I learned in this process was a nice feature in I didn’t do any optimization of this — just got it working and am now testing it in our stage environment. The final script is going to perform the changes on a month’s worth of partitions at a time to help reduce the chance of deadlocking.<\/p>\n If you have thoughts on how I could have done this more efficiently, let me know in the comments!<\/p>\n","protected":false},"excerpt":{"rendered":" Just a quick note about modifying constraints: There’s no such thing as ALTER CONSTRAINT. So, if you want to safely change a CHECK constraint, like on a partition, you need to DROP and ADD it in a single transaction. Below … Continue reading →<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-4963","post","type-post","status-publish","format-standard","hentry","category-postgresql"],"_links":{"self":[{"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/posts\/4963","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/comments?post=4963"}],"version-history":[{"count":10,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/posts\/4963\/revisions"}],"predecessor-version":[{"id":5009,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/posts\/4963\/revisions\/5009"}],"wp:attachment":[{"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/media?parent=4963"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/categories?post=4963"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.chesnok.com\/daily\/wp-json\/wp\/v2\/tags?post=4963"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}ALTER CONSTRAINT<\/code>. So, if you want to safely change a CHECK<\/code> constraint, like on a partition, you need to DROP<\/code> and ADD<\/code> it in a single transaction.<\/p>\nWHERE<\/code> clause. Then we DROP<\/code> the existing constraint and add back the correct constraint. It doesn’t take much sleuthing to figure out what the problem was. \ud83d\ude42<\/p>\n DO $$\n DECLARE myrecord record;\n DECLARE theweek text;\n BEGIN\n FOR myrecord IN SELECT relname, conname from pg_constraint\n JOIN pg_class ON pg_constraint.conrelid = pg_class.oid\n WHERE consrc ~ 'without' and split_part(relname, '_201', 1)\n IN (select table_name from report_partition_info\n WHERE partition_column = 'date_processed') LIMIT 1\n LOOP\n EXECUTE 'ALTER TABLE ' || quote_ident(myrecord.relname)\n || ' DROP CONSTRAINT IF EXISTS '\n || quote_ident(myrecord.conname) || ';';<\/p>\n\n theweek = substring(myrecord.relname from '........$');\n\n EXECUTE 'ALTER TABLE ' || quote_ident(myrecord.relname)\n || ' ADD CONSTRAINT ' || quote_ident(myrecord.conname)\n || ' CHECK ((date_processed >= timestamptz('\n || quote_literal(to_char(date(theweek), 'YYYY-MM-DD')) || '))'\n || ' AND (date_processed < timestamptz('\n || quote_literal(to_char(date(theweek) + 7, 'YYYY-MM-DD'))\n || ')));';\n\n RAISE NOTICE 'DONE: %', myrecord.relname;\nEND LOOP;\n\nEND$$; \n<\/code><\/pre>\nsubstring()<\/code> allowing me to return the date portion of my partition names easily, and split_part()<\/code> which allowed me to return the parent table name and compare it to my list of partitionable tables for the specific partition column. I recently added support for partitioning on a different column for certain tables, so I have to differentiate for this fix. The string function docs<\/a> are pretty great.<\/p>\n