Dimitrie Stefanescu
79 lines
2.7 KiB
JavaScript
79 lines
2.7 KiB
JavaScript
// To make the migration parser happy, we add the customary up and down of knex.
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// They're ignored. A better way would be to conventionally exclude these types of files.
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up = async knex => {}
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down = async knex => {}
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let hashTriggerGenerator = ( tableName, hostField, hashByField ) => `
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CREATE OR REPLACE FUNCTION ${tableName}_hash_${hostField}_update_tg() RETURNS trigger AS $$
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BEGIN
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IF ( tg_op = 'INSERT' OR tg_op = 'UPDATE') AND (( NEW.${hostField} = '') IS NOT FALSE) THEN
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NEW.${hostField} = md5( ${ hashByField ? "NEW." + hashByField : "NEW" }::text );
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RETURN NEW;
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CREATE TRIGGER ${tableName}_hash_${hostField}_update
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BEFORE INSERT OR UPDATE ON ${tableName}
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FOR EACH ROW EXECUTE PROCEDURE ${tableName}_hash_${hostField}_update_tg();
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`
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// ref: https://blog.andyet.com/2016/02/23/generating-shortids-in-postgres/
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let shortIdTriggerGenerator = ( tableName, hostField ) => `
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CREATE OR REPLACE FUNCTION ${tableName}_shortid_update() RETURNS trigger AS $$
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DECLARE
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key TEXT;
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qry TEXT;
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found TEXT;
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BEGIN
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qry := 'SELECT ${hostField} FROM ' || quote_ident(TG_TABLE_NAME) || ' WHERE ${hostField}=';
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LOOP
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-- Generate our string bytes and re-encode as a base64 string.
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key := encode(gen_random_bytes(6), 'base64');
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-- Base64 encoding contains 2 URL unsafe characters by default.
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-- The URL-safe version has these replacements.
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key := replace(key, '/', '_'); -- url safe replacement
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key := replace(key, '+', '-'); -- url safe replacement
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-- Concat the generated key (safely quoted) with the generated query
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-- and run it.
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-- SELECT id FROM "test" WHERE id='blahblah' INTO found
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-- Now "found" will be the duplicated id or NULL.
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EXECUTE qry || quote_literal(key) INTO found;
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-- Check to see if found is NULL.
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-- If we checked to see if found = NULL it would always be FALSE
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-- because (NULL = NULL) is always FALSE.
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IF found IS NULL THEN
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-- If we didn't find a collision then leave the LOOP.
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EXIT;
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END IF;
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-- We haven't EXITed yet, so return to the top of the LOOP
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-- and try again.
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END LOOP;
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-- NEW and OLD are available in TRIGGER PROCEDURES.
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-- NEW is the mutated row that will actually be INSERTed.
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-- We're replacing id, regardless of what it was before
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-- with our key variable.
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NEW.${hostField} = key;
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-- The RECORD returned here is what will actually be INSERTed,
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-- or what the next trigger will get if there is one.
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RETURN NEW;
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END;
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$$ language 'plpgsql';
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CREATE TRIGGER ${tableName}_shortid_update
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BEFORE INSERT ON ${tableName}
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FOR EACH ROW EXECUTE PROCEDURE ${tableName}_shortid_update();
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`
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module.exports = { hashTriggerGenerator, shortIdTriggerGenerator, up, down } |