Pg for web developer
- 1. PRACTICAL POSGRESQL INDEXES FOR WEB DEVELOPER (RAILS) Long Nguyen 1 — © Employment Hero, 2016
- 2. AGENDA > What is index > Multiple indexes > Gin and Gist > N-gram indexes > Full-text search > Couple of tips 2 — © Employment Hero, 2016
- 3. WHAT IS INDEX ? > Default will be BTree. They are balanced: B-Trees evenly distribute the keys among the nodes, minimizing the number of times we have to follow a pointer from one node to another. Each pointer leads to a child node that contains more or less the same number of keys each other child node does. > What happen when we create a new index is that. PG will create actual physical file in the system to keep track of those indexes. 3 — © Employment Hero, 2016
- 4. MULTIPLE INDEXES > https://wiki.postgresql.org/images/0/0b/ PGforSmarties.pdf 4 — © Employment Hero, 2016
- 5. N-GRAM create extension pg_trgm; select show_trgm('alice'); select * from members where first_name like '%Alice%'; CREATE INDEX CONCURRENTLY index_members_on_firstname_trigram ON members USING gin (first_name gin_trgm_ops); drop index index_members_on_firstname_trigram; 5 — © Employment Hero, 2016
- 6. FULL-TEXT SEARCH > https://kvyengineering.com/2016/03/30/understand- more-about-full-text-search-for-rails-developer/ > From ... like '%name%' ... to full-text search 6 — © Employment Hero, 2016
- 7. GIN & GIST 7 — © Employment Hero, 2016
- 8. DO YOU SQL CAN DO THIS ? ! WITH RECURSIVE x(i) AS ( VALUES(0) UNION ALL SELECT i + 1 FROM x WHERE i < 101), Z(Ix, Iy, Cx, Cy, X, Y, I) AS ( SELECT Ix, Iy, X::float, Y::float, X::float, Y::float, 0 FROM (SELECT -2.2 + 0.031 * i, i FROM x) AS xgen(x,ix) CROSS JOIN (SELECT -1.5 + 0.031 * i, i FROM x) AS ygen(y,iy) UNION ALL SELECT Ix, Iy, Cx, Cy, X * X - Y * Y + Cx AS X, Y * X * 2 + Cy, I + 1 FROM Z WHERE X * X + Y * Y < 16.0 AND I < 27 ), Zt (Ix, Iy, I) AS ( SELECT Ix, Iy, MAX(I) AS I FROM Z GROUP BY Iy, Ix ORDER BY Iy, Ix ) SELECT array_to_string( array_agg( SUBSTRING( ' .,,,-----++++%%%%@@@@#### ', GREATEST(I,1), 1 ) ),'' ) FROM Zt GROUP BY Iy ORDER BY Iy; 8 — © Employment Hero, 2016