Tag archive

#internals

From Code to Output: What Really Happens When You Run Python?

Jun 30, 2026

#python #internals #computerscience #programming

From Code to Output: What Really Happens When You Run Python?

"Python is an interpreted language." You've probably heard this phrase countless times while...

Jun 30, 20263 min read0 reactions0 comments

“PostgreSQL resolves uniqueness through heap tuple visibility”

Jul 9, 2026

#postgres #database #index #internals

“PostgreSQL resolves uniqueness through heap tuple visibility”

I recently commented on Jonathan Lewis’s blog, Savepoint Funny, where I compared how PostgreSQL...

Jul 9, 202612 min read0 reactions1 comments

1.4.10 Planner Hook: When It Fires, How to Use It

Jun 21, 2026

#postgres #database #internals #planner

1.4.10 Planner Hook: When It Fires, How to Use It

Everything from 1.4.1 through 1.4.9 happened inside a single function, standard_planner(). Building...

Jun 21, 20269 min read0 reactions0 comments

1.5.3 Join Nodes: NestLoop, HashJoin, MergeJoin

Jun 21, 2026

#postgres #database #internals #executor

1.5.3 Join Nodes: NestLoop, HashJoin, MergeJoin

A scan node sits at the leaf of the tree and pulls rows from a single table. A join node sits in the...

Jun 21, 20269 min read0 reactions0 comments

Jun 21, 2026

#postgres #database #internals #executor

1.5 Executor: How Results Come Back

By the time 1.4 ends, the planner has produced one PlannedStmt. Inside it is an execution tree built...

Jun 21, 20264 min read0 reactions0 comments

1.4.9 Planner Preprocessing: Subquery Pull-up, Predicate Pushdown, Equivalence Classes

Jun 21, 2026

#postgres #database #internals #planner

1.4.9 Planner Preprocessing: Subquery Pull-up, Predicate Pushdown, Equivalence Classes

So far we have seen the planner build candidate paths and rank them by cost, choose join methods and...

Jun 21, 202612 min read0 reactions0 comments

1.4.6 Aggregate Cost: Choosing HashAgg vs GroupAgg

Jun 21, 2026

#postgres #database #internals #planner

1.4.6 Aggregate Cost: Choosing HashAgg vs GroupAgg

A query like SELECT region, COUNT(*) FROM sales GROUP BY region folds many rows together, collapsing...

Jun 21, 20269 min read0 reactions0 comments

1.4.7 Parallel Cost: When to Go Parallel and How Many Workers

Jun 21, 2026

#postgres #database #internals #planner

1.4.7 Parallel Cost: When to Go Parallel and How Many Workers

The planner weighs how to read a table, how to join, and how to aggregate by cost, and picks the...

Jun 21, 20268 min read0 reactions0 comments

Jun 21, 2026

#postgres #database #internals #query

Closing Chapter 1: From Query to Data

We opened Chapter 1 with a single line, SELECT * FROM users WHERE id = 1. For that line to leave the...

Jun 21, 20262 min read0 reactions0 comments

1.4.4 Join Strategies: Nested Loop, Hash, Merge

Jun 21, 2026

#postgres #database #internals #planner

1.4.4 Join Strategies: Nested Loop, Hash, Merge

The costs in 1.4.2 and 1.4.3 were about how to read a single table. A join combines two tables, and...

Jun 21, 202612 min read0 reactions0 comments

Jun 21, 2026

#postgres #database #internals #executor

1.5.1 The Volcano Iterator Model

In 1.5 we saw the big picture: the executor pulls results up one row at a time. That pulling...

Jun 21, 20268 min read0 reactions0 comments

1.5.4 Aggregation: HashAgg, GroupAgg, Sort-Based

Jun 21, 2026

#postgres #database #internals #executor

1.5.4 Aggregation: HashAgg, GroupAgg, Sort-Based

A scan node reads rows from a table one at a time, and a join node pairs up rows arriving from its...

Jun 21, 20267 min read0 reactions0 comments