tcl VS PostgreSQL

I've never seen C code as clear and well documented as tcl. E.g. https://github.com/tcltk/tcl/blob/main/generic/tclUtil.c, though more examples in that project are not hard to find.

You're minding your own business, managing AWS infrastructure for a client with a pretty standard e-commerce setup: a Medusa.js backend, a Next.js storefront, and most importantly for this story, a PostgreSQL RDS instance safely stashed away in a private subnet where nothing from the outside world can touch it. Exactly how the AWS gods intended.

Your Database: This is your system's memory. It can be a fast in-memory store like Redis for temporary data (perfect for velocity checks) or a persistent relational database like PostgreSQL for long-term data (like blacklists).

#! /bin/bash set -ex IMG=postgres/test-0.0.1 IMG_ID=`docker images ${IMG} -q` PG_TAG=REL_18_BETA1 if [ "${IMG_ID}" = "" ]; then if [ ! -d "postgres-${PG_TAG}" ]; then wget https://github.com/postgres/postgres/archive/refs/tags/${PG_TAG}.tar.gz && tar -xzf ${PG_TAG}.tar.gz fi ID=991 USR=postgres USR_HOME=/home/postgres cat > Dockerfile << EOF FROM ubuntu:latest RUN groupadd -g ${ID} ${USR} && useradd -r -u ${ID} -g ${USR} ${USR} ADD postgres-${PG_TAG} ${USR_HOME} WORKDIR ${USR_HOME} RUN chown -R ${USR}:${USR} ${USR_HOME} RUN apt-get update && apt-get install -y g++ zlib1g-dev make curl tar gzip perl liblz4-dev libreadline-dev flex bison libicu-dev liburing-dev RUN apt-get install --reinstall -y pkg-config && ./configure --with-liburing --enable-debug --with-lz4 && make -j4 && make all && make install RUN echo "export PATH=/usr/local/pgsql/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" >> /etc/bash.bashrc && \ chown -R ${USR}:${USR} /usr/local/pgsql USER ${USR} EOF docker build -t ${IMG}:latest . rm Dockerfile rm -rf postgres-${PG_TAG} ${PG_TAG}.tar.gz else echo "Image ${IMG} already exists with ID ${IMG_ID}" fi

Choosing the database was straightforward: PostgreSQL. I have the most experience with it, very easy to spin up, has a lot of trust and is open-source (I guess the last two come hand-in-hand).

I was explaining why it is the way that it is. If you'd like your own version of a parser, here's Postgres' [0]. Personally, I really like SQL's syntax and find that it makes sense when reading it.

[0]: https://github.com/postgres/postgres/tree/master/src/backend...

If you’ve never tried PostgreSQL before, the official site is a great starting point: PostgreSQL: The world’s most advanced open source database.

/* https://github.com/postgres/postgres/blob/144ad723a4484927266a316d1c9550d56745ff67/src/backend/optimizer/path/costsize.c#L3375 */ void final_cost_nestloop(PlannerInfo *root, NestPath *path, JoinCostWorkspace *workspace, JoinPathExtraData *extra) { /* ... */ if (path->jpath.path.param_info) path->jpath.path.rows = path->jpath.path.param_info->ppi_rows; else path->jpath.path.rows = path->jpath.path.parent->rows; /* ... */ } /* https://github.com/postgres/postgres/blob/144ad723a4484927266a316d1c9550d56745ff67/src/backend/optimizer/path/costsize.c#L3873 */ void final_cost_mergejoin(PlannerInfo *root, MergePath *path, JoinCostWorkspace *workspace, JoinPathExtraData *extra) { /* ... */ if (path->jpath.path.param_info) path->jpath.path.rows = path->jpath.path.param_info->ppi_rows; else path->jpath.path.rows = path->jpath.path.parent->rows; /* ... */ } /* https://github.com/postgres/postgres/blob/144ad723a4484927266a316d1c9550d56745ff67/src/backend/optimizer/path/costsize.c#L4305 */ void final_cost_hashjoin(PlannerInfo *root, HashPath *path, JoinCostWorkspace *workspace, JoinPathExtraData *extra) { /* ... */ if (path->jpath.path.param_info) path->jpath.path.rows = path->jpath.path.param_info->ppi_rows; else path->jpath.path.rows = path->jpath.path.parent->rows; /* ... */ }

PostgreSQL as database

> As introduced in the previous chapters, all identifers are hashed, thus we can also hash the known keywords at startup and make comparing them very fast.

One trick that postgres uses [1][2] is perfect hashing [3]. Since you know in advance what your keywords are, you can design such hashing functions that for each w(i) in list of i keywords W, h(w(i)) = i. It essentially means no collisions and it's O(i) for the memory requirement.

[1] https://github.com/postgres/postgres/blob/master/src/tools/P...

[2] https://github.com/postgres/postgres/blob/master/src/tools/g...

[3] https://en.wikipedia.org/wiki/Perfect_hash_function

Understanding a database starts with understanding its structure. For PostgreSQL users, one of the most effective ways to visualize and manage your schema is by using an Entity-Relationship Diagram (ERD). Either if you're working with a large legacy database or starting something new, an ER diagram shows how your tables are connected and how your data is organized.