Re: Question regarding how databases support atomicity

quot; writes: > > On Friday, May 3, 2024, Siddharth Jain wrote: > >> The way I understand this is that if there is a failure in-between, we > >>> start undoing and reverting the previous operations one by one. > > > Not in PostgreSQL. All work performed is considered provisi

Re: Question regarding how databases support atomicity

On Fri, May 3, 2024 at 8:00 PM Siddharth Jain wrote: > I am trying to sharpen my understanding of databases. Let's say there is > an operation foo as part of the public API that internally translates to > more than 1 operation - I am sure there are examples like this in postgres. >

Re: How do you optimize the disk IO when you cannot assume a file will start at a boundary then?

Thanks Tomas On Thu, Feb 22, 2024 at 3:05 AM Tomas Vondra wrote: > On 2/22/24 02:22, Siddharth Jain wrote: > > Hi All, > > > > I understand the storage layer in databases goes to great lengths to > ensure: > > - a row does not cross a block boundary > > - re

How do you optimize the disk IO when you cannot assume a file will start at a boundary then?

Hi All, I understand the storage layer in databases goes to great lengths to ensure: - a row does not cross a block boundary - read/writes/allocation happen in units of blocks etc. The motivation is that at the OS level, it reads and writes pages (blocks), not individual bytes. I am only

what happens if a failed transaction is not rolled back?

Hi All, i understand when writing application code, we should rollback a transaction that fails to commit. this is typically done in the catch block of a try-catch exception handler. but what if the developer does not rollback the transaction? what happens in that case? note that i am not

Re: Question on SSI - Serializable Snapshot Isolation

ok thanks tom. On Mon, Apr 17, 2023 at 2:39 PM Tom Lane wrote: > Siddharth Jain writes: > > When using SSI <https://wiki.postgresql.org/wiki/SSI>, lets say we have > two > > transactions T1 and T2 and there is a serialization conflict. Postgres > > knows whe

Question on SSI - Serializable Snapshot Isolation

Hi All, When using SSI , lets say we have two transactions T1 and T2 and there is a serialization conflict. Postgres knows when one or the other transaction is doomed to fail [image: image.png] but will not raise serialization error until the transaction

Transaction Rollback errors

Hi All, when my application (Node.js) receives a class 40 error: Class 40 — Transaction Rollback 4 transaction_rollback 40002 transaction_integrity_constraint_violation 40001 serialization_failure 40003 statement_completion_unknown 40P01 deadlock_detectedthen does it mean PG has already

What permissions are needed to drop a column from a table in postgres?

Hi All, What permissions does a user need to be able to drop columns from a table in postgres? I did read this: https://www.postgresql.org/docs/14/sql-grant.html but could not find the answer. Thanks S.

Re: Question on creating keys on partitioned tables

On Fri, Mar 31, 2023 at 9:07 AM Tom Lane wrote: > Siddharth Jain writes: > > I think the two are equivalent. If not, could you please explain why? > > Well, they're formally equivalent if you require there to be only one > X value per partition (ie, PARTITION BY LIST with onl

Re: Question on creating keys on partitioned tables

Thanks Laurenz. I think the two are equivalent. If not, could you please explain why? On Fri, Mar 31, 2023 at 6:46 AM Laurenz Albe wrote: > On Thu, 2023-03-30 at 17:05 -0700, Siddharth Jain wrote: > > I have this question. Say I create a partitioned table on column X. > &g

Question on creating keys on partitioned tables

Hi All, I have this question. Say I create a partitioned table on column X. Option 1: I add a primary key on (X,Y). Y is another column. Even though Y is a globally unique PK (global meaning it is unique across partitions, not just in one partition), Postgres does not allow me to create a PK on

Re: could not bind IPv4 address "127.0.0.1": Address already in use

Thanks Tom. found the problem. On Tue, Mar 7, 2023 at 8:28 PM Tom Lane wrote: > Siddharth Jain writes: > > But when I try to start the server I get this: > > > 2023-03-07 17:16:43.228 PST [25925] LOG: could not bind IPv6 address > > "::1": Address already

could not bind IPv4 address "127.0.0.1": Address already in use

Hi All, I am trying to run Postgres 14 on a Mac OS. I installed Postgres from EDB and ran initdb and it gave me this: ❯ initdb The files belonging to this database system will be owned by user "xxx". This user must also own the server process. The database cluster will be initialized with

Re: How does Postgres store a B-Tree on disk while using the OS file system?

thanks Christophe. will try to go through it. its bit difficult to grasp. On Mon, Mar 6, 2023 at 5:08 PM Christophe Pettus wrote: > > > > On Mar 6, 2023, at 16:24, Siddharth Jain wrote: > > My question: How can it then store a B Tree on disk? I would think > storing a B

How does Postgres store a B-Tree on disk while using the OS file system?

I am trying to sharpen my understanding of Postgres. As I understand, Postgres does not write directly to disk blocks. It uses the file system provided by the OS: https://dba.stackexchange.com/questions/80036/is-there-a-way-to-store-a-postgresql-database-directly-on-a-block-device-not-fi My

Comparing Postgres logical replication to MySQL

Hi All, I am wondering if there is any article comparing Postgres logical replication to MySQL row based replication? https://dev.mysql.com/doc/refman/8.0/en/replication-sbr-rbr.html Are these two equivalent? If not, what are the differences? S.

Re: Does Postgres 14 have a query cache?

Thanks all for the replies. Just wanted to confirm. On Sat, Feb 18, 2023 at 10:45 AM Steven Lembark wrote: > On Sat, 18 Feb 2023 12:43:42 -0600 > Ron wrote: > > > > I think the answer is no but wanted to confirm here. this is what > > > my best friend told me. > > There are caches for prepared

Re: How to use the BRIN index properly?

23, at 13:17, Siddharth Jain wrote: > > > > As I explained in my question that is indeed our dilemma. Our insertion > order will not be equal to index order. i.e., referring to your response: > > > > > who's data is added in the same order as the key in the BRIN ind

Re: How to use the BRIN index properly?

a log table where new records are always being appended > in "timestamp" order). > > It would also be great for history tables where you can pre-sort the data > by, for example, customer_id, and then put the BRIN on customer_id. > > On 2/8/23 13:58, Siddharth Jain wrote: &g

Re: How to use the BRIN index properly?

our insertion order is of course != index order otherwise the question would have been trivial. we use postgres 14 On Wed, Feb 8, 2023 at 11:51 AM Siddharth Jain wrote: > Hello, > > We have large tables with billions of rows in them and want to take > advantage of the BRIN i

How to use the BRIN index properly?

Hello, We have large tables with billions of rows in them and want to take advantage of the BRIN index on them. Issues we are facing: - as I understand, BRIN index is useful only if the data is stored in index order. As an example we want to create a composite BRIN index on 3 columns -

Re: FATAL: database "xxx" does not exist when it does

> > > > using Postgres 14.4, I created a database as the postgres user: >> >> create database xxx; >> >> postgres=> \c xxx >> psql (13.9 (Debian 13.9-0+deb11u1), server 14.4) >> WARNING: psql major version 13, server major version 14. >> Some psql features might not work. >> SSL

Re: How to avoid having to run the GRANT command for newly added tables?

Thanks Christophe. it works. On Wed, Nov 23, 2022 at 12:08 PM Christophe Pettus wrote: > > > > On Nov 23, 2022, at 12:06, Siddharth Jain wrote: > > Is there any way to accomplish what I want? Thanks. > > There is: > > > https://www.postgresql.org/docs/current/sql-alterdefaultprivileges.html >

How to avoid having to run the GRANT command for newly added tables?

Hello - I have a Postgres 14 server. I created a database and then gave all privileges to tables in the database to a user as shown below: grant connect on database testdb to test_user; GRANT all ON ALL TABLES IN SCHEMA "public" TO test_user; I now verified that test_user is able to access an

Re: Some questions about Postgres

Thanks Laurenz. On Fri, Nov 4, 2022 at 1:55 AM Laurenz Albe wrote: > On Thu, 2022-11-03 at 10:42 -0700, Christophe Pettus wrote: > > > On Nov 3, 2022, at 10:38, Siddharth Jain wrote: > > > I read an old article comparing MySQL to Postgres and wanted to get > answer

Re: Some questions about Postgres

Thanks Christophe. Yes that is the article and I read the response as well. On Thu, Nov 3, 2022 at 10:42 AM Christophe Pettus wrote: > > > > On Nov 3, 2022, at 10:38, Siddharth Jain wrote: > > I read an old article comparing MySQL to Postgres and wanted to get > answers t

Some questions about Postgres

Hi all, I am new to Postgres. I read an old article comparing MySQL to Postgres and wanted to get answers to following questions. All questions are w.r.t. Postgres 14: - do postgres secondary indexes point directly to tuples on disk? - does postgres use a separate process for each connection? -

How to load data from CSV into a table that has array types in its columns?

Hello, Given a long list like this: 1,2 2,4 --> 2 appears once 7,9 8,9 5,3 2,5 --> note 2 appears twice I want to load it into this table: create table tbl ( id integer primary key, fids integer[] ) so we will have 2 -> [4,5] where 2 is id and [4,5] are the fids My actual dataset is very