Snippet Name: RDS_Postgres_Database_Creation_Error
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Created Date: 2025-06-16 13:12:50
Last Modified Date: 2025-05-31 10:32:06
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Title: RDS Postgres Database Creation Error
Author: user
with an AWs RDS Postgres database, i am simply trying to create a new database. i get the following error: SQL Error [42501]: ERROR: permission denied for tablespace pg_default
ERROR: permission denied for tablespace pg_default
ERROR: permission denied for tablespace pg_default
Author: ChatGPT
In **AWS RDS for PostgreSQL**, database creation is restricted to the **rds_superuser** or the **master user**. If you are receiving a `permission denied for tablespace pg_default` error, it is likely because:
1. **You are not logged in as the RDS master user.**
2. **You are missing the necessary privileges to create a database.**
3. **AWS RDS restricts direct modification of some system objects, including the default tablespace.**
### ???? **Check Your Current User**
Run the following query to determine which user you are currently using:
```sql
SELECT current_user;
```
If this is not the master user, you may lack the required privileges.
### ??? **Solution 1: Log in as the RDS Master User**
If you have access to the master user, switch to it and try creating the database again.
### ??? **Solution 2: Grant Necessary Permissions**
If you **cannot switch to the master user**, you may need to request permissions from the administrator. However, if you have **superuser-like privileges** via `rds_superuser`, you can try:
```sql
GRANT CREATE ON DATABASE postgres TO your_user;
GRANT CREATE ON SCHEMA public TO your_user;
```
### ??? **Solution 3: Use `CREATE DATABASE` Without Tablespace**
AWS RDS does not allow creating custom tablespaces. Instead of specifying a tablespace, simply run:
```sql
CREATE DATABASE mydatabase;
```
This ensures that PostgreSQL automatically assigns the default tablespace.
### ??? **Solution 4: Check AWS RDS Parameter Group**
AWS RDS manages databases with **parameter groups**. If your instance has **customized restrictions**, check your **Parameter Group settings** in the AWS Console:
1. Navigate to **RDS > Parameter Groups**.
2. Check if database creation is restricted.
3. Modify settings if needed (requires admin privileges).
Let me know if you need more details or help troubleshooting! ????
Author: user
this was very helpful, but for some reason, to create a second database named "stackoverflowmini", I had to repeat those same steps again. is that normal? here are my steps: SELECT current_user;
GRANT CREATE ON DATABASE postgres TO postgres;
GRANT CREATE ON SCHEMA public TO postgres;
CREATE DATABASE stackoverflowmini;
Author: ChatGPT
Yes, that behavior is expected in AWS RDS PostgreSQL, and here's why:
### ???? **Understanding AWS RDS Permissions**
1. **Database-Level Permissions Do Not Automatically Apply to New Databases**
- In PostgreSQL, privileges **do not automatically propagate** from one database to another.
- When you created `stackoverflowmini`, the permissions you granted on `postgres` did not carry over to `stackoverflowmini`.
- Each database is isolated in terms of permissions.
2. **Schema Permissions Are Database-Specific**
- The `GRANT CREATE ON SCHEMA public TO postgres;` command **only applies to the `public` schema in the currently connected database**.
- When you create a new database (`stackoverflowmini`), it has its own `public` schema, and you need to **grant permissions again**.
### ??? **Solution: Set Default Privileges for Future Databases**
To avoid having to manually grant permissions each time you create a database, you can set **default privileges** at the role level.
#### **Step 1: Allow Your User to Create Databases**
If you are using a non-master user (e.g., `your_user`), make sure it has the `CREATEDB` privilege:
```sql
ALTER ROLE your_user CREATEDB;
```
#### **Step 2: Set Default Privileges**
Run the following command **as the RDS master user** to ensure that any new databases grant the necessary privileges automatically:
```sql
ALTER DEFAULT PRIVILEGES FOR ROLE postgres GRANT ALL ON SCHEMAS TO postgres;
```
This ensures that **whenever a new database is created, `postgres` will automatically have the necessary permissions on the `public` schema**.
#### **Step 3: Verify Permissions**
Once you've set this up, try creating another test database:
```sql
CREATE DATABASE testdb;
```
Then immediately try:
```sql
\c testdb
SELECT current_user;
CREATE TABLE test_table (id SERIAL PRIMARY KEY);
```
If everything works without needing additional `GRANT` commands, then your default privileges are correctly set.
---
### ???? **Summary**
- Yes, in RDS PostgreSQL, permissions are database-specific.
- The grants you applied to `postgres` do **not** carry over to newly created databases.
- You must explicitly **set default privileges** to avoid repeating the grant process for each new database.
Let me know if you need more details! ????
Author: user
i am getting this error whent rying to change my database context? \c stackoverflow;
SQL Error [42601]: ERROR: syntax error at or near "\"
Position: 1
Author: ChatGPT
The `\c database_name` command is a **psql meta-command** used to switch databases in **interactive psql sessions**. However, AWS RDS **does not provide direct shell access to PostgreSQL** in the same way as a standalone installation, meaning that `\c` might not work in your client.
### ??? **Alternative Ways to Change the Database Context in AWS RDS PostgreSQL**
1. **Use a New Connection**
- Instead of using `\c`, you must explicitly connect to the database using your client (DBeaver, pgAdmin, or any other tool).
- For example, if using `psql` in an EC2 instance or locally:
```sh
psql -h your-rds-endpoint.amazonaws.com -U your_user -d stackoverflowmini
```
- If using **DBeaver**, pgAdmin, or another GUI tool:
- Disconnect from `postgres`.
- Create a new connection with the **"stackoverflowmini"** database selected.
2. **Re-run the Connection String in SQL**
- In clients like **pgAdmin** or **DBeaver**, you may need to execute:
```sql
SELECT current_database(); -- Check current DB
```
Then manually connect to `stackoverflowmini`.
3. **Use PostgreSQL JDBC or ODBC Connections**
- If you are using a script, you must **open a new connection** with the database specified:
```sh
psql "dbname=stackoverflowmini user=your_user host=your-rds-endpoint.amazonaws.com password=your_password"
```
---
### ???? **Why Doesn't `\c` Work?**
- The `\c` command is **not valid SQL**, it???s a **PostgreSQL meta-command** that only works inside the `psql` CLI.
- AWS RDS **does not provide direct shell access**, so certain `psql` commands do not work.
### ??? **Solution: Always Specify the Database When Connecting**
To switch databases, **disconnect and reconnect** using the desired database in your client or script.
Let me know if you need more help! ????
Author: user
in an existing stackoverflow database, there is a role "readaccess", which implies a user that was granted read on all tables. can you help me create that user, with read permisisons?
Author: ChatGPT
Yes! To create a **read-only user** in your **AWS RDS PostgreSQL** instance and grant it **read access** to all tables, follow these steps:
---
### ??? **Step 1: Create the User (Role)**
First, create the user that will be assigned the `readaccess` role.
```sql
CREATE USER readonly_user WITH PASSWORD 'StrongPassword123';
```
> ???? **Security Tip**: Replace `'StrongPassword123'` with a **secure** password.
---
### ??? **Step 2: Grant the User the Existing `readaccess` Role**
Since the `readaccess` role already exists, simply assign it to the new user:
```sql
GRANT readaccess TO readonly_user;
```
At this point, `readonly_user` inherits all the privileges of `readaccess`.
---
### ??? **Step 3: Verify Permissions**
Check the assigned roles for `readonly_user`:
```sql
SELECT rolname, rolsuper, rolcreaterole, rolcreatedb, rolcanlogin
FROM pg_roles
WHERE rolname = 'readonly_user';
```
Then, log in as `readonly_user` and attempt to query a table:
```sql
SET ROLE readonly_user;
SELECT * FROM some_table; -- Replace with an actual table name
```
If you can successfully read data but not modify it, your setup is correct.
---
### ??? **If You Need to Define the `readaccess` Role from Scratch**
If the `readaccess` role does **not already exist**, you can **create it** and grant it read access to all tables.
#### **1?????? Create the `readaccess` Role**
```sql
CREATE ROLE readaccess;
```
#### **2?????? Grant `read` Access to All Tables in the Existing Database**
Replace `your_database` with your actual database name.
```sql
GRANT CONNECT ON DATABASE your_database TO readaccess;
GRANT USAGE ON SCHEMA public TO readaccess;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;
```
#### **3?????? Assign the `readaccess` Role to `readonly_user`**
```sql
GRANT readaccess TO readonly_user;
```
---
### ???? **Summary**
- If `readaccess` already exists, just create the user and assign the role.
- If `readaccess` **does not** exist, create it and grant **read** privileges on all tables.
- Ensure that new tables automatically grant read access with `ALTER DEFAULT PRIVILEGES`.
Let me know if you need additional refinements! ????
Author: user
ahh, i am a little confused. is 'readaccess' a built in role, the way db_datareader is in SQL Server?
Author: ChatGPT
No, **`readaccess` is NOT a built-in role in PostgreSQL**, unlike `db_datareader` in SQL Server.
### ???? **Understanding Roles in PostgreSQL vs. SQL Server**
| Feature | SQL Server (`db_datareader`) | PostgreSQL (`readaccess`) |
|------------------|---------------------------|---------------------------|
| **Built-in Role?** | ??? Yes (predefined in every DB) | ??? No (must be manually created) |
| **Applies to?** | Specific Database | Specific Database (unless globally set) |
| **Includes Schema Permissions?** | Yes, automatically | No, must be explicitly granted per schema |
| **Affects Future Tables?** | Yes | No (unless `ALTER DEFAULT PRIVILEGES` is set) |
---
### ??? **What is `readaccess` in Your Case?**
Since `readaccess` is not built-in, someone manually created it as a **custom role** in your AWS RDS PostgreSQL instance.
To check its actual permissions, run:
```sql
SELECT grantee, privilege_type, table_schema, table_name
FROM information_schema.role_table_grants
WHERE grantee = 'readaccess';
```
If it doesn't exist, then the role needs to be created first.
---
### ???? **How to Create `readaccess` Manually**
If `readaccess` does not exist in your system, **you need to create it and grant read access**:
```sql
-- Step 1: Create the Role (No Login, Just a Group)
CREATE ROLE readaccess;
-- Step 2: Grant Read-Only Access to Existing Tables
GRANT CONNECT ON DATABASE your_database TO readaccess;
GRANT USAGE ON SCHEMA public TO readaccess;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;
-- Step 3: Ensure Future Tables Also Grant Read Access
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;
```
Then, assign `readonly_user` to this role:
```sql
GRANT readaccess TO readonly_user;
```
---
### ??? **If `readaccess` Already Exists**
If the role is **already there**, simply create a new user and assign it:
```sql
CREATE USER readonly_user WITH PASSWORD 'StrongPassword123';
GRANT readaccess TO readonly_user;
```
---
### ???? **Final Thoughts**
- **`readaccess` is NOT built-in** like `db_datareader` in SQL Server.
- It must be **manually created** and **explicitly granted privileges**.
- Permissions **don???t auto-apply to new tables** unless `ALTER DEFAULT PRIVILEGES` is set.
Let me know if you need clarification! ????
Author: user
ok, for ease of use, can you help me create roles witht eh same names that sql server uses? so i would like the equeivilent custom roles for db_datareader, db_datawriter,db_ddladmin,db_owner, and a custom role named db_execute that has execute on all functions or procedures
Author: ChatGPT
Yes! You can create PostgreSQL **custom roles** that mimic the SQL Server **database roles** (`db_datareader`, `db_datawriter`, `db_ddladmin`, `db_owner`, and `db_execute`).
---
## ???? **Step 1: Create the Equivalent PostgreSQL Roles**
Each role will be **database-specific**, just like in SQL Server.
```sql
-- Create Read-Only Role (Equivalent to db_datareader)
CREATE ROLE db_datareader;
GRANT CONNECT ON DATABASE your_database TO db_datareader;
GRANT USAGE ON SCHEMA public TO db_datareader;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO db_datareader;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO db_datareader;
-- Create Write-Only Role (Equivalent to db_datawriter)
CREATE ROLE db_datawriter;
GRANT CONNECT ON DATABASE your_database TO db_datawriter;
GRANT USAGE ON SCHEMA public TO db_datawriter;
GRANT INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA public TO db_datawriter;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT INSERT, UPDATE, DELETE ON TABLES TO db_datawriter;
-- Create DDL Admin Role (Equivalent to db_ddladmin)
CREATE ROLE db_ddladmin;
GRANT CONNECT ON DATABASE your_database TO db_ddladmin;
GRANT USAGE ON SCHEMA public TO db_ddladmin;
GRANT CREATE, ALTER, DROP ON SCHEMA public TO db_ddladmin;
-- Create Owner-Like Role (Equivalent to db_owner)
CREATE ROLE db_owner;
GRANT CONNECT ON DATABASE your_database TO db_owner;
GRANT ALL PRIVILEGES ON DATABASE your_database TO db_owner;
GRANT ALL PRIVILEGES ON SCHEMA public TO db_owner;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO db_owner;
GRANT ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA public TO db_owner;
GRANT ALL PRIVILEGES ON ALL FUNCTIONS IN SCHEMA public TO db_owner;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT ALL ON TABLES TO db_owner;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT ALL ON SEQUENCES TO db_owner;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT ALL ON FUNCTIONS TO db_owner;
-- Create Execute Role (Equivalent to db_execute)
CREATE ROLE db_execute;
GRANT CONNECT ON DATABASE your_database TO db_execute;
GRANT USAGE ON SCHEMA public TO db_execute;
GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA public TO db_execute;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT EXECUTE ON FUNCTIONS TO db_execute;
```
---
## ???? **Step 2: Assign Users to Roles**
Now, assign users to these roles as needed:
```sql
GRANT db_datareader TO readonly_user;
GRANT db_datawriter TO write_user;
GRANT db_ddladmin TO ddl_admin_user;
GRANT db_owner TO owner_user;
GRANT db_execute TO execution_user;
```
---
## ??? **Summary of Roles and Permissions**
| Role Name | Equivalent SQL Server Role | Permissions Granted |
|-----------------|-------------------------|---------------------|
| **db_datareader** | `db_datareader` | `SELECT` on all tables |
| **db_datawriter** | `db_datawriter` | `INSERT`, `UPDATE`, `DELETE` on all tables |
| **db_ddladmin** | `db_ddladmin` | `CREATE`, `ALTER`, `DROP` on schema |
| **db_owner** | `db_owner` | Full database control (`ALL PRIVILEGES`) |
| **db_execute** | Custom | `EXECUTE` on all functions & procedures |
---
### ???? **Final Thoughts**
- PostgreSQL **does not have built-in database roles** like SQL Server.
- These **custom roles** provide the closest equivalent functionality.
- **New tables and functions will automatically inherit privileges** due to `ALTER DEFAULT PRIVILEGES`.
Would you like any modifications to these roles? ????
Author: user
SQL Server has the concept of a stored procedure, starting with "sp_" and existing in master database, and is marked as a system object ,when called from another database context, inherits the database context of the current database, and pulls from the meta data and database related dmvs there. is there an equivalent in PostGres? for example, i have a function called "check_indexes" in postgres, but I appear to need to deploy that to all 60 databases individually on my postgres instance, which feels like it is redundant and prone to version mitch matches if i need to update and redeploy
Author: ChatGPT
In PostgreSQL, there is **no exact equivalent** to SQL Server's `sp_` system stored procedures that are defined once in `master` and automatically available in all databases while inheriting the caller???s database context. However, there are **alternative approaches** that can achieve a similar effect.
---
## ???? **Options to Make a Function Available Across All Databases in PostgreSQL**
Here are a few ways you can define and use a shared function across multiple databases **without deploying it separately to each one**.
---
### **Option 1: Use the `postgres` Database as a "Master" Utility Database**
Since PostgreSQL does not have a `master` database, many administrators use the **`postgres`** database as a central place for utility functions.
#### ??? **Steps:**
1. **Create your function in the `postgres` database**:
```sql
CREATE FUNCTION postgres.public.check_indexes() RETURNS TABLE (
dbname TEXT,
table_schema TEXT,
table_name TEXT,
index_name TEXT,
index_type TEXT
) AS $$
SELECT
current_database() AS dbname,
schemaname AS table_schema,
tablename AS table_name,
indexname AS index_name,
indexdef AS index_type
FROM pg_indexes;
$$ LANGUAGE sql;
```
2. **Call it from another database using `dblink` or `postgres_fdw`**:
```sql
SELECT * FROM dblink('dbname=postgres', 'SELECT * FROM public.check_indexes()')
AS t(dbname TEXT, table_schema TEXT, table_name TEXT, index_name TEXT, index_type TEXT);
```
???? This allows you to **call the function from any database without deploying it there**.
---
### **Option 2: Use a `pg_catalog` Function to Make It Look Like a System Procedure**
If you want it to behave more like an **sp_ stored procedure**, you can:
- Create the function in **every database**, but place it in the `pg_catalog` schema, which is globally available.
#### ??? **Steps:**
1. **Deploy the function once in each database, inside `pg_catalog`**:
```sql
CREATE FUNCTION pg_catalog.check_indexes() RETURNS TABLE (
dbname TEXT,
table_schema TEXT,
table_name TEXT,
index_name TEXT,
index_type TEXT
) AS $$
SELECT
current_database() AS dbname,
schemaname AS table_schema,
tablename AS table_name,
indexname AS index_name,
indexdef AS index_type
FROM pg_indexes;
$$ LANGUAGE sql;
```
2. **Now you can call it from any database without specifying the schema**:
```sql
SELECT * FROM check_indexes();
```
??? The function will automatically **inherit the current database context**, just like `sp_` procedures in SQL Server.
---
### **Option 3: Use `postgres_fdw` for a Truly Centralized Function**
Instead of deploying the function in all 60 databases, you can:
- Define the function **only once** in a central database.
- Use **`postgres_fdw` (Foreign Data Wrapper)** to access it from other databases.
#### ??? **Steps:**
1. **Enable the Foreign Data Wrapper (One-Time Setup in Each Database)**
```sql
CREATE EXTENSION IF NOT EXISTS postgres_fdw;
```
2. **Create a Foreign Server to the Central Database (e.g., `postgres`)**
```sql
CREATE SERVER postgres_server
FOREIGN DATA WRAPPER postgres_fdw
OPTIONS (host 'localhost', dbname 'postgres', port '5432');
```
3. **Create a Foreign User Mapping**
```sql
CREATE USER MAPPING FOR current_user SERVER postgres_server
OPTIONS (user 'postgres', password 'yourpassword');
```
4. **Create a Foreign Table Reference to the Function**
```sql
CREATE FOREIGN TABLE check_indexes_foreign (
dbname TEXT,
table_schema TEXT,
table_name TEXT,
index_name TEXT,
index_type TEXT
) SERVER postgres_server OPTIONS (schema_name 'public', table_name 'check_indexes');
```
5. **Call the Function in Any Database**
```sql
SELECT * FROM check_indexes_foreign;
```
??? This approach allows **one single function definition** while making it accessible from all databases.
---
## ???? **Which Option Should You Use?**
| Option | Pros | Cons |
|--------|------|------|
| **Use `postgres` as a central utility database** | Simple, avoids redundancy, minimal setup | Requires `dblink` or `postgres_fdw` to query from other DBs |
| **Use `pg_catalog` to make it global per database** | Looks like a system procedure, automatically available | Still requires deployment in each database |
| **Use `postgres_fdw` to make a truly central function** | Only one function exists, no need for re-deployment | More complex setup, requires foreign data wrapper |
---
## ??? **Final Recommendation**
If you want the closest equivalent to SQL Server???s `sp_` procedures **without needing to deploy the function in every database**, I recommend:
1. **Using `postgres_fdw`** if you want the function to exist **only once** in the instance.
2. **Placing the function in `pg_catalog`** if you don???t mind deploying it once per database but want it to behave like a system object.
Would you like me to generate an automation script to deploy the function across all databases? ????