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refactor: cleanup readme and include list of different cloud providers #58

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Nov 13, 2023
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refactor: cleanup readme and include list of different cloud providers #58

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refactor: cleanup readme and include list of different cloud providers
jack-robson Oct 20, 2023
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Update README.md
simoneb Nov 13, 2023
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34 changes: 18 additions & 16 deletions README.md
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Expand Up @@ -2,15 +2,13 @@

![](https://github.com/nearform/temporal_tables/workflows/ci/badge.svg)

This is an attempt to rewrite the postgresql [temporal_tables](https://github.com/arkhipov/temporal_tables) extension in PL/pgSQL, without the need for external c extension.
This rewrite aims to provide a temporal tables solution in PL/pgSQL, targeting AWS RDS, Google Cloud SQL, and Azure Database for PostgreSQL where custom C extensions aren't permitted.

The goal is to be able to use it on AWS RDS and other hosted solutions, where using custom extensions or c functions is not an option.
The script in versioning_function.sql serves as a direct substitute.
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The version provided in `versioning_function.sql` is a drop-in replacement.
For a speedier but riskier option, `versioning_function_nochecks.sql` is 2x faster due to the absence of validation checks.

The version in `versioning_function_nochecks.sql` is similar to the previous one, but all validation checks have been removed. This version is 2x faster than the normal one, but more dangerous and prone to errors.

With time, added some new functionality diverging from the original implementations. New functionalities are however still retro-compatible:
Over time, new features have been introduced while maintaining backward compatibility:

- [Ignore updates with no actual changes](#ignore-unchanged-values)

Expand All @@ -26,6 +24,7 @@ psql temporal_test < versioning_function.sql
```

If you would like to have `set_system_time` function available (more details [below](#system-time)) you should run the following as well:

```sh
psql temporal_test < system_time_function.sql
```
Expand Down Expand Up @@ -106,14 +105,17 @@ Should return something similar to:
| test1 | updated twice | ["2017-08-01 16:10:08.880571+02","2017-08-01 16:10:17.33659+02") |

<a name="system-time"></a>

## Setting custom system time

If you want to take advantage of setting a custom system time you can use the `set_system_time` function. It is a port of the original [set_system_time](https://github.com/arkhipov/temporal_tables#advanced-usage).
The function accepts string representation of timestamp in the following format: `YYYY-MM-DD HH:MI:SS.MS.US` - where hours are in 24-hour format 00-23 and the MS (milliseconds) and US (microseconds) portions are optional.
The function accepts string representation of timestamp in the following format: `YYYY-MM-DD HH:MI:SS.MS.US` - where hours are in 24-hour format 00-23 and the MS (milliseconds) and US (microseconds) portions are optional.
Same as the original function, calling it with `null` will reset to default setting (using the CURRENT_TIMESTAMP):

```sql
SELECT set_system_time(null);
```

Below is an example on how to use this function (continues using the example from above):

Create the set_system_time function:
Expand All @@ -123,6 +125,7 @@ psql temporal_test < system_time_function.sql
```

Set a custom value for the system time:

```sql
SELECT set_system_time('1999-12-31 23:59:59');
```
Expand All @@ -146,15 +149,14 @@ SELECT * FROM subscriptions_history;

Should return something similar to:

name | state | sys_period
----- | ------------- | -------------------------------------------------------------------
test1 | inserted | ["2017-08-01 16:09:45.542983+02","2017-08-01 16:09:54.984179+02")
test1 | updated | ["2017-08-01 16:09:54.984179+02","2017-08-01 16:10:08.880571+02")
test1 | updated twice | ["2017-08-01 16:10:08.880571+02","2017-08-01 16:10:17.33659+02")
test2 | inserted | ["1999-12-31 23:59:59+01","1999-12-31 23:59:59.000001+01")
test2 | updated | ["1999-12-31 23:59:59.000001+01","1999-12-31 23:59:59.000002+01")
test2 | updated twice | ["1999-12-31 23:59:59.000002+01","1999-12-31 23:59:59.000003+01")

| name | state | sys_period |
| ----- | ------------- | ----------------------------------------------------------------- |
| test1 | inserted | ["2017-08-01 16:09:45.542983+02","2017-08-01 16:09:54.984179+02") |
| test1 | updated | ["2017-08-01 16:09:54.984179+02","2017-08-01 16:10:08.880571+02") |
| test1 | updated twice | ["2017-08-01 16:10:08.880571+02","2017-08-01 16:10:17.33659+02") |
| test2 | inserted | ["1999-12-31 23:59:59+01","1999-12-31 23:59:59.000001+01") |
| test2 | updated | ["1999-12-31 23:59:59.000001+01","1999-12-31 23:59:59.000002+01") |
| test2 | updated twice | ["1999-12-31 23:59:59.000002+01","1999-12-31 23:59:59.000003+01") |

<a name="additional-features"></a>

Expand Down