Function: grok_validate_order_by_columns

Overview

This function validates that specified order-by columns exist in a source table and contain data that can be parsed as timestamps, ensuring they can be used for deterministic ordering.

Schema

config.grok_validate_order_by_columns

Parameters

source_schema (text): Schema containing the source table
source_table (text): Name of the source table
order_by_columns (text[]): Array of column names to validate

Return Value

Returns a text array containing warning messages for any issues found:

{
  "Warning: column_name not found in schema.table",
  "Warning: column_name contains unparseable timestamp data: error message"
}

Description

This function validates columns intended for use in ORDER BY clauses, particularly for generating synthetic keys in materialized views. It performs two types of validation:

Existence Check: Verifies each column exists in the specified table
Timestamp Parsing: Tests if each column's data can be parsed as a timestamp

For timestamp parsing, the function attempts to convert the column data using:

TO_TIMESTAMP(SUBSTRING(NULLIF(column, ''), 1, 19), 'YYYY-MM-DD HH24:MI:SS')

This validation approach ensures that:

Columns are valid for the source table
Timestamp columns can be parsed consistently
The ORDER BY clause will produce deterministic results

Timestamp Parsing Details

The timestamp parsing logic:

Uses NULLIF to handle NULL values
Takes only the first 19 characters using SUBSTRING
Uses a fixed format of 'YYYY-MM-DD HH24:MI:SS'

This standardized parsing ensures consistent ordering behavior regardless of the actual format stored in the column.

Error Handling

The function collects warnings without failing, allowing for a complete validation report:

Missing columns generate a warning
Unparseable timestamp data generates a warning with the specific error
If an unexpected error occurs, it returns a general error message

Dependencies

This function is likely called by other functions that create materialized views to validate order-by columns before using them.

Usage Example

SELECT config.grok_validate_order_by_columns(
  'public',
  'customers',
  ARRAY['created_at', 'updated_at']
);

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