# Function: grok_validate_matv_inputs

## Overview
This function validates the existence of a materialized view and its source view before performing operations on them, ensuring inputs are valid.

## Schema
`config.grok_validate_matv_inputs`

## Parameters
- `schema_name` (text): Schema containing the materialized view and source view
- `matview_name` (text): Name of the materialized view
- `vtw_name` (text): Optional name of the source view (if not provided, derived from matview_name)

## Return Value
Returns a JSONB object with validation results:

Success case:
```json
{
  "full_matview_name": "schema.matview_name",
  "full_vtw_name": "schema.vtw_name",
  "notes": []
}
```

Error case:
```json
{
  "error": "Materialized view schema.matview_name does not exist",
  "notes": []
}
```

## Description
This function performs input validation before executing operations on materialized views by:

1. Constructing the fully qualified names for the materialized view and source view
2. Checking if the materialized view exists in pg_matviews
3. Checking if the source view exists in either pg_views or pg_tables
4. Returning appropriate error messages if either object is missing

If `vtw_name` is not provided, the function derives it by replacing 'matc_' with 'vtw_' in the materialized view name, following the standard naming convention.

## Validation Checks
The function checks:
- Materialized view existence using the pg_matviews system catalog
- Source view existence using both pg_views and pg_tables system catalogs (handles both views and tables)

## Error Handling
If validation fails, the function returns a descriptive error message indicating which object is missing. If an unexpected error occurs during validation, it returns a generic error message with the exception details.

## Dependencies
This function doesn't call other functions but is likely called by materialized view management functions before performing operations.

## Usage Example
```sql
-- Validate materialized view with automatic source view name derivation
SELECT config.grok_validate_matv_inputs(
  'analytics',
  'matc_daily_sales',
  NULL
);

-- Validate materialized view with explicit source view name
SELECT config.grok_validate_matv_inputs(
  'analytics',
  'matc_daily_sales',
  'custom_source_view'
);
```