kosiew commented on issue #1142:
URL:
https://github.com/apache/datafusion-python/issues/1142#issuecomment-2969114420
## Context & Problem Statement
- **Current state**
- **Datafusion core repo:** uses `catalog/schema/table`
- **Datafusion Python repo:** uses `catalog/database/table`
- Other usages: `catalog/namespace/table`
- **Problem**
- The inconsistent terminology leads to confusion for users and
contributors, especially as the API matures and more complex catalog operations
become common.
- There is a need for a consistent 3-level hierarchical naming scheme
across all interfaces and repositories.
- **Why does this matter?**
- Clear, consistent naming improves user understanding and reduces errors.
- Aligning the semantics allows better interoperability and documentation
clarity.
- Since many users presently might only have one
schema/database/namespace, now is a good time to change before adoption widens.
---
## Key Terms and Their Semantic Meanings
| Term | Typical Meaning in Databases |
|------------|-------------------------------------------------------------|
| **Catalog**| The highest-level grouping, often corresponds to a data
source or cluster. |
| **Schema** | A logical grouping/container within a catalog, often
corresponding to namespaces for tables (e.g., Postgres schema). |
| **Database**| Sometimes synonymous with catalog (e.g., MySQL: the database
is a catalog), other times a level. |
| **Namespace**| A more generic term representing a logical scope that
contains tables; can be interchangeable with schema or database depending on
system. |
| **Table** | The actual table or data object. |
---
## Exploration of the Three Naming Variants
### 1. `catalog/schema/table`
- **Pros**
- Matches Datafusion core repo convention, supporting consistency in the
core project.
- Matching widespread SQL semantic usage, e.g., Oracle/Postgres where
schema = namespace under catalog.
- Clear semantic distinction: catalog as the source, schema as logical
grouping.
- **Cons**
- `schema` term might confuse users coming from MySQL or systems where
schema=database.
- In some systems, "database" is the term used instead.
### 2. `catalog/database/table`
- **Pros**
- Familiar to users from MySQL, BigQuery, and others that treat "database"
as the middle layer.
- More intuitive for newcomers who think in terms of databases rather than
schemas.
- **Cons**
- Conflicts with Datafusion core (which prefers “schema”).
- "Database" and "catalog" meanings overlap in different systems, risking
ambiguity.
### 3. `catalog/namespace/table`
- **Pros**
- Namespace is generic and can adapt to any system (equivalent to schema
or database).
- Avoids confusion by not tying to concrete DBMS terminology.
- Aligns with abstraction in distributed systems and catalog APIs.
- **Cons**
- Less immediately familiar to SQL users.
- Could add cognitive overhead if users expect more standard terms.
---
## Diagram: How these map onto a conceptual hierarchy
```plaintext
+---------------------------+
| Catalog |
| +-----------------------+ |
| | Schema / Database / | |
| | Namespace | |
| | +-------------------+ | |
| | | Table | | |
| | +-------------------+ | |
| +-----------------------+ |
+---------------------------+
```
- The middle layer is the point of ambiguity: schema / database / namespace.
---
## Recommendations
### Align with Datafusion Core
- Since the **core repo uses `catalog/schema/table`**, and Datafusion is the
source of truth, **standardizing on `catalog/schema/table`** is recommended to
reduce cognitive dissonance.
### Provide Alias or Flexibility in Python Bindings
- For the Python API and other language bindings, consider exposing aliases
or conversion helpers so the user can think in terms of databases or namespaces
if desired.
- Documentation should clearly indicate what "schema" means in Datafusion
parlance.
### Consider Long-Term Evolution
- If the ecosystem grows to support multiple systems with conflicting
terminologies, *consider introducing a configurable abstraction layer* to map
terms more flexibly. For now, keep it simple.
---
## Summary of User Impact
| User Scenario | Impact of Change to
`catalog/schema/table` |
|--------------------------------|----------------------------------------------------|
| Single-schema users | Minimal to no impact; mostly transparent
|
| Multi-schema advanced users | Gains clarity and consistency
|
| Users from MySQL-style systems | Need to adapt terminology slightly, but
this is common in cross-platform tools |
| Documentation and tooling | Greater consistency and clarity
|
---
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