Improve Table ergonomics

[ericpan64]

Closes N/A

Background

The Table class is a sparse table (a list of dictionaries with some helper wrappers). Used more DSL-like features to make it neater

Design (high-level)

• Use dot syntax for get, __getitem__, etc.
• A join helper function that is SQL-like and just does left & inner joins

Other notes

---

Summary by cubic

Added new Table methods for extracting data, joining tables, and dot notation access, making data manipulation easier and more flexible.

• New Features
• Added extract and from_path methods for pulling nested and structured data.
• Implemented join for merging tables with flexible key options and join types.
• Enabled dot notation access for rows (e.g., table["$0.name"]) and columns.
• Updated tests to use new access pattern.

[cubic-dev-ai]

cubic analysis

1 issue found across 4 files • Review in cubic

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[cubic-dev-ai]

Calling super().getitem for keys that do not contain a dot breaks the documented behaviour of allowing column access through table["column"]. When the key is a plain column name (e.g. "name") it should delegate to get(), not to the parent dict, otherwise a KeyError will be raised unless a row happens to share that key. The condition should also treat any key that is not a row identifier (doesn't start with "$") as a path expression.

Prompt for AI agents

Address the following comment on chidian/table.py at line 759:

<comment>Calling super().__getitem__ for keys that do not contain a dot breaks the documented behaviour of allowing column access through table[&quot;column&quot;]. When the key is a plain column name (e.g. &quot;name&quot;) it should delegate to get(), not to the parent dict, otherwise a KeyError will be raised unless a row happens to share that key. The condition should also treat any key that is not a row identifier (doesn&#39;t start with &quot;$&quot;) as a path expression.</comment>

<file context>
@@ -335,6 +335,434 @@ def group_by(self, path: str) -&gt; dict[Any, &quot;Table&quot;]:
 
         return {key: Table(rows) for key, rows in groups.items()}
 
+    def extract(self, path: str) -&gt; &quot;Table&quot;:
+        &quot;&quot;&quot;
+        Extract values from all rows using a path and return as a new Table.
+
+        This method is particularly useful for extracting nested structures
+        like FHIR Bundle entries or other collections within your data.
</file context>

Suggested change

	if "." in key:
	if "." in key or not key.startswith("$"):