amol- commented on a change in pull request #75:
URL: https://github.com/apache/arrow-cookbook/pull/75#discussion_r712008177
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File path: python/source/schema.rst
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@@ -108,4 +108,87 @@ as far as they are compatible
pyarrow.Table
col1: int32
col2: string
- col3: double
\ No newline at end of file
+ col3: double
+
+Merging multiple schemas
+========================
+
+When you have multiple separate groups of data that you want to combine
+it might be necessary to unify their schemas to create a superset of them
+that applies to all data sources.
+
+.. testcode::
+
+ import pyarrow as pa
+
+ first_schema = pa.schema([
+ ("country", pa.string()),
+ ("population", pa.int32())
+ ])
+
+ second_schema = pa.schema([
+ ("country_code", pa.string()),
+ ("language", pa.string())
+ ])
+
+:func:`unify_schemas` can be used to combine multiple schemas into
+a single one:
+
+.. testcode::
+
+ union_schema = pa.unify_schemas([first_schema, second_schema])
+
+ print(union_schema)
+
+.. testoutput::
+
+ country: string
+ population: int32
+ country_code: string
+ language: string
+
+If the combined schemas have overlapping columns, they can still be combined
+as far as the colliding columns retain the same type (``country_code``):
Review comment:
I actually went in the direction of showing the case where there are no
overlapping columns first because I thought that when talking about "merging"
two things it's easier to get what's going on if you see a perfect union of the
two original collections.
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