Add section to README describing PCollections #35012
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This commit adds a new section titled 'Working with PCollections' to the main README.md file. The section explains: - What a PCollection is. - How PCollections are created (from in-memory data and external sources). - Key characteristics of PCollections (immutability, element type, bounded vs. unbounded). - A brief overview of common operations performed on PCollections, leading into PTransforms.
Previously, BigQueryAvroUtils.toGenericAvroSchema used a static namespace
('org.apache.beam.sdk.io.gcp.bigquery') for all generated Avro record schemas,
including those for nested structures. This caused an org.apache.avro.SchemaParseException
if two record fields with the same simple name (e.g., 'identifier') appeared at
different levels of nesting within a BigQuery schema, as they would both attempt
to define an Avro record type with the same full name (e.g.,
'org.apache.beam.sdk.io.gcp.bigquery.identifier').
This commit refactors the Avro schema generation logic:
1. It introduces a recursive helper method, toGenericAvroSchemaRecursive,
that takes the current namespace and a Schema.Names context as parameters.
2. When a nested record is encountered, the namespace for its Avro record type
is now derived from the full name of its parent Avro record type.
For example, a field 'nestedRec' inside an Avro record 'my.parentRec'
will result in an Avro record type named 'nestedRec' within the
namespace 'my.parentRec'. Its full Avro name becomes 'my.parentRec.nestedRec'.
3. A utility method sanitizeNameForAvro is added to ensure that names derived
from BigQuery fields are valid for use in Avro record and field names.
This change ensures that even if multiple BigQuery fields share the same simple
name, their corresponding Avro record types will have unique full names if
their parent structures are different, thus resolving the SchemaParseException.
Addresses issues similar to the one described where nested fields named 'identifier'
caused a type redefinition error when converting to Avro schema.
Previously, BigQueryAvroUtils.toGenericAvroSchema used a static namespace
('org.apache.beam.sdk.io.gcp.bigquery') for all generated Avro record schemas,
including those for nested structures. This caused an org.apache.avro.SchemaParseException
if two record fields with the same simple name (e.g., 'identifier') appeared at
different levels of nesting within a BigQuery schema, as they would both attempt
to define an Avro record type with the same full name (e.g.,
'org.apache.beam.sdk.io.gcp.bigquery.identifier').
This commit refactors the Avro schema generation logic:
1. It introduces a recursive helper method, toGenericAvroSchemaRecursive,
that takes the current namespace and a Schema.Names context as parameters.
2. When a nested record is encountered, the namespace for its Avro record type
is now derived from the full name of its parent Avro record type.
For example, a field 'nestedRec' inside an Avro record 'my.parentRec'
will result in an Avro record type named 'nestedRec' within the
namespace 'my.parentRec'. Its full Avro name becomes 'my.parentRec.nestedRec'.
3. A utility method sanitizeNameForAvro is added to ensure that names derived
from BigQuery fields are valid for use in Avro record and field names.
This change ensures that even if multiple BigQuery fields share the same simple
name, their corresponding Avro record types will have unique full names if
their parent structures are different, thus resolving the SchemaParseException.
Addresses issues similar to the one described where nested fields named 'identifier'
caused a type redefinition error when converting to Avro schema.
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Could you justify the code changes here in a Github issue or in an email thread in the dev list ? |
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This commit adds a new section titled 'Working with PCollections' to the main README.md file.
The section explains:
Please add a meaningful description for your change here
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addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, commentfixes #<ISSUE NUMBER>instead.CHANGES.mdwith noteworthy changes.See the Contributor Guide for more tips on how to make review process smoother.
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