When an AWS Glue crawler scans Amazon S3 and detects multiple directories, it uses a heuristic to determine where the root for a table is in the directory structure, and which directories are partitions for the table. In some cases, where the schema detected in two or more directories is similar, the crawler may treat them as partitions instead of separate tables. One way to help the crawler discover individual tables is to add each table's root directory as a data store for the crawler.
The following partitions in Amazon S3 are an example:
s3://amzn-s3-demo-bucket/folder1/table1/partition1/file.txt
s3://amzn-s3-demo-bucket/folder1/table1/partition2/file.txt
s3://amzn-s3-demo-bucket/folder1/table1/partition3/file.txt
s3://amzn-s3-demo-bucket/folder1/table2/partition4/file.txt
s3://amzn-s3-demo-bucket/folder1/table2/partition5/file.txtIf the schema for table1 and table2 are similar, and a
single data source is set to s3://amzn-s3-demo-bucket/folder1/ in AWS Glue,
the crawler may create a single table with two partition columns: one partition column
that contains table1 and table2, and a second partition column
that contains partition1 through partition5.
To have the AWS Glue crawler create two separate tables, set the crawler to have two data
sources, s3://amzn-s3-demo-bucket/folder1/table1/ and
s3://amzn-s3-demo-bucket/folder1/table2, as shown in the following
procedure.
To add an S3 data store to an existing crawler in AWS Glue
Sign in to the AWS Management Console and open the AWS Glue console at https://console.aws.amazon.com/glue/
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In the navigation pane, choose Crawlers.
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Choose the link to your crawler, and then choose Edit.
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For Step 2: Choose data sources and classifiers, choose Edit.
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For Data sources and catalogs, choose Add a data source.
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In the Add data source dialog box, for S3 path, choose Browse.
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Select the bucket that you want to use, and then choose Choose.
The data source that you added appears in the Data sources list.
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Choose Next.
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On the Configure security settings page, create or choose an IAM role for the crawler, and then choose Next.
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Make sure that the S3 path ends in a trailing slash, and then choose Add an S3 data source.
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On the Set output and scheduling page, for Output configuration, choose the target database.
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Choose Next.
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On the Review and update page, review the choices that you made. To edit a step, choose Edit.
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Choose Update.
