7482e65a2d
Add documentation to fix multiple heads Alembic error. Create file contributor/troubleshooting.rst and update contributor/index.rst. Closes-Bug: 1548371 Change-Id: I957bf1c7529f9409d8026f43d5fa8e04b9278d61
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32 lines
1.0 KiB
ReStructuredText
Developer Troubleshooting Guide
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================================
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This guide is intended to provide information on how to resolve common
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problems encountered when developing code for magnum.
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Troubleshooting MySQL
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-----------------------
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When creating alembic migrations, developers might encounter the ``Multiple
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head revisions are present for given argument 'head'`` error.
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This can occur when two migrations revise the same head. For example, the
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developer creates a migration locally but another migration has already been
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accepted and merged into master that revises the same head::
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$ alembic heads
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12345 (your local head)
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67890 (new master head)
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In order to fix this, the developer should update the down_revision of their
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local migration to point to the head of the new migration in master::
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# revision identifiers, used by Alembic.
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revision = '12345'
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down_revision = '67890'
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Now the newest local migration should be head::
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$ alembic heads
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12345 (your local head)
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