Migrating a Massive Legacy Database

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MIGRATING A MASSIVE LEGACY DATABASE

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AGENDA ▸ Moving offices ▸ The ecology of large systems ▸ On keeping track of what you know ▸ Profiting from the unexpected ▸ The perceived value of tests ▸ Aligning goals at the company level ▸ Profiting from the unexpected pt. 2 ▸ Rehearsals ▸ Announcing your intentions

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HOW DO YOU MOVE OFFICES?

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LESSON 1: LARGE TECHNICAL PROJECTS ARE DIFFICULT BECAUSE THEY ARE SOCIAL PROBLEMS

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LESSON 2: LARGE SYSTEMS ARE ECOSYSTEMS

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LESSON 3: KEEP YOUR FACTS CENTRALIZED

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CENTRALIZED FACTS FROM A SINGLE DHALL REPRESENTATION WE… ▸ Created usage diagrams ▸ Sent automated pull requests to other teams ▸ Calculated progress reports ▸ Tracked tables that were migrated to other databases already ▸ Created terraform conﬁguration for DMS

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LESSON 4: EXPLOIT THE UNEXPECTED

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LESSON 5: TESTS WILL SLOW YOU DOWN

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‣ Ordering issues ‣ Queries using GROUP BY ‣ Queries relying on case insensitivity ‣ Type mismatches WASTE ?

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LESSON 6: LONG TERM PLATFORM GOALS DON’T ALWAYS ALIGN WITH SHORT TERM BUSINESS GOALS

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LESSON 7: NEVER LET A CRISIS GO TO WASTE

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LESSON 8: PRACTICE, PRACTICE, PRACTICE

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LESSON 9: COMMUNICATE YOUR INTENT

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