This document describes how to use the Spanner migration tool (SMT)to migrate your MySQL schema to Spanner. SMT can read your MySQLschema and convert it to Spanner schema, remove duplicate indexes,and offer schema optimization suggestions.

Before you begin

Ensure you've installed and set up SMT.For more information, seeSet up Spanner migration tool.

Configure schema

Once you've connected your source database and Spanner withSMT, the tool reads your MySQL schema andconverts it to Spanner schema. The tool doesn't convertstored procedures or triggers.

To view a report on the schema conversion, go to theConfigure Schema pageon the web UI and clickView assessment.

This report provides an overall assessment of schema conversion and also providesdetailed table-level and column-level conversion information, suggestions andwarnings, and lists schema elements that couldn't be converted.

Modify schema

On theConfigure Schema page, you can view your source MySQL databaseschema and the draft of the Spanner schema. You can also modifythe converted schema to fit your organization's schema requirements.

You can select tables or indexes, view and manage their schema.

Tables

Select a table you want to modify on theSpanner draft tab onthe web UI. You can drop or restore tables on this tab.For each table you select, you can view the following list of tabs:

• Columns
• Primary key
• Foreign key
• Check constraints
• SQL

Column

TheColumn tab provides information about the columns in the selected table.You can edit the columns in the following ways:

• Modify a column name
• Delete a column
• Change the column's data type
• Add auto-generated IDs
• Modify the default value
• Modify the null property

Besides editing existing columns in the Spanner draft,you can also add new columns to the selected table.

Primary key

You can view and edit the table's primary key from thePrimary key tab inthe following ways:

• Add or remove a column from a primary key
• Change the order of columns in a primary key

You can also use auto-generated columns for primary keys. You can choose oneof the following to create auto-generated columns.

• UUID function:generate a UUID v4 as part of the table's primary keydefault expression.
• Bit-reverse function:map existing integer keys as a bit-reversed sequence.

Foreign key

You can view and edit the table's foreign key from theForeign key tab inthe following ways:

• Change the foreign key constraint name
• Drop the foreign key if you want to use an interleaved table instead
• Convert an interleaved table back to a foreign key

Check constraints

You can view and edit the table's check constraints using theCheck constraints tab in the following ways:

• Change the check constraint name or condition
• Remove the check constraint

SQL

You can view the Spanner data definition languagein the GoogleSQL dialect in theSQL tab.

Indexes

Select an index you want to modify on theSpanner draft tabon the web UI. You can edit the index in the following ways:

• Drop or restore the index
• Add a secondary index
• View the Spanner DDL in theSQL tab.

Prepare migration

Once you complete configuring your schema, you can download the schema as atext file and use the DDL to create the schema in your targetSpanner instance.

To download the schema, go to thePrepare Migration page on the web UI anddo the following:

1. In theMigration Mode drop-down, selectSchema.
2. ClickDownload to download the schema DDL as a text file.