Fixed issue with upgrading metadata table in AWS Redshift #1231

[nathanvick]

This fixes the issue where upgrading the metadata table (from Flyway v3.2.1 to v4.0) failed, for at least some installations of AWS Redshift. Redshift does not support altering columns within a table. There are two common workarounds for this:

• Copying data between temp columns: adding a temp column, copying data to the temp column, dropping the original column, adding the updated column, copying data back to the updated column, dropping the temp column
• Copying data between temp tables: renaming the existing table, creating the updated table, copying data to the updated table, dropping the renamed table

This pull request changes the approach from "copying data between temp columns" to "copying data between temp tables" because the former approach requires a commit half way through the process, for some installations of Redshift.

[wgillett]

Looks good to me. I just coded something very similar! I'll see if I can test your change instead.

[wgillett]

Tried it, failed on the table rename. Apparently renaming a table with the schema specified like this doesn't work (the dot in "schema"."table" is considered a syntax error), see:

http://stackoverflow.com/questions/27787741/postgresql-how-to-rename-a-table-inside-a-schema

for reports of a similar problem. Good news is that when I removed the schema, changing the line

ALTER TABLE "${schema}"."${table}" RENAME TO "${schema}"."${table}_flyway4_upgrade";

to

ALTER TABLE "${table}" RENAME TO "${table}_flyway4_upgrade";

then the script worked. That does leave open the possibility of mistakenly renaming a similarly named table in a different schema. Not a problem in my context but don't know if it would make others unhappy.

Walter

Here's the exception I got:

org.flywaydb.core.internal.dbsupport.FlywaySqlScriptException:

Script failed

SQL State : 42601
Error Code : 500310
Message : Amazon Invalid operation: syntax error at or near ".";
Line : 17
Statement : ALTER TABLE "public"."schema_version" RENAME TO "public"."schema_version_flyway4_upgrade"

[nathanvick]

Thanks for the feedback. I'm guessing it would also be possible to keep the schema in the old object name and just remove it from the new object name:

ALTER TABLE "${schema}"."${table}" RENAME TO "${table}_flyway4_upgrade";

I pushed a new commit with just this change: 7050f3f

[wgillett]

That should work fine. I don't have time to retest the full Flyway core right now, but I did confirm on our Redshift DB that while this command fails:

alter table "public"."foo" rename to "public"."fizzle";

this one works - removing the schema qualifier only on the target table name:

alter table "public"."foo" rename to "fizzle";

Thanks.

[axelfontaine]

Thanks Nathan! Merged.

[axelfontaine]

@nathanvick Could you please contact me by email at axel at boxfuse dot com ? Thanks!