General known issues

Known issues when migrating data from MySQL, Oracle, or PostgreSQL.

This page documents known issues you may encounter and suggested workarounds when migrating data from MySQL, Oracle, or PostgreSQL to YugabyteDB.

Contents

Index on timestamp column should be imported as ASC (Range) index to avoid sequential scans

GitHub: Issue #49

Description: If there is an index on a timestamp column, the index should be imported as a range index automatically, as most queries relying on timestamp columns use range predicates. This avoids sequential scans and makes indexed scans accessible.

Workaround: Manually add the ASC (range) clause to the exported files.

Example

An example schema on the source database is as follows:

CREATE INDEX ON timestamp_demo (ts);

Suggested change to the schema is to add the ASC clause as follows:

CREATE INDEX ON timestamp_demo (ts ASC);

Exporting data with names for tables/functions/procedures using special characters/whitespaces fails

GitHub: Issue #636, Issue #688, Issue #702

Description: If you define complex names for your source database tables/functions/procedures using backticks or double quotes for example, `abc xyz` , `abc@xyz`, or "abc@123", the migration hangs during the export data step.

Workaround: Rename the objects (tables/functions/procedures) on the source database to a name without special characters.

Example

An example schema on the source MySQL database is as follows:

CREATE TABLE `xyz abc`(id int);
INSERT INTO `xyz abc` VALUES(1);
INSERT INTO `xyz abc` VALUES(2);
INSERT INTO `xyz abc` VALUES(3);

The exported schema is as follows:

CREATE TABLE "xyz abc" (id bigint);

The preceding example may hang or result in an error.

Importing with case-sensitive schema names

GitHub: Issue #422

Description: If you migrate your database using a case-sensitive schema name, the migration will fail with a "no schema has been selected" or "schema already exists" error(s).

Workaround: Currently, yb-voyager does not support case-sensitive schema names; all schema names are assumed to be case-insensitive (lower-case). If required, you may alter the schema names to a case-sensitive alternative post-migration using the ALTER SCHEMA command.

Example

An example yb-voyager import-schema command with a case-sensitive schema name is as follows:

yb-voyager import schema --target-db-name voyager
    --target-db-hostlocalhost
    --export-dir .
    --target-db-password password
    --target-db-user yugabyte
    --target-db-schema "\"Test\""

The preceding example will result in an error as follows:

ERROR: no schema has been selected to create in (SQLSTATE 3F000)

Suggested changes to the schema can be done using the following steps:

  1. Change the case sensitive schema name during schema migration as follows:

    yb-voyager import schema --target-db-name voyager
--target-db-hostlocalhost
--export-dir .
--target-db-password password
--target-db-user yugabyte
--target-db-schema test

  2. Alter the schema name post migration as follows:

    ALTER SCHEMA "test" RENAME TO "Test";