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  1. MariaDB Server
  2. MDEV-15564

Avoid table rebuild in ALTER TABLE on collation or charset changes

    Details

      Description

      Some character encodings are proper subsets of others. ASCII is a proper subset of latin1 or latin2 or UTF-8. The 3-byte UTF-8 is a proper subset of the 4-byte UTF-8.

      When the character encoding of a column changes such that the storage encoding does not change, we should avoid rebuilding the table.

      Likewise, when the collation of a column changes such that the encoding stays the same, we should avoid rebuilding the table.

      Collations do not matter if the column is not indexed.

      If the collation of an indexed column changes, then the affected indexes may have to be rebuilt. For certain collations we might avoid that as well. For example, changing the encoding and collation from binary 3-byte to binary 4-byte UTF-8 might not require any change.

      When the collation change involves a column that is part of the PRIMARY KEY and we have determined that a collation change is necessary, then the whole table will have to be rebuilt.

        Attachments

          Issue Links

          blocks

          Task - A task that needs to be done. MDEV-11424 Instant ALTER TABLE of failure-free record format changes

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-19524 Server crashes in Bitmap<64u>::is_clear_all / Field_longstr::csinfo_change_allows_instant_alter

          • Major - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. MDEV-18584 Avoid copying when altering CHAR column in InnoDB table

          • Major - Major loss of function.
          • Confirmed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-19284 INSTANT ALTER with ucs2-to-utf16 conversion produces bad data

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-19285 INSTANT ALTER from ascii_general_ci to latin1_general_ci produces corrupt data

          • Major - Major loss of function.
          • Closed
          is blocked by

          Task - A task that needs to be done. MDEV-15563 Instant failure-free data type conversions

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Task - A task that needs to be done. MDEV-17965 Allow instant VARCHAR increase of indexed fields

          • Major - Major loss of function.
          • Closed
          relates to

          Task - A task that needs to be done. MDEV-17773 Avoid table rebuild in ALTER TABLE on collation or charset changes for ENUM and SET

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. MDEV-17301 Change of COLLATE unnecessarily requires ALGORITHM=COPY

          • Critical - Crashes, loss of data, severe memory leak.
          • Stalled

            Activity

              People

              • Assignee:
                kevg Eugene Kosov
                Reporter:
                marko Marko Mäkelä
              • Votes:
                3 Vote for this issue
                Watchers:
                6 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: