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fix data loss in the rename column scenario #930

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fix data loss in the rename column scenario #930

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23 changes: 23 additions & 0 deletions go/logic/inspect.go
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Original file line number Diff line number Diff line change
Expand Up @@ -681,8 +681,31 @@ func (this *Inspector) getSharedUniqueKeys(originalUniqueKeys, ghostUniqueKeys [
return uniqueKeys, nil
}

// rebuild columnRenameMap
// handle the issue of data loss in the rename column scenario:
// original column which need rename in the --alter not match the case in the metadata.
// e.g.
// original column `name`, the alter script is change `Name` `aliasName`,
// after gh-ost finished, the value of original column `name` would be lost.
func (this *Inspector) rebuildColumnRenameMap(originalColumns *sql.ColumnList, columnRenameMap map[string]string) map[string]string {
rebuiltColumnRenameMap := make(map[string]string)
for originalColumnk, ghostColumnv := range columnRenameMap {
for i, originalColumn := range originalColumns.Names() {
if strings.EqualFold(originalColumnk, originalColumn) {
rebuiltColumnRenameMap[originalColumn] = ghostColumnv
break
}
if i == originalColumns.Len()-1 {
rebuiltColumnRenameMap[originalColumnk] = ghostColumnv
}
}
}
return rebuiltColumnRenameMap
}

// getSharedColumns returns the intersection of two lists of columns in same order as the first list
func (this *Inspector) getSharedColumns(originalColumns, ghostColumns *sql.ColumnList, originalVirtualColumns, ghostVirtualColumns *sql.ColumnList, columnRenameMap map[string]string) (*sql.ColumnList, *sql.ColumnList) {
columnRenameMap = this.rebuildColumnRenameMap(originalColumns, columnRenameMap)
sharedColumnNames := []string{}
for _, originalColumn := range originalColumns.Names() {
isSharedColumn := false
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