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Room Database Migration Utility
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DatabaseMigration.alterTable("user") | |
.addColumn("rowid", "INTEGER", true, 1, null) | |
.makeNotNull("type") | |
.makeNotNull("longitude") | |
.removeColumn("dummy") | |
.changeColumn("name", "text", true, false) | |
.renameIndex("old_name", "new_name") | |
.removeIndex("index_to_remove") | |
.addIndex("index_to_add", "CREATE INDEX index_to_add ON user(type)") | |
.setPrimaryKey("dummy", "name") | |
.execute(database); |
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package cc.gunz.mobilecatalog.database.base; | |
import android.database.Cursor; | |
import java.util.ArrayList; | |
import java.util.Arrays; | |
import java.util.Collections; | |
import java.util.HashMap; | |
import java.util.HashSet; | |
import java.util.LinkedHashMap; | |
import java.util.List; | |
import java.util.Locale; | |
import java.util.Map; | |
import java.util.Set; | |
import androidx.annotation.NonNull; | |
import androidx.annotation.Nullable; | |
import androidx.annotation.RequiresApi; | |
import androidx.room.util.TableInfo; | |
import androidx.sqlite.db.SupportSQLiteDatabase; | |
/** | |
* Utlity class to alter tables during a database migration | |
*/ | |
@RequiresApi(20) | |
public class DatabaseMigration { | |
private final String tableName; | |
private final Set<String> columnsToRemove = new HashSet<>(); | |
private final Map<String, ColumnDefinition> columnsToChange = new HashMap<>(); | |
private List<String> primaryKeyOverride = null; | |
private final Map<String, Boolean> columnsToChangeNullability = new HashMap<>(); | |
private final List<ColumnDefinition> columnsToAdd = new ArrayList<>(); | |
private final Set<String> indicesToRemove = new HashSet<>(); | |
private final Map<String, String> indicesToAdd = new HashMap<>(); | |
private final Map<String, String> indicesToRename = new HashMap<>(); | |
private boolean makeAllNotNull = false; | |
public static DatabaseMigration alterTable(String tablename) { | |
return new DatabaseMigration(tablename); | |
} | |
private DatabaseMigration(String tableName) { | |
this.tableName = tableName; | |
} | |
/** | |
* Adds a new column | |
* | |
* @param columnName name of the column to add | |
* @param datatype sqlite datatype | |
* @param isNotNull whether this column is "not null" | |
* @param primaryKeyPosition position of this column in the primary key, 0 for columns that are not part of the primary key | |
* @param defaultValueExpr SQL expression to define the new contents of the column. if null, the column will not be filled with data | |
*/ | |
public DatabaseMigration addColumn(String columnName, String datatype, boolean isNotNull, int primaryKeyPosition, @Nullable String defaultValueExpr) { | |
columnsToAdd.add(new ColumnDefinition(columnName, datatype, isNotNull, primaryKeyPosition, defaultValueExpr)); | |
return this; | |
} | |
public DatabaseMigration addRowId() { | |
return addColumn("rowid", "INTEGER", true, 1, null); | |
} | |
/** | |
* Changes the datatype of a column while keeping its contents the same | |
* | |
* @param columnName name of the column to change | |
* @param datatype sqlite datatype | |
* @param isNotNull whether this column is "not null" | |
* @param primaryKeyPosition position of this column in the primary key, 0 for columns that are not part of the primary key | |
*/ | |
public DatabaseMigration changeColumn(String columnName, String datatype, boolean isNotNull, int primaryKeyPosition) { | |
return changeColumn(columnName, datatype, isNotNull, primaryKeyPosition, "`" + columnName + "`"); | |
} | |
/** | |
* Changes the datatype of a column | |
* | |
* @param columnName name of the column to change | |
* @param datatype sqlite datatype | |
* @param isNotNull whether this column is "not null" | |
* @param primaryKeyPosition position of this column in the primary key, 0 for columns that are not part of the primary key | |
* @param valueExpr SQL expression to define the new contents of the column. if null, the column will not be filled with data | |
*/ | |
public DatabaseMigration changeColumn(String columnName, String datatype, boolean isNotNull, int primaryKeyPosition, @Nullable String valueExpr) { | |
columnsToChange.put(columnName.toLowerCase(Locale.US), new ColumnDefinition(columnName, datatype, isNotNull, primaryKeyPosition, valueExpr)); | |
return this; | |
} | |
/** | |
* Changes a column definition to be NOT NULL | |
*/ | |
public DatabaseMigration makeNotNull(String... columnNames) { | |
for (String columnName : columnNames) { | |
columnsToChangeNullability.put(columnName.toLowerCase(Locale.US), Boolean.FALSE); | |
} | |
return this; | |
} | |
/** | |
* Changes a column definition to be nullable | |
*/ | |
public DatabaseMigration makeNullable(String... columnNames) { | |
for (String columnName : columnNames) { | |
columnsToChangeNullability.put(columnName.toLowerCase(Locale.US), Boolean.TRUE); | |
} | |
return this; | |
} | |
/** | |
* Changes every column to be nonnull except columns explicitly mentioned in makeNullable | |
*/ | |
public DatabaseMigration makeAllNotNull() { | |
makeAllNotNull = true; | |
return this; | |
} | |
/** | |
* Changes the primary key of the table to the specified array | |
*/ | |
public DatabaseMigration setPrimaryKey(String... primaryKeyColumns) { | |
primaryKeyOverride = Arrays.asList(primaryKeyColumns); | |
return this; | |
} | |
/** | |
* removes a column from the table | |
* | |
* @param columnName the column to remove | |
*/ | |
public DatabaseMigration removeColumn(String columnName) { | |
this.columnsToRemove.add(columnName.toLowerCase(Locale.US)); | |
return this; | |
} | |
/** | |
* removes an index from the table | |
* | |
* @param indexName the index to remove | |
*/ | |
public DatabaseMigration removeIndex(String indexName) { | |
this.indicesToRemove.add(indexName.toLowerCase(Locale.US)); | |
return this; | |
} | |
/** | |
* add an index to the table or changes an existing one | |
* | |
* @param indexName the name of index to add or change | |
* @param sql the complete sql to create the index | |
*/ | |
public DatabaseMigration addIndex(String indexName, String sql) { | |
this.indicesToAdd.put(indexName.toLowerCase(Locale.US), sql); | |
return this; | |
} | |
/** | |
* rename an index | |
* | |
* @param oldName the name of index to rename | |
* @param newName the new name of the index | |
*/ | |
public DatabaseMigration renameIndex(String oldName, String newName) { | |
this.indicesToRename.put(oldName.toLowerCase(Locale.US), newName); | |
return this; | |
} | |
public void execute(SupportSQLiteDatabase database) { | |
TableInfo existingTableInfo = TableInfo.read(database, tableName); | |
Map<String, String> existingIndices = readExistingIndices(database, tableName); | |
List<ColumnDefinition> columns = createNewTable(database, existingTableInfo); | |
copyValuesToNewTable(database, columns); | |
database.execSQL("DROP TABLE `" + tableName + "`"); | |
database.execSQL("ALTER TABLE `__new_" + tableName + "` RENAME TO `" + tableName + "`"); | |
createIndices(database, existingIndices); | |
} | |
private Map<String, String> readExistingIndices(SupportSQLiteDatabase database, String tableName) { | |
try (Cursor cursor = database.query("SELECT name, sql FROM sqlite_master WHERE type='index' AND tbl_name = ?", new String[]{tableName})) { | |
if (cursor.getCount() == 0) | |
return Collections.emptyMap(); | |
Map<String, String> retval = new LinkedHashMap<>(cursor.getCount()); | |
if (cursor.moveToFirst()) { | |
do { | |
String indexName = cursor.getString(0); | |
String sql = cursor.getString(1); | |
if (indexName.startsWith("sqlite_autoindex_")) { | |
continue; | |
} | |
if (sql == null) { | |
if (!indicesToRemove.contains(indexName.toLowerCase(Locale.US))) { | |
throw new UnsupportedOperationException("Could not get index sql for " + indexName); | |
} | |
continue; | |
} | |
retval.put(indexName, sql); | |
} while (cursor.moveToNext()); | |
} | |
return retval; | |
} | |
} | |
private List<ColumnDefinition> createNewTable(SupportSQLiteDatabase database, TableInfo existingTableInfo) { | |
List<ColumnDefinition> retval = new ArrayList<>(); | |
StringBuilder createTableBuilder = new StringBuilder(); | |
createTableBuilder.append("CREATE TABLE `__new_").append(tableName).append("` ("); | |
boolean first = true; | |
for (TableInfo.Column column : existingTableInfo.columns.values()) { | |
if (!columnsToRemove.contains(column.name.toLowerCase(Locale.US))) { | |
if (!first) { | |
createTableBuilder.append(", "); | |
} | |
first = false; | |
ColumnDefinition definition = columnsToChange.get(column.name.toLowerCase(Locale.US)); | |
if (definition == null) { | |
definition = new ColumnDefinition(column.name, column.type, column.notNull, column.primaryKeyPosition, "`" + column.name + "`"); | |
} | |
Boolean newNullability = columnsToChangeNullability.get(column.name.toLowerCase(Locale.US)); | |
if (newNullability == null && makeAllNotNull) { | |
newNullability = false; | |
} | |
if (newNullability != null) { | |
definition = definition.changeIsNotNull(!newNullability); | |
} | |
createTableBuilder.append(definition.getColumnDefinition()); | |
retval.add(definition); | |
} | |
} | |
for (ColumnDefinition columnEntry : columnsToAdd) { | |
if (!first) { | |
createTableBuilder.append(", "); | |
} | |
first = false; | |
createTableBuilder.append(columnEntry.getColumnDefinition()); | |
retval.add(columnEntry); | |
} | |
List<String> primaryKeyColumns; | |
if (primaryKeyOverride != null) { | |
primaryKeyColumns = primaryKeyOverride; | |
} else { | |
List<ColumnDefinition> primaryKeyColumnsDef = new ArrayList<>(); | |
for (ColumnDefinition d : retval) { | |
if (d.primaryKeyPosition != 0) { | |
primaryKeyColumnsDef.add(d); | |
} | |
} | |
Collections.sort(primaryKeyColumnsDef, (c1, c2) -> Integer.compare(c1.primaryKeyPosition, c2.primaryKeyPosition)); | |
primaryKeyColumns = new ArrayList<>(primaryKeyColumnsDef.size()); | |
for (ColumnDefinition columnDefinition : primaryKeyColumnsDef) { | |
primaryKeyColumns.add(columnDefinition.name); | |
} | |
} | |
if (!primaryKeyColumns.isEmpty()) { | |
createTableBuilder.append(", PRIMARY KEY ("); | |
first = true; | |
for (String col : primaryKeyColumns) { | |
if (!first) { | |
createTableBuilder.append(", "); | |
} | |
first = false; | |
createTableBuilder.append(col); | |
} | |
createTableBuilder.append(')'); | |
} | |
createTableBuilder.append(')'); | |
database.execSQL(createTableBuilder.toString()); | |
return retval; | |
} | |
private void copyValuesToNewTable(SupportSQLiteDatabase database, List<ColumnDefinition> columns) { | |
StringBuilder insertBuilder = new StringBuilder(); | |
StringBuilder selectBuilder = new StringBuilder(); | |
insertBuilder.append("INSERT INTO `__new_").append(tableName).append("`("); | |
boolean first = true; | |
for (ColumnDefinition column : columns) { | |
if (column.valueExpr != null) { | |
if (!first) { | |
insertBuilder.append(", "); | |
selectBuilder.append(", "); | |
} | |
first = false; | |
insertBuilder.append(column.name); | |
selectBuilder.append(column.valueExpr); | |
} | |
} | |
insertBuilder.append(") SELECT ").append(selectBuilder).append(" FROM ").append(tableName); | |
database.execSQL(insertBuilder.toString()); | |
} | |
private void createIndices(SupportSQLiteDatabase database, Map<String, String> existingIndices) { | |
for (Map.Entry<String, String> indexEntry : existingIndices.entrySet()) { | |
if (indicesToRemove.contains(indexEntry.getKey().toLowerCase(Locale.US)) || indicesToAdd.containsKey(indexEntry.getKey().toLowerCase(Locale.US))) { | |
continue; | |
} | |
String sql = indexEntry.getValue(); | |
String newName = indicesToRename.get(indexEntry.getKey().toLowerCase(Locale.US)); | |
if (newName != null) { | |
sql = sql.replaceFirst("(?i)^(CREATE\\s+(?:UNIQUE\\s+)?INDEX\\s+)[`']?[_\\w]+[`']?\\b", "$1`" + newName + "`"); | |
} | |
database.execSQL(sql); | |
} | |
for (String sql : indicesToAdd.values()) { | |
database.execSQL(sql); | |
} | |
} | |
private static class ColumnDefinition { | |
final String name; | |
final String type; | |
final boolean isNotNull; | |
final int primaryKeyPosition; | |
private final @Nullable String valueExpr; | |
public ColumnDefinition(String name, String type, boolean isNotNull, int primaryKeyPosition, @Nullable String valueExpr) { | |
this.name = name; | |
this.type = type; | |
this.isNotNull = isNotNull; | |
this.primaryKeyPosition = primaryKeyPosition; | |
this.valueExpr = valueExpr; | |
} | |
public ColumnDefinition changeIsNotNull(boolean isNotNull) { | |
String newValueExpr = this.valueExpr; | |
if (isNotNull && newValueExpr != null) { | |
String defaultVal = "0"; | |
if ("text".equalsIgnoreCase(type)) { | |
defaultVal = "''"; | |
} | |
newValueExpr = "coalesce(" + this.valueExpr + ", " + defaultVal + ")"; | |
} | |
return new ColumnDefinition(name, type, isNotNull, primaryKeyPosition, newValueExpr); | |
} | |
@NonNull | |
public String getColumnDefinition() { | |
return name + " " + type + (isNotNull ? " NOT NULL" : ""); | |
} | |
} | |
} |
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