public QuerySessionWithViews(QuerySession underlyingQuerySession) {
this.underlyingQuerySession = underlyingQuerySession;
this.correspondingViews = new ArrayList<SymbolicDBView>();
for (int i = 0; i < underlyingQuerySession.numSteps(); i++) {
List<QueryFeature> step = underlyingQuerySession.getSteps().get(i);
assert (step.size() == 1);
StringBuilder viewDefinition = new StringBuilder("CREATE VIEW V" + i + " AS \nSELECT ");
List<String> viewColumns = new ArrayList<String>();
QueryFeature addedSnippet = step.get(0);
if (i == 0) {
F_TableInFrom table = (F_TableInFrom) addedSnippet;
RelationSchema tableSchema = underlyingQuerySession.getSchema().get(table.getTableName());
for (ColumnSchema col : tableSchema.getAttributes()) {
String fullColName = tableSchema.getRelationName() + "." + col;
viewDefinition.append(
fullColName + " AS " + fullColName.replace(".", "") + "_" + i + ",");
viewColumns.add(fullColName.replace(".", "") + "_" + i);
}
viewDefinition.deleteCharAt(viewDefinition.length() - 1); // remove last comma
viewDefinition.append("\nFROM " + table.getTableName() + ";");
} else if (addedSnippet instanceof F_TableInFrom) {
F_TableInFrom addedTable = (F_TableInFrom) addedSnippet;
RelationSchema tableSchema =
underlyingQuerySession.getSchema().get(addedTable.getTableName());
// columns from V_i-1
for (String oldColName : correspondingViews.get(i - 1).columnNames) {
viewDefinition.append(oldColName + " AS " + oldColNameToNewColName(oldColName, i) + ",");
viewColumns.add(oldColNameToNewColName(oldColName, i));
}
// columns from addedTable
for (ColumnSchema col : tableSchema.getAttributes()) {
String fullColName = tableSchema.getRelationName() + "." + col;
viewDefinition.append(
fullColName + " AS " + fullColName.replace(".", "") + "_" + i + ",");
viewColumns.add(fullColName.replace(".", "") + "_" + i);
}
viewDefinition.deleteCharAt(viewDefinition.length() - 1); // remove last comma
viewDefinition.append("\nFROM V" + (i - 1) + "," + addedTable.getTableName() + ";");
} else if (addedSnippet instanceof F_PredicateInWhere) {
F_PredicateInWhere addedPred = (F_PredicateInWhere) addedSnippet;
// columns from V_i-1
for (String oldColName : correspondingViews.get(i - 1).columnNames) {
viewDefinition.append(oldColName + " AS " + oldColNameToNewColName(oldColName, i) + ",");
viewColumns.add(oldColNameToNewColName(oldColName, i));
}
viewDefinition.deleteCharAt(viewDefinition.length() - 1); // remove last comma
viewDefinition.append("\nFROM V" + (i - 1));
viewDefinition.append("\nWHERE " + predicateToViewPredicate(addedPred, (i - 1)) + ";");
} else if (addedSnippet instanceof F_ColumnInGroupBy) {
F_ColumnInGroupBy addedGroupbyCol = (F_ColumnInGroupBy) addedSnippet;
viewDefinition.append(
colNameToViewColName(
addedGroupbyCol.getTableName(), addedGroupbyCol.getColumnName(), i - 1)
+ " AS "
+ colNameToViewColName(
addedGroupbyCol.getTableName(), addedGroupbyCol.getColumnName(), i));
viewDefinition.append(", count(*)");
viewDefinition.append("\nFROM V" + (i - 1));
viewDefinition.append(
"\nGROUP BY "
+ colNameToViewColName(
addedGroupbyCol.getTableName(), addedGroupbyCol.getColumnName(), i - 1));
viewColumns.add(
colNameToViewColName(
addedGroupbyCol.getTableName(), addedGroupbyCol.getColumnName(), i));
}
SymbolicDBView sv = new SymbolicDBView("V" + i, viewDefinition.toString(), viewColumns);
if (i > 0) {
sv.setBackRule(
createBackRule(
underlyingQuerySession.getSchema(),
addedSnippet,
sv,
correspondingViews.get(i - 1),
i));
} else {
sv.setBackRule(
createBackRule(underlyingQuerySession.getSchema(), addedSnippet, sv, null, i));
}
correspondingViews.add(sv);
}
}
private static String createBackRule(
DBSchema baseSchema,
QueryFeature addedSnippet,
SymbolicDBView newView,
SymbolicDBView underlyingView,
int newViewIndex) {
StringBuilder backrule =
new StringBuilder(
"CREATE RULE R_"
+ newView.getViewName()
+ " AS \n"
+ "ON INSERT TO "
+ newView.getViewName()
+ " DO INSTEAD \n");
if (newViewIndex == 0) {
F_TableInFrom addedTable = (F_TableInFrom) addedSnippet;
backrule.append("INSERT INTO " + addedTable.getTableName() + " VALUES (");
// cols from newly added table
RelationSchema tableSchema = baseSchema.get(addedTable.getTableName());
for (ColumnSchema col : tableSchema.getAttributes()) {
backrule.append("NEW." + addedTable.getTableName() + col + "_" + newViewIndex + ",");
}
backrule.deleteCharAt(backrule.length() - 1); // remove last comma
backrule.append(");");
} else if (addedSnippet instanceof F_TableInFrom) {
F_TableInFrom addedTable = (F_TableInFrom) addedSnippet;
backrule.append("(INSERT INTO " + underlyingView.getViewName() + " VALUES (");
// cols from underlying view
for (String col : underlyingView.getColumnNames()) {
backrule.append("NEW." + oldColNameToNewColName(col, newViewIndex) + ",");
}
backrule.deleteCharAt(backrule.length() - 1); // remove last comma
backrule.append("); \nINSERT INTO " + addedTable.getTableName() + " VALUES(");
// cols from newly added table
RelationSchema tableSchema = baseSchema.get(addedTable.getTableName());
for (ColumnSchema col : tableSchema.getAttributes()) {
backrule.append("NEW." + addedTable.getTableName() + col + "_" + newViewIndex + ",");
}
backrule.deleteCharAt(backrule.length() - 1); // remove last comma
backrule.append("));");
} else if (addedSnippet instanceof F_PredicateInWhere) {
F_PredicateInWhere addedPred = (F_PredicateInWhere) addedSnippet;
backrule.append("(INSERT INTO " + underlyingView.getViewName() + " VALUES (");
// cols from underlying view
for (String col : newView.getColumnNames()) {
backrule.append("NEW." + col + ",");
}
backrule.deleteCharAt(backrule.length() - 1); // remove last comma
backrule.append(");");
// add constraint
if (addedPred.rhsIsConst()) {
backrule.append("\nINSERT INTO Constraints VALUES(");
backrule.append(
"NEW."
+ addedPred.getTable1()
+ addedPred.getCol1()
+ "_"
+ newViewIndex
+ ",'"
+ addedPred.getOp()
+ addedPred.getCol2()
+ "')");
} else if (addedPred.lhsIsConst()) {
backrule.append("\nINSERT INTO Constraints VALUES(");
backrule.append(
"NEW."
+ addedPred.getTable2()
+ addedPred.getCol2()
+ "_"
+ newViewIndex
+ ",'"
+ "reverse("
+ addedPred.getOp()
+ ")"
+ addedPred.getCol1()
+ "')");
} else {
backrule.append("\nINSERT INTO VarConstraints VALUES(");
backrule.append(
"NEW."
+ addedPred.getTable1()
+ addedPred.getCol1()
+ "_"
+ newViewIndex
+ ","
+ "NEW."
+ addedPred.getTable2()
+ addedPred.getCol2()
+ "_"
+ newViewIndex
+ ",'"
+ addedPred.getOp()
+ "')");
}
backrule.append("); ");
} else if (addedSnippet instanceof F_ColumnInSelect) {
// direct backrule. since we ignore projects.
backrule.append("INSERT INTO " + underlyingView.getViewName() + " VALUES (");
// cols from underlying view
for (String col : underlyingView.getColumnNames()) {
backrule.append("NEW." + oldColNameToNewColName(col, newViewIndex) + ",");
}
backrule.deleteCharAt(backrule.length() - 1); // remove last comma
backrule.append(");");
}
// problem: grouped by col1 [v1], and then we add col2 to the grouping[v2].
// v2 can not be computed from v1.
return backrule.toString();
}