Support alias in SQL API

scalar-labs · Apr 4, 2022 · 32b09b8 · 32b09b8
1 parent 6bf9d72
commit 32b09b8
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Showing 14 changed files with 468 additions and 136 deletions.
diff --git a/core/src/main/java/com/scalar/db/sql/DmlStatementExecutor.java b/core/src/main/java/com/scalar/db/sql/DmlStatementExecutor.java
@@ -57,10 +57,13 @@ public ResultSet visit(SelectStatement statement, TransactionCrudOperable transa
 
     Selection selection = convertSelectStatementToSelection(statement, metadata);
 
-    ImmutableList<String> projectedColumnNames =
-        statement.projectedColumnNames.isEmpty()
-            ? ImmutableList.copyOf(metadata.getColumnNames())
-            : statement.projectedColumnNames;
+    ImmutableList<Projection> projections =
+        statement.projections.isEmpty()
+            ? ImmutableList.copyOf(
+                metadata.getColumnNames().stream()
+                    .map(Projection::column)
+                    .collect(Collectors.toList()))
+            : statement.projections;
 
     try {
       if (selection instanceof Get) {
@@ -70,11 +73,11 @@ public ResultSet visit(SelectStatement statement, TransactionCrudOperable transa
                 r ->
                     (ResultSet)
                         new ResultIteratorResultSet(
-                            Collections.singletonList(r).iterator(), projectedColumnNames))
+                            Collections.singletonList(r).iterator(), projections))
             .orElse(EmptyResultSet.INSTANCE);
       } else {
         List<Result> results = transaction.scan((Scan) selection);
-        return new ResultIteratorResultSet(results.iterator(), projectedColumnNames);
+        return new ResultIteratorResultSet(results.iterator(), projections);
       }
     } catch (CrudConflictException e) {
       throw new TransactionConflictException("Conflict happened during selecting a record", e);
@@ -136,13 +139,16 @@ private Selection convertSelectStatementToSelection(
     ImmutableListMultimap<String, Predicate> predicatesMap =
         Multimaps.index(statement.predicates, c -> c.columnName);
 
+    List<String> projectedColumnNames =
+        statement.projections.stream().map(p -> p.columnName).collect(Collectors.toList());
+
     if (SqlUtils.isIndexScan(predicatesMap, metadata)) {
       String indexColumnName = predicatesMap.keySet().iterator().next();
       Scan scan =
           new Scan(
                   createKeyFromPredicatesMap(
                       predicatesMap, Collections.singletonList(indexColumnName)))
-              .withProjections(statement.projectedColumnNames)
+              .withProjections(projectedColumnNames)
               .forNamespace(statement.namespaceName)
               .forTable(statement.tableName);
       if (statement.limit > 0) {
@@ -159,13 +165,13 @@ private Selection convertSelectStatementToSelection(
         clusteringKey = createKeyFromPredicatesMap(predicatesMap, metadata.getClusteringKeyNames());
       }
       return new Get(partitionKey, clusteringKey)
-          .withProjections(statement.projectedColumnNames)
+          .withProjections(projectedColumnNames)
           .forNamespace(statement.namespaceName)
           .forTable(statement.tableName);
     } else {
       Scan scan =
           new Scan(partitionKey)
-              .withProjections(statement.projectedColumnNames)
+              .withProjections(projectedColumnNames)
               .forNamespace(statement.namespaceName)
               .forTable(statement.tableName);
       setClusteringKeyRangeForScan(scan, predicatesMap, metadata);

diff --git a/core/src/main/java/com/scalar/db/sql/Projection.java b/core/src/main/java/com/scalar/db/sql/Projection.java
@@ -0,0 +1,51 @@
+package com.scalar.db.sql;
+
+import com.google.common.base.MoreObjects;
+import java.util.Objects;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+public class Projection {
+
+  public final String columnName;
+  @Nullable public final String alias;
+
+  private Projection(String columnName, @Nullable String alias) {
+    this.columnName = Objects.requireNonNull(columnName);
+    this.alias = alias;
+  }
+
+  public Projection as(String alias) {
+    return new Projection(columnName, alias);
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("columnName", columnName)
+        .add("alias", alias)
+        .toString();
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof Projection)) {
+      return false;
+    }
+    Projection that = (Projection) o;
+    return Objects.equals(columnName, that.columnName) && Objects.equals(alias, that.alias);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(columnName, alias);
+  }
+
+  public static Projection column(String columnName) {
+    return new Projection(columnName, null);
+  }
+}
diff --git a/core/src/main/java/com/scalar/db/sql/ResultIteratorResultSet.java b/core/src/main/java/com/scalar/db/sql/ResultIteratorResultSet.java
@@ -11,34 +11,34 @@
 public class ResultIteratorResultSet implements ResultSet {
 
   private final Iterator<Result> iterator;
-  private final ImmutableList<String> projectedColumnNames;
+  private final ImmutableList<Projection> projections;
 
-  ResultIteratorResultSet(Iterator<Result> iterator, ImmutableList<String> projectedColumnNames) {
+  ResultIteratorResultSet(Iterator<Result> iterator, ImmutableList<Projection> projections) {
     this.iterator = Objects.requireNonNull(iterator);
-    this.projectedColumnNames = Objects.requireNonNull(projectedColumnNames);
+    this.projections = Objects.requireNonNull(projections);
   }
 
   @Override
   public Optional<Record> one() {
     if (iterator.hasNext()) {
-      return Optional.of(new ResultRecord(iterator.next(), projectedColumnNames));
+      return Optional.of(new ResultRecord(iterator.next(), projections));
     }
     return Optional.empty();
   }
 
   @Override
   public Iterator<Record> iterator() {
-    return new ResultIterator(iterator, projectedColumnNames);
+    return new ResultIterator(iterator, projections);
   }
 
   private static class ResultIterator implements Iterator<Record> {
 
     private final Iterator<Result> iterator;
-    private final ImmutableList<String> projectedColumnNames;
+    private final ImmutableList<Projection> projections;
 
-    public ResultIterator(Iterator<Result> iterator, ImmutableList<String> projectedColumnNames) {
+    public ResultIterator(Iterator<Result> iterator, ImmutableList<Projection> projections) {
       this.iterator = iterator;
-      this.projectedColumnNames = projectedColumnNames;
+      this.projections = projections;
     }
 
     @Override
@@ -48,7 +48,7 @@ public boolean hasNext() {
 
     @Override
     public Record next() {
-      return new ResultRecord(iterator.next(), projectedColumnNames);
+      return new ResultRecord(iterator.next(), projections);
     }
   }
 }