lowka commented on code in PR #4221:
URL: https://github.com/apache/ignite-3/pull/4221#discussion_r1721259852
##########
modules/sql-engine/src/main/java/org/apache/ignite/internal/sql/engine/prepare/PlannerHelper.java:
##########
@@ -343,4 +360,171 @@ static boolean hasSubQuery(SqlNode node) {
return super.visit(call);
}
}
+
+
+ /**
+ * Tries to optimize a query that looks like {@code SELECT count(*)}.
+ *
+ * @param planner Planner.
+ * @param txContext Transactional context.
+ * @param node Query node.
+ * @return Plan node with list of aliases, if the optimization is
applicable.
+ */
+ public static @Nullable Pair<IgniteRel, List<String>>
tryOptimizeSelectCount(
+ IgnitePlanner planner,
+ @Nullable QueryTransactionContext txContext,
+ SqlNode node
+ ) {
+ if (txContext != null && txContext.explicitTx() != null) {
+ return null;
+ }
+
+ if (!(node instanceof SqlSelect)) {
+ return null;
+ }
+
+ SqlSelect select = (SqlSelect) node;
+
+ if (select.getGroup() != null
+ || select.getWhere() != null
+ || select.getHaving() != null
+ || select.getQualify() != null
+ || !select.getWindowList().isEmpty()
+ || select.getOffset() != null
+ || select.getFetch() != null) {
+ return null;
+ }
+
+ IgniteSqlToRelConvertor converter = planner.sqlToRelConverter();
+
+ RelOptTable targetTable;
+
+ if (select.getFrom() != null) {
+ SqlNode from = SqlUtil.stripAs(select.getFrom());
+ // Skip non-references such as VALUES ..
+ if (from.getKind() != SqlKind.IDENTIFIER) {
+ return null;
+ }
+
+ targetTable = converter.getTargetTable(select.getFrom());
+ IgniteDataSource dataSource =
targetTable.unwrap(IgniteDataSource.class);
+ if (!(dataSource instanceof IgniteTable)) {
+ return null;
+ }
+ } else {
+ // Try to optimize SELECT count(*) as well
+ targetTable = null;
+ }
+
+ IgniteTypeFactory typeFactory = planner.getTypeFactory();
+
+ // SELECT COUNT(*) ... row type
+ RelDataType countResultType =
typeFactory.createSqlType(SqlTypeName.BIGINT);
+
+ RelDataTypeFactory.Builder inputRowBuilder = new Builder(typeFactory);
+ inputRowBuilder.add("ROWCOUNT", countResultType);
+ RelDataType inputRowType = inputRowBuilder.build();
+
+ RelDataType getCountType =
inputRowType.getFieldList().get(0).getType();
+
+ // Build projection
+ // Rewrites SELECT count(*) ... as Project(exprs = [lit, $0, ... ]),
where $0 references a row that stores a count.
+ // So we can feed results of get count operation into a projection to
compute final results.
+
+ List<RexNode> expressions = new ArrayList<>();
+ List<String> expressionNames = new ArrayList<>();
+ boolean countAdded = false;
+
+ for (SqlNode selectItem : select.getSelectList()) {
+ SqlNode expr = SqlUtil.stripAs(selectItem);
+
+ if (isCountStar(planner.validator(), expr)) {
+ SqlCall call = (SqlCall) expr;
+
+ // Reject COUNT(DISTINCT id), but allow COUNT(DISTINCT 1)
Review Comment:
Thanks. Fixed.
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