Source:
<code>public ParseNode visitLeave(ExistsParseNode node, List<ParseNode> l) throws SQLException { boolean isTopNode = topNode == node; if (isTopNode) { topNode = null; } SubqueryParseNode subqueryNode = (SubqueryParseNode) l.get(0); SelectStatement subquery = fixSubqueryStatement(subqueryNode.getSelectNode()); String rhsTableAlias = ParseNodeFactory.createTempAlias(); JoinConditionExtractor conditionExtractor = new JoinConditionExtractor(subquery, resolver, connection, rhsTableAlias); ParseNode where = subquery.getWhere() == null ? null : subquery.getWhere().accept(conditionExtractor); if (where == subquery.getWhere()) { <START> subquery = NODE_FACTORY.select(subquery, NODE_FACTORY.limit(NODE_FACTORY.literal(1)), null); <END> subqueryNode = NODE_FACTORY.subquery(subquery, false); node = NODE_FACTORY.exists(subqueryNode, node.isNegate()); return super.visitLeave(node, Collections.<ParseNode> singletonList(subqueryNode)); } List<AliasedNode> additionalSelectNodes = conditionExtractor.getAdditionalSelectNodes(); List<AliasedNode> selectNodes = Lists.newArrayListWithExpectedSize(additionalSelectNodes.size() + 1); selectNodes.add(NODE_FACTORY.aliasedNode(ParseNodeFactory.createTempAlias(), LiteralParseNode.ONE)); selectNodes.addAll(additionalSelectNodes); subquery = NODE_FACTORY.select(subquery, true, selectNodes, where); ParseNode onNode = conditionExtractor.getJoinCondition(); TableNode rhsTable = NODE_FACTORY.derivedTable(rhsTableAlias, subquery); JoinType joinType = isTopNode ? (node.isNegate() ? JoinType.Anti : JoinType.Semi) : JoinType.Left; ParseNode ret = isTopNode ? null : NODE_FACTORY.isNull(NODE_FACTORY.column(NODE_FACTORY.table(null, rhsTableAlias), selectNodes.get(0).getAlias(), null), !node.isNegate()); tableNode = NODE_FACTORY.join(joinType, tableNode, rhsTable, onNode, false); return ret; }</code><technical_language>null here? want confirm this is correct</technical_language>

Target:
public ParseNode visitLeave(ExistsParseNode node, List<ParseNode> l) throws SQLException { boolean isTopNode = topNode == node; if (isTopNode) { topNode = null; } SubqueryParseNode subqueryNode = (SubqueryParseNode) l.get(0); SelectStatement subquery = fixSubqueryStatement(subqueryNode.getSelectNode()); String rhsTableAlias = ParseNodeFactory.createTempAlias(); JoinConditionExtractor conditionExtractor = new JoinConditionExtractor(subquery, resolver, connection, rhsTableAlias); ParseNode where = subquery.getWhere() == null ? null : subquery.getWhere().accept(conditionExtractor); if (where == subquery.getWhere()) { subquery = NODE_FACTORY.select(subquery, NODE_FACTORY.limit(NODE_FACTORY.literal(1))); subqueryNode = NODE_FACTORY.subquery(subquery, false); node = NODE_FACTORY.exists(subqueryNode, node.isNegate()); return super.visitLeave(node, Collections.<ParseNode> singletonList(subqueryNode)); } List<AliasedNode> additionalSelectNodes = conditionExtractor.getAdditionalSelectNodes(); List<AliasedNode> selectNodes = Lists.newArrayListWithExpectedSize(additionalSelectNodes.size() + 1); selectNodes.add(NODE_FACTORY.aliasedNode(ParseNodeFactory.createTempAlias(), LiteralParseNode.ONE)); selectNodes.addAll(additionalSelectNodes); subquery = NODE_FACTORY.select(subquery, true, selectNodes, where); ParseNode onNode = conditionExtractor.getJoinCondition(); TableNode rhsTable = NODE_FACTORY.derivedTable(rhsTableAlias, subquery); JoinType joinType = isTopNode ? (node.isNegate() ? JoinType.Anti : JoinType.Semi) : JoinType.Left; ParseNode ret = isTopNode ? null : NODE_FACTORY.isNull(NODE_FACTORY.column(NODE_FACTORY.table(null, rhsTableAlias), selectNodes.get(0).getAlias(), null), !node.isNegate()); tableNode = NODE_FACTORY.join(joinType, tableNode, rhsTable, onNode, false); return ret; }