From d1c2effe2ee3f843a92a4dd3ae83ba061ab1894e Mon Sep 17 00:00:00 2001
From: Lukas Eder <lukas.eder@datageekery.com>
Date: Wed, 7 Feb 2024 16:42:44 +0100
Subject: [PATCH] [jOOQ/jOOQ#14307] Emulate LIMIT 0 where not supported

---
 jOOQ/src/main/java/org/jooq/impl/Limit.java      | 16 ++++++++++++----
 .../main/java/org/jooq/impl/SelectQueryImpl.java | 16 ++++++++++++++--
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/jOOQ/src/main/java/org/jooq/impl/Limit.java b/jOOQ/src/main/java/org/jooq/impl/Limit.java
index 1a28b7cff6..af5d6e017c 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Limit.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Limit.java
@@ -319,7 +319,7 @@ final class Limit extends AbstractQueryPart implements UTransient {
                .sql(' ').visit(offsetOrZero)
                .sql(' ').visit(K_ROWS);
 
-        if (!limitZero()) {
+        if (!limitAbsent()) {
             ctx.formatSeparator()
                .visit(K_FETCH_NEXT).sql(' ').visit(limit);
 
@@ -335,7 +335,7 @@ final class Limit extends AbstractQueryPart implements UTransient {
     private final void acceptDefault(Context<?> ctx, CastMode castMode) {
         ctx.castMode(NEVER);
 
-        if (!limitZero())
+        if (!limitAbsent())
             ctx.formatSeparator()
                .visit(K_LIMIT)
                .sql(' ').visit(limit);
@@ -381,19 +381,27 @@ final class Limit extends AbstractQueryPart implements UTransient {
 
 
 
+
+    /**
+     * Whether the limit is absent
+     */
+    final boolean limitAbsent() {
+        return limit == null;
+    }
 
     /**
      * Whether this limit has a limit of zero
      */
     final boolean limitZero() {
-        return limit == null;
+        return !limitAbsent()
+            && Long.valueOf(0L).equals(getLimit());
     }
 
     /**
      * Whether this limit has a limit of one
      */
     final boolean limitOne() {
-        return !limitZero()
+        return !limitAbsent()
             && !withTies()
             && !percent()
             && Long.valueOf(1L).equals(getLimit());
diff --git a/jOOQ/src/main/java/org/jooq/impl/SelectQueryImpl.java b/jOOQ/src/main/java/org/jooq/impl/SelectQueryImpl.java
index c0ef862777..8152e3a4f0 100644
--- a/jOOQ/src/main/java/org/jooq/impl/SelectQueryImpl.java
+++ b/jOOQ/src/main/java/org/jooq/impl/SelectQueryImpl.java
@@ -378,6 +378,8 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
     static final Set<SQLDialect>         NO_SUPPORT_FOR_UPDATE_OF_FIELDS = SQLDialect.supportedBy(MYSQL, POSTGRES, YUGABYTEDB);
     static final Set<SQLDialect>         NO_SUPPORT_UNION_ORDER_BY_ALIAS = SQLDialect.supportedBy(FIREBIRD);
     static final Set<SQLDialect>         NO_SUPPORT_WITH_READ_ONLY       = SQLDialect.supportedBy(CUBRID, DERBY, FIREBIRD, H2, HSQLDB, MARIADB, MYSQL, POSTGRES, SQLITE, YUGABYTEDB);
+    static final Set<SQLDialect>         NO_SUPPORT_LIMIT_ZERO           = SQLDialect.supportedBy(DERBY, HSQLDB);
+
 
 
 
@@ -2156,7 +2158,7 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
 
     @SuppressWarnings("unchecked")
     private final Condition limitWindowFunctionCondition(Field<Integer> limitWindowFunction) {
-        return getLimit().limitZero()
+        return getLimit().limitAbsent()
             ? limitWindowFunction.gt((Field<Integer>) getLimit().getLowerRownum())
             : limitWindowFunction
                     .between((Field<Integer>) getLimit().getLowerRownum().add(inline(1)))
@@ -3469,7 +3471,8 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
 
         if (TRUE.equals(ctx.data(DATA_RENDER_TRAILING_LIMIT_IF_APPLICABLE))) {
             if (actualLimit.isApplicable()) {
-                ctx.visit(actualLimit);
+                if (!(actualLimit.limitZero() && NO_SUPPORT_LIMIT_ZERO.contains(ctx.dialect())))
+                    ctx.visit(actualLimit);
             }
 
             // [#13509] Force a LIMIT clause to prevent optimisation of "unnecessary" ORDER BY
@@ -3560,6 +3563,9 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
 
 
 
+
+
+
 
 
 
@@ -4382,6 +4388,9 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
 
 
 
+        if (NO_SUPPORT_LIMIT_ZERO.contains(ctx.dialect()) && limit.limitZero() && !isGrouping())
+            result.addConditions(falseCondition());
+
         return result;
     }
 
@@ -4517,6 +4526,9 @@ final class SelectQueryImpl<R extends Record> extends AbstractResultQuery<R> imp
         if (isGrouping() && !getOrderBy().isEmpty() && !getSeek().isEmpty() && unionOp.isEmpty())
             result.addConditions(getSeekCondition(ctx));
 
+        if (NO_SUPPORT_LIMIT_ZERO.contains(ctx.dialect()) && limit.limitZero() && isGrouping())
+            result.addConditions(falseCondition());
+
         return result;
     }