解决PagerUtils.limit 不支持PostgreSQL的bug

参考MySQL的Limit实现，增加PGLimit实现PagerUtils.limit 支持生成PostgreSQL的分页查询sql语句

src/main/java/com/alibaba/druid/sql/dialect/postgresql/ast/stmt/PGSelectQueryBlock.java

@@ -19,11 +19,13 @@ import java.util.ArrayList;
 import java.util.List;
 
 import com.alibaba.druid.sql.ast.SQLExpr;
+import com.alibaba.druid.sql.ast.SQLObjectImpl;
 import com.alibaba.druid.sql.ast.SQLOrderBy;
 import com.alibaba.druid.sql.ast.statement.SQLSelectQueryBlock;
 import com.alibaba.druid.sql.dialect.postgresql.ast.PGSQLObjectImpl;
 import com.alibaba.druid.sql.dialect.postgresql.ast.PGWithClause;
 import com.alibaba.druid.sql.dialect.postgresql.visitor.PGASTVisitor;
+import com.alibaba.druid.sql.dialect.postgresql.visitor.PGOutputVisitor;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class PGSelectQueryBlock extends SQLSelectQueryBlock {
@@ -247,5 +249,63 @@ public class PGSelectQueryBlock extends SQLSelectQueryBlock {
             visitor.endVisit(this);
         }
     }
+    public static class PGLimit extends SQLObjectImpl implements SQLExpr {
+
+        public PGLimit(){
+
+        }
+
+        private SQLExpr rowCount;
+        private SQLExpr offset;
+
+        public SQLExpr getRowCount() {
+            return rowCount;
+        }
+
+        public void setRowCount(SQLExpr rowCount) {
+            if (rowCount != null) {
+                rowCount.setParent(this);
+            }
+            this.rowCount = rowCount;
+        }
+
+        public SQLExpr getOffset() {
+            return offset;
+        }
+
+        public void setOffset(SQLExpr offset) {
+            if (offset != null) {
+                offset.setParent(this);
+            }
+            this.offset = offset;
+        }
+
+        @Override
+        protected void accept0(SQLASTVisitor visitor) {
+            if (visitor instanceof PGASTVisitor) {
+            	PGASTVisitor pgVisitor = (PGASTVisitor) visitor;
+
+                if (pgVisitor.visit(this)) {
+                    if (pgVisitor instanceof PGOutputVisitor)
+                    {
+                        PGOutputVisitor pgv = (PGOutputVisitor) pgVisitor;
+                        pgv.print(this.rowCount.toString());
+                        if (this.offset != null)
+                        {
+                            pgv.print(" OFFSET ");
+                            pgv.print(this.offset.toString());
+                        }
+                    }
+                    else
+                    {
+                        acceptChild(visitor, offset);
+                        acceptChild(visitor, rowCount);
+                    }
+                }
+                pgVisitor.endVisit(this);
+            }
+        }
+
+    }
 
 }

src/main/java/com/alibaba/druid/sql/dialect/postgresql/visitor/PGASTVisitor.java

@@ -27,6 +27,10 @@ import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGUpdateStatement;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public interface PGASTVisitor extends SQLASTVisitor {
+	
+	boolean visit(PGSelectQueryBlock.PGLimit x);
+
+	void endVisit(PGSelectQueryBlock.PGLimit x);
 
     void endVisit(PGSelectQueryBlock x);
 

src/main/java/com/alibaba/druid/sql/dialect/postgresql/visitor/PGASTVisitorAdapter.java

@@ -24,6 +24,7 @@ import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGInsertStatement;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.FetchClause;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.ForClause;
+import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.PGLimit;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.WindowClause;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectStatement;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGUpdateStatement;
@@ -156,4 +157,14 @@ public class PGASTVisitorAdapter extends SQLASTVisitorAdapter implements PGASTVi
         return true;
     }
 
+	@Override
+	public boolean visit(PGLimit x) {
+		return true;
+	}
+
+	@Override
+	public void endVisit(PGLimit x) {
+		
+	}
+
 }

src/main/java/com/alibaba/druid/sql/dialect/postgresql/visitor/PGOutputVisitor.java

@@ -27,6 +27,7 @@ import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGInsertStatement;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.FetchClause;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.ForClause;
+import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.PGLimit;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectQueryBlock.WindowClause;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGSelectStatement;
 import com.alibaba.druid.sql.dialect.postgresql.ast.stmt.PGUpdateStatement;
@@ -470,4 +471,14 @@ public class PGOutputVisitor extends SQLASTOutputVisitor implements PGASTVisitor
 
     }
 
+	@Override
+	public boolean visit(PGLimit x) {
+		return true;
+	}
+
+	@Override
+	public void endVisit(PGLimit x) {
+		
+	}
+
 }