fix: issue1875 (#1957)

* fix: issue1875

* fix: code format

---------

Co-authored-by: mjh <[email protected]>

Author: SheldonKubor

src/main/java/net/sf/jsqlparser/statement/alter/Alter.java

@@ -24,6 +24,8 @@ public class Alter implements Statement {
     private Table table;
     private boolean useOnly = false;
 
+    private boolean useTableIfExists = false;
+
     private List<AlterExpression> alterExpressions;
 
     public Table getTable() {
@@ -42,6 +44,19 @@ public void setUseOnly(boolean useOnly) {
         this.useOnly = useOnly;
     }
 
+    public boolean isUseTableIfExists() {
+        return useTableIfExists;
+    }
+
+    public void setUseTableIfExists(boolean useTableIfExists) {
+        this.useTableIfExists = useTableIfExists;
+    }
+
+    public Alter withUseTableIfExists(boolean useTableIfExists) {
+        this.useTableIfExists = useTableIfExists;
+        return this;
+    }
+
     public void addAlterExpression(AlterExpression alterExpression) {
         if (alterExpressions == null) {
             alterExpressions = new ArrayList<AlterExpression>();
@@ -71,7 +86,7 @@ public String toString() {
             b.append("ONLY ");
         }
 
-        if (alterExpressions.size()>0 && alterExpressions.get(0).getOperation()==AlterOperation.RENAME_TABLE && alterExpressions.get(0).isUsingIfExists()) {
+        if (useTableIfExists) {
             b.append("IF EXISTS ");
         }
 
@@ -108,13 +123,15 @@ public Alter withAlterExpressions(List<AlterExpression> alterExpressions) {
     }
 
     public Alter addAlterExpressions(AlterExpression... alterExpressions) {
-        List<AlterExpression> collection = Optional.ofNullable(getAlterExpressions()).orElseGet(ArrayList::new);
+        List<AlterExpression> collection =
+                Optional.ofNullable(getAlterExpressions()).orElseGet(ArrayList::new);
         Collections.addAll(collection, alterExpressions);
         return this.withAlterExpressions(collection);
     }
 
     public Alter addAlterExpressions(Collection<? extends AlterExpression> alterExpressions) {
-        List<AlterExpression> collection = Optional.ofNullable(getAlterExpressions()).orElseGet(ArrayList::new);
+        List<AlterExpression> collection =
+                Optional.ofNullable(getAlterExpressions()).orElseGet(ArrayList::new);
         collection.addAll(alterExpressions);
         return this.withAlterExpressions(collection);
     }

src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java

@@ -70,6 +70,8 @@ public class AlterExpression implements Serializable {
 
     private String truncatePartitionName = null;
 
+    private boolean useIfNotExists = false;
+
     public Index getOldIndex() {
         return oldIndex;
     }
@@ -417,6 +419,19 @@ public AlterExpression withTruncatePartitionName(String truncatePartitionName) {
         return this;
     }
 
+    public boolean isUseIfNotExists() {
+        return useIfNotExists;
+    }
+
+    public void setUseIfNotExists(boolean useIfNotExists) {
+        this.useIfNotExists = useIfNotExists;
+    }
+
+    public AlterExpression withUserIfNotExists(boolean userIfNotExists) {
+        this.useIfNotExists = userIfNotExists;
+        return this;
+    }
+
     @Override
     @SuppressWarnings({"PMD.CyclomaticComplexity", "PMD.NPathComplexity",
             "PMD.ExcessiveMethodLength", "PMD.SwitchStmtsShouldHaveDefault"})
@@ -493,6 +508,10 @@ public String toString() {
                     if (hasColumn) {
                         b.append("COLUMN ");
                     }
+                    if (useIfNotExists
+                            && operation == AlterOperation.ADD) {
+                        b.append("IF NOT EXISTS ");
+                    }
                 }
                 if (useBrackets && colDataTypeList.size() == 1) {
                     b.append(" ( ");

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -6293,7 +6293,7 @@ AlterExpression AlterExpression():
                 |
                 LOOKAHEAD(3) (
                     ( LOOKAHEAD(2) <K_COLUMN> { alterExp.hasColumn(true); } )?
-
+                    [ <K_IF> <K_NOT> <K_EXISTS> { alterExp.setUseIfNotExists(true); } ]
                     (
                         LOOKAHEAD(4) (
                             "(" 
@@ -6625,14 +6625,10 @@ Alter AlterTable():
 {
     <K_TABLE>
     [ <K_ONLY> { alter.setUseOnly(true); } ]
-    [ LOOKAHEAD(2) <K_IF> <K_EXISTS> { usingIfExists = true; } ]
-
+    [ LOOKAHEAD(2) <K_IF> <K_EXISTS> { alter.setUseTableIfExists(true); } ]
     table=Table() { alter.setTable(table); }
 
-    alterExp=AlterExpression() { if (usingIfExists)
-                                    alter.addAlterExpression( alterExp.withUsingIfExists(true) );
-                                  else
-                                    alter.addAlterExpression(alterExp); }
+    alterExp=AlterExpression() { alter.addAlterExpression(alterExp); }
 
     ("," alterExp=AlterExpression() { alter.addAlterExpression(alterExp); } )*
 

src/test/java/net/sf/jsqlparser/statement/alter/AlterTest.java

@@ -988,4 +988,11 @@ public void testIssue1890() throws JSQLParserException {
                 "ALTER TABLE xdmiddle.ft_mid_sop_sms_send_list_daily TRUNCATE PARTITION sum_date";
         assertSqlCanBeParsedAndDeparsed(stmt);
     }
+
+    @Test
+    public void testIssue1875() throws JSQLParserException {
+        String stmt =
+                "ALTER TABLE IF EXISTS usercenter.dict_surgeries ADD COLUMN IF NOT EXISTS operation_grade_id int8 NULL";
+        assertSqlCanBeParsedAndDeparsed(stmt);
+    }
 }