feat(hogql): nullish coalescing (#16276)

PostHog · Jun 28, 2023 · 63d6abe · 63d6abe
1 parent 41080c6
commit 63d6abe
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Showing 11 changed files with 1,495 additions and 1,407 deletions.
diff --git a/posthog/hogql/grammar/HogQLLexer.g4 b/posthog/hogql/grammar/HogQLLexer.g4
@@ -288,6 +288,7 @@ LE: '<=';
 LPAREN: '(';
 LT: '<';
 NOT_EQ: '!=' | '<>';
+NULLISH: '??';
 PERCENT: '%';
 PLUS: '+';
 QUERY: '?';

diff --git a/posthog/hogql/grammar/HogQLLexer.interp b/posthog/hogql/grammar/HogQLLexer.interp
diff --git a/posthog/hogql/grammar/HogQLLexer.py b/posthog/hogql/grammar/HogQLLexer.py
diff --git a/posthog/hogql/grammar/HogQLLexer.tokens b/posthog/hogql/grammar/HogQLLexer.tokens
@@ -219,20 +219,21 @@ LE=218
 LPAREN=219
 LT=220
 NOT_EQ=221
-PERCENT=222
-PLUS=223
-QUERY=224
-QUOTE_DOUBLE=225
-QUOTE_SINGLE=226
-RBRACE=227
-RBRACKET=228
-RPAREN=229
-SEMICOLON=230
-SLASH=231
-UNDERSCORE=232
-MULTI_LINE_COMMENT=233
-SINGLE_LINE_COMMENT=234
-WHITESPACE=235
+NULLISH=222
+PERCENT=223
+PLUS=224
+QUERY=225
+QUOTE_DOUBLE=226
+QUOTE_SINGLE=227
+RBRACE=228
+RBRACKET=229
+RPAREN=230
+SEMICOLON=231
+SLASH=232
+UNDERSCORE=233
+MULTI_LINE_COMMENT=234
+SINGLE_LINE_COMMENT=235
+WHITESPACE=236
 'false'=191
 'true'=192
 '->'=201
@@ -255,14 +256,15 @@ WHITESPACE=235
 '<='=218
 '('=219
 '<'=220
-'%'=222
-'+'=223
-'?'=224
-'"'=225
-'\''=226
-'}'=227
-']'=228
-')'=229
-';'=230
-'/'=231
-'_'=232
+'??'=222
+'%'=223
+'+'=224
+'?'=225
+'"'=226
+'\''=227
+'}'=228
+']'=229
+')'=230
+';'=231
+'/'=232
+'_'=233
diff --git a/posthog/hogql/grammar/HogQLParser.g4 b/posthog/hogql/grammar/HogQLParser.g4
@@ -135,6 +135,7 @@ columnExpr
                  | operator=NOT? (LIKE | ILIKE)                                                    // like, notLike, ilike, notILike
                  ) right=columnExpr                                                             # ColumnExprPrecedence3
     | columnExpr IS NOT? NULL_SQL                                                         # ColumnExprIsNull
+    | columnExpr NULLISH columnExpr                                                       # ColumnExprNullish
     | NOT columnExpr                                                                      # ColumnExprNot
     | columnExpr AND columnExpr                                                           # ColumnExprAnd
     | columnExpr OR columnExpr                                                            # ColumnExprOr

diff --git a/posthog/hogql/grammar/HogQLParser.interp b/posthog/hogql/grammar/HogQLParser.interp
diff --git a/posthog/hogql/grammar/HogQLParser.py b/posthog/hogql/grammar/HogQLParser.py
diff --git a/posthog/hogql/grammar/HogQLParser.tokens b/posthog/hogql/grammar/HogQLParser.tokens
@@ -219,20 +219,21 @@ LE=218
 LPAREN=219
 LT=220
 NOT_EQ=221
-PERCENT=222
-PLUS=223
-QUERY=224
-QUOTE_DOUBLE=225
-QUOTE_SINGLE=226
-RBRACE=227
-RBRACKET=228
-RPAREN=229
-SEMICOLON=230
-SLASH=231
-UNDERSCORE=232
-MULTI_LINE_COMMENT=233
-SINGLE_LINE_COMMENT=234
-WHITESPACE=235
+NULLISH=222
+PERCENT=223
+PLUS=224
+QUERY=225
+QUOTE_DOUBLE=226
+QUOTE_SINGLE=227
+RBRACE=228
+RBRACKET=229
+RPAREN=230
+SEMICOLON=231
+SLASH=232
+UNDERSCORE=233
+MULTI_LINE_COMMENT=234
+SINGLE_LINE_COMMENT=235
+WHITESPACE=236
 'false'=191
 'true'=192
 '->'=201
@@ -255,14 +256,15 @@ WHITESPACE=235
 '<='=218
 '('=219
 '<'=220
-'%'=222
-'+'=223
-'?'=224
-'"'=225
-'\''=226
-'}'=227
-']'=228
-')'=229
-';'=230
-'/'=231
-'_'=232
+'??'=222
+'%'=223
+'+'=224
+'?'=225
+'"'=226
+'\''=227
+'}'=228
+']'=229
+')'=230
+';'=231
+'/'=232
+'_'=233
diff --git a/posthog/hogql/grammar/HogQLParserVisitor.py b/posthog/hogql/grammar/HogQLParserVisitor.py
@@ -359,6 +359,11 @@ def visitColumnExprTimestamp(self, ctx:HogQLParser.ColumnExprTimestampContext):
         return self.visitChildren(ctx)
 
 
+    # Visit a parse tree produced by HogQLParser#ColumnExprNullish.
+    def visitColumnExprNullish(self, ctx:HogQLParser.ColumnExprNullishContext):
+        return self.visitChildren(ctx)
+
+
     # Visit a parse tree produced by HogQLParser#ColumnExprAnd.
     def visitColumnExprAnd(self, ctx:HogQLParser.ColumnExprAndContext):
         return self.visitChildren(ctx)

diff --git a/posthog/hogql/parser.py b/posthog/hogql/parser.py
@@ -759,3 +759,6 @@ def visitIdentifier(self, ctx: HogQLParser.IdentifierContext):
 
     def visitEnumValue(self, ctx: HogQLParser.EnumValueContext):
         raise NotImplementedException(f"Unsupported node: EnumValue")
+
+    def visitColumnExprNullish(self, ctx: HogQLParser.ColumnExprNullishContext):
+        return ast.Call(name="ifNull", args=[self.visit(ctx.columnExpr(0)), self.visit(ctx.columnExpr(1))])
diff --git a/posthog/hogql/test/test_query.py b/posthog/hogql/test/test_query.py
@@ -1143,3 +1143,26 @@ def test_null_equality(self):
             query = f"select a {op} {b} from (select {a} as a)"
             response = execute_hogql_query(query, team=self.team)
             self.assertEqual(response.results, [(res,)], query)
+
+    def test_nullish_coalescing(self):
+        query = """
+            SELECT
+                null ?? 1,
+                null ?? null ?? 2,
+                3 ?? null,
+                null ?? 'string',
+                1 + (null ?? 2) + 3,
+                1 + null ?? 2 + 3,
+                10 ?? true ? 20 : 30,
+                10 ?? 5 + 10
+        """
+
+        response = execute_hogql_query(
+            query,
+            team=self.team,
+        )
+
+        self.assertEqual(
+            response.results,
+            [(1, 2, 3, "string", 6, 5, 20, 10)],
+        )