Support SKIP LOCKED and NOWAIT (#129)

* feat: updated syntax parser

* feat: added keywords and tests

* feat: updated to-sql

* fix: renamed interface

* feat: reverted keyword changes

* cleanup keywords.ts

* feat: cleanup eof in keywords.ts

* removed eol line

* reverting keywords.ts

Author: arajski

src/syntax/ast.ts

@@ -636,6 +636,7 @@ export interface SelectFromStatement extends PGNode {
     orderBy?: OrderByStatement[] | nil;
     distinct?: 'all' | 'distinct' | Expr[] | nil;
     for?: ForStatement;
+    skip?: SkipClause;
 }
 
 export interface SelectFromUnion extends PGNode {
@@ -654,6 +655,10 @@ export interface ForStatement extends PGNode {
     type: 'update' | 'no key update' | 'share' | 'key share';
 }
 
+export interface SkipClause extends PGNode {
+    type: 'nowait' | 'skip locked' 
+}
+
 export interface LimitStatement extends PGNode {
     limit?: Expr | nil;
     offset?: Expr | nil;

src/syntax/base.ne

@@ -240,6 +240,9 @@ kw_raise -> %word {% notReservedKw('raise')  %}
 kw_continue -> %word {% notReservedKw('continue')  %}
 kw_share -> %word {% notReservedKw('share')  %}
 kw_refresh -> %word {% notReservedKw('refresh')  %}
+kw_nowait -> %word {% notReservedKw('nowait')  %}
+kw_skip -> %word {% notReservedKw('skip')  %}
+kw_locked -> %word {% notReservedKw('locked')  %}
 
 
 # === Composite keywords

src/syntax/select.ne

@@ -10,14 +10,17 @@ array_of[EXP] -> $EXP (%comma $EXP {% last %}):* {% ([head, tail]) => {
 # https://www.postgresql.org/docs/12/sql-select.html
 
 select_statement
-    -> select_what select_from:? select_where:? (select_groupby select_having:?):? select_order_by:? select_limit_offset:? select_for:?
+    -> select_what select_from:? select_where:? (select_groupby select_having:?):? select_order_by:? select_limit_offset:? (select_for select_skip:?):?
     {% x => {
-        let [what, from, where, _groupBy, orderBy, limit, selectFor] = x;
+        let [what, from, where, _groupBy, orderBy, limit, _selectFor] = x;
         from = unwrap(from);
         let groupBy = _groupBy && _groupBy[0];
         let having = _groupBy && _groupBy[1];
         groupBy = groupBy && (groupBy.length === 1 && groupBy[0].type === 'list' ? groupBy[0].expressions : groupBy);
         having = having && unwrap(having);
+        let selectFor = _selectFor && _selectFor[0];
+        let skip = _selectFor && _selectFor[1];
+        skip = unwrap(skip);
         return track(x, {
             ...what,
             ...from ? { from: Array.isArray(from) ? from : [from] } : {},
@@ -27,6 +30,7 @@ select_statement
             ...orderBy ? { orderBy } : {},
             ...where ? { where } : {},
             ...selectFor ? { for: selectFor[1] } : {},
+            ...skip ? { skip } : {},
             type: 'select',
         });
     } %}
@@ -201,6 +205,9 @@ select_for -> %kw_for (
     | kw_share {% x => track(x, {type: 'share'}) %}
     | kw_key kw_share {% x => track(x, {type: 'key share'}) %})
 
+# [ NOWAIT | SKIP LOCKED ]
+select_skip -> (kw_nowait {% x => track(x, {type: 'nowait'}) %} | kw_skip kw_locked {% x => track(x, {type: 'skip locked'}) %})
+
 select_order_by -> (%kw_order kw_by) select_order_by_expr (comma select_order_by_expr {%last%}):*  {% ([_, head, tail]) => {
     return [head, ...(tail || [])];
 } %}

src/syntax/select.spec.ts

@@ -920,4 +920,27 @@ describe('Select statements', () => {
             type: 'key share',
         }
     });
+
+    checkSelect('select * from test for key share nowait', {
+        type: 'select',
+        from: [tbl('test')],
+        columns: columns({ type: 'ref', name: '*' }),
+        for: {
+            type: 'key share',
+        },
+        skip: {
+            type: 'nowait',
+        }
+    });
+    checkSelect('select * from test for key share skip locked', {
+        type: 'select',
+        from: [tbl('test')],
+        columns: columns({ type: 'ref', name: '*' }),
+        for: {
+            type: 'key share',
+        },
+        skip: {
+            type: 'skip locked',
+        }
+    });
 });

src/to-sql.ts

@@ -1356,6 +1356,9 @@ const visitor = astVisitor<IAstFullVisitor>(m => ({
 
         if (s.for) {
             ret.push('FOR ', s.for.type.toUpperCase());
+            if (s.skip) {
+                ret.push(' ', s.skip.type.toUpperCase());
+            }
         }
     },