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Add CREATE RECURSIVE VIEW syntax
This is specified in the SQL standard. The CREATE RECURSIVE VIEW specification is transformed into a normal CREATE VIEW statement with a WITH RECURSIVE clause. reviewed by Abhijit Menon-Sen and Stephen Frost
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@ -21,7 +21,7 @@ PostgreSQL documentation
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<refsynopsisdiv>
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<synopsis>
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CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW <replaceable class="PARAMETER">name</replaceable> [ ( <replaceable class="PARAMETER">column_name</replaceable> [, ...] ) ]
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CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW <replaceable class="PARAMETER">name</replaceable> [ ( <replaceable class="PARAMETER">column_name</replaceable> [, ...] ) ]
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[ WITH ( <replaceable class="PARAMETER">view_option_name</replaceable> [= <replaceable class="PARAMETER">view_option_value</replaceable>] [, ... ] ) ]
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AS <replaceable class="PARAMETER">query</replaceable>
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</synopsis>
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@ -80,6 +80,23 @@ CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW <replaceable class="PARAMETER">n
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>RECURSIVE</></term>
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<listitem>
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<para>
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Creates a recursive view. The syntax
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<synopsis>
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CREATE RECURSIVE VIEW <replaceable>name</> (<replaceable>columns</>) AS SELECT <replaceable>...</>;
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</synopsis>
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is equivalent to
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<synopsis>
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CREATE VIEW <replaceable>name</> AS WITH RECURSIVE <replaceable>name</> (<replaceable>columns</>) AS (SELECT <replaceable>...</>) SELECT <replaceable>columns</> FROM <replaceable>name</>;
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</synopsis>
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A view column list must be specified for a recursive view.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">name</replaceable></term>
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<listitem>
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@ -282,6 +299,16 @@ CREATE VIEW comedies AS
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<literal>*</> was used to create the view, columns added later to
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the table will not be part of the view.
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</para>
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<para>
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Create a recursive view consisting of the numbers from 1 to 100:
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<programlisting>
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CREATE RECURSIVE VIEW nums_1_100 (n) AS
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VALUES (1)
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UNION ALL
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SELECT n+1 FROM nums_1_100 WHERE n < 100;
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</programlisting>
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</para>
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</refsect1>
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<refsect1>
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@ -164,6 +164,7 @@ static void SplitColQualList(List *qualList,
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static void processCASbits(int cas_bits, int location, const char *constrType,
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bool *deferrable, bool *initdeferred, bool *not_valid,
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bool *no_inherit, core_yyscan_t yyscanner);
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static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
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%}
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@ -7839,6 +7840,30 @@ ViewStmt: CREATE OptTemp VIEW qualified_name opt_column_list opt_reloptions
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n->options = $8;
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$$ = (Node *) n;
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}
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| CREATE OptTemp RECURSIVE VIEW qualified_name '(' columnList ')' opt_reloptions
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AS SelectStmt
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{
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ViewStmt *n = makeNode(ViewStmt);
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n->view = $5;
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n->view->relpersistence = $2;
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n->aliases = $7;
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n->query = makeRecursiveViewSelect(n->view->relname, n->aliases, $11);
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n->replace = false;
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n->options = $9;
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$$ = (Node *) n;
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}
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| CREATE OR REPLACE OptTemp RECURSIVE VIEW qualified_name '(' columnList ')' opt_reloptions
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AS SelectStmt
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{
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ViewStmt *n = makeNode(ViewStmt);
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n->view = $7;
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n->view->relpersistence = $4;
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n->aliases = $9;
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n->query = makeRecursiveViewSelect(n->view->relname, n->aliases, $13);
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n->replace = true;
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n->options = $11;
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$$ = (Node *) n;
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}
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;
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opt_check_option:
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@ -13570,6 +13595,66 @@ processCASbits(int cas_bits, int location, const char *constrType,
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}
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}
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/*----------
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* Recursive view transformation
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*
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* Convert
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*
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* CREATE RECURSIVE VIEW relname (aliases) AS query
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*
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* to
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*
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* CREATE VIEW relname (aliases) AS
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* WITH RECURSIVE relname (aliases) AS (query)
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* SELECT aliases FROM relname
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*
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* Actually, just the WITH ... part, which is then inserted into the original
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* view definition as the query.
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* ----------
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*/
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static Node *
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makeRecursiveViewSelect(char *relname, List *aliases, Node *query)
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{
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SelectStmt *s = makeNode(SelectStmt);
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WithClause *w = makeNode(WithClause);
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CommonTableExpr *cte = makeNode(CommonTableExpr);
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List *tl = NIL;
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ListCell *lc;
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/* create common table expression */
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cte->ctename = relname;
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cte->aliascolnames = aliases;
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cte->ctequery = query;
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cte->location = -1;
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/* create WITH clause and attach CTE */
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w->recursive = true;
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w->ctes = list_make1(cte);
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w->location = -1;
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/* create target list for the new SELECT from the alias list of the
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* recursive view specification */
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foreach (lc, aliases)
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{
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ResTarget *rt = makeNode(ResTarget);
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rt->name = NULL;
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rt->indirection = NIL;
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rt->val = makeColumnRef(strVal(lfirst(lc)), NIL, -1, 0);
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rt->location = -1;
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tl = lappend(tl, rt);
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}
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/* create new SELECT combining WITH clause, target list, and fake FROM
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* clause */
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s->withClause = w;
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s->targetList = tl;
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s->fromClause = list_make1(makeRangeVar(NULL, relname, -1));
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return (Node *) s;
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}
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/* parser_init()
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* Initialize to parse one query string
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*/
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@ -49,6 +49,36 @@ SELECT * FROM t;
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5
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(5 rows)
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-- recursive view
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CREATE RECURSIVE VIEW nums (n) AS
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VALUES (1)
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UNION ALL
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SELECT n+1 FROM nums WHERE n < 5;
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SELECT * FROM nums;
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n
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---
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1
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2
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3
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4
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5
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(5 rows)
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CREATE OR REPLACE RECURSIVE VIEW nums (n) AS
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VALUES (1)
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UNION ALL
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SELECT n+1 FROM nums WHERE n < 6;
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SELECT * FROM nums;
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n
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---
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1
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2
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3
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4
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5
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6
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(6 rows)
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-- This is an infinite loop with UNION ALL, but not with UNION
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WITH RECURSIVE t(n) AS (
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SELECT 1
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@ -31,6 +31,21 @@ UNION ALL
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)
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SELECT * FROM t;
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-- recursive view
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CREATE RECURSIVE VIEW nums (n) AS
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VALUES (1)
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UNION ALL
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SELECT n+1 FROM nums WHERE n < 5;
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SELECT * FROM nums;
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CREATE OR REPLACE RECURSIVE VIEW nums (n) AS
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VALUES (1)
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UNION ALL
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SELECT n+1 FROM nums WHERE n < 6;
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SELECT * FROM nums;
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-- This is an infinite loop with UNION ALL, but not with UNION
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WITH RECURSIVE t(n) AS (
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SELECT 1
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