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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Fix the OP_OpenEphemeral opcode in the bytecode engine so that if it is called a second or subsequent time, it merely clears the existing table rather than creating a new one. Proposed fix for ticket [d0866b26f83e9c55e30de0821f5d].
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SHA3-256: 4678cb1044f0b4dc813e48f3bd0f85240a66e2ecf8763280d66726cc031c93a7
User & Date: drh 2018-12-31 16:36:42
References
2019-06-26
20:00 New ticket [9cdc5c46] Incorrect result from second execution of correlated scalar sub-query that uses a partial sort. artifact: 1f188ca2 user: dan
2019-01-01
13:02 Open ticket [d0866b26]: Window function in correlated subquery causes assertion fault plus 4 other changes artifact: 55b13ed5 user: drh
Context
2018-12-31
17:58
Small changes to the OP_OpenEphemeral opcode to improve testability. check-in: f856676c user: drh tags: trunk
16:36
Fix the OP_OpenEphemeral opcode in the bytecode engine so that if it is called a second or subsequent time, it merely clears the existing table rather than creating a new one. Proposed fix for ticket [d0866b26f83e9c55e30de0821f5d]. check-in: 4678cb10 user: drh tags: trunk
2018-12-29
14:23
Additional small performance increase and size reduction to the sqlite3VdbeMakeLabel() mechanism. check-in: 1bdee199 user: drh tags: trunk
Changes
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Changes to src/vdbe.c.

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/* Opcode: OpenEphemeral P1 P2 * P4 P5
** Synopsis: nColumn=P2
**
** Open a new cursor P1 to a transient table.
** The cursor is always opened read/write even if 
** the main database is read-only.  The ephemeral
** table is deleted automatically when the cursor is closed.



**
** P2 is the number of columns in the ephemeral table.
** The cursor points to a BTree table if P4==0 and to a BTree index
** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
** that defines the format of keys in the index.
**
** The P5 parameter can be a mask of the BTREE_* flags defined
................................................................................
      SQLITE_OPEN_READWRITE |
      SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE |
      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;
  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );








  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->isEphemeral = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBtx, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
................................................................................
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling
    ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
    ** opening it. If a transient table is required, just use the
    ** automatically created table with root-page 1 (an BLOB_INTKEY table).
    */
    if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
      int pgno;
      assert( pOp->p4type==P4_KEYINFO );
      rc = sqlite3BtreeCreateTable(pCx->pBtx, &pgno, BTREE_BLOBKEY | pOp->p5); 

      if( rc==SQLITE_OK ){
        assert( pgno==MASTER_ROOT+1 );
        assert( pKeyInfo->db==db );
        assert( pKeyInfo->enc==ENC(db) );
        rc = sqlite3BtreeCursor(pCx->pBtx, pgno, BTREE_WRCSR,
                                pKeyInfo, pCx->uc.pCursor);
      }
      pCx->isTable = 0;
    }else{

      rc = sqlite3BtreeCursor(pCx->pBtx, MASTER_ROOT, BTREE_WRCSR,
                              0, pCx->uc.pCursor);
      pCx->isTable = 1;
    }
  }
  if( rc ) goto abort_due_to_error;
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);







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/* Opcode: OpenEphemeral P1 P2 * P4 P5
** Synopsis: nColumn=P2
**
** Open a new cursor P1 to a transient table.
** The cursor is always opened read/write even if 
** the main database is read-only.  The ephemeral
** table is deleted automatically when the cursor is closed.
**
** If the cursor P1 is already opened on an ephermal table, the table
** is cleared (all content is erased).
**
** P2 is the number of columns in the ephemeral table.
** The cursor points to a BTree table if P4==0 and to a BTree index
** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
** that defines the format of keys in the index.
**
** The P5 parameter can be a mask of the BTREE_* flags defined
................................................................................
      SQLITE_OPEN_READWRITE |
      SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE |
      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;
  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = p->apCsr[pOp->p1];
  if( pCx ){
    /* If the ephermeral table is already open, erase all existing content
    ** so that the table is empty again, rather than creating a new table. */
    rc = sqlite3BtreeClearTable(pCx->pBtx, pCx->pgnoRoot, 0);
    if( rc ) goto abort_due_to_error;
    break;
  }
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->isEphemeral = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBtx, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
................................................................................
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling
    ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
    ** opening it. If a transient table is required, just use the
    ** automatically created table with root-page 1 (an BLOB_INTKEY table).
    */
    if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){

      assert( pOp->p4type==P4_KEYINFO );
      rc = sqlite3BtreeCreateTable(pCx->pBtx, (int*)&pCx->pgnoRoot,
                                   BTREE_BLOBKEY | pOp->p5); 
      if( rc==SQLITE_OK ){
        assert( pCx->pgnoRoot==MASTER_ROOT+1 );
        assert( pKeyInfo->db==db );
        assert( pKeyInfo->enc==ENC(db) );
        rc = sqlite3BtreeCursor(pCx->pBtx, pCx->pgnoRoot, BTREE_WRCSR,
                                pKeyInfo, pCx->uc.pCursor);
      }
      pCx->isTable = 0;
    }else{
      pCx->pgnoRoot = MASTER_ROOT;
      rc = sqlite3BtreeCursor(pCx->pBtx, MASTER_ROOT, BTREE_WRCSR,
                              0, pCx->uc.pCursor);
      pCx->isTable = 1;
    }
  }
  if( rc ) goto abort_due_to_error;
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);

Changes to test/window1.test.

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  SELECT y, y+1, y+2 FROM (
    SELECT c IN (
      SELECT (row_number() OVER()) FROM t1
    ) AS y FROM t2
  );
} {1 2 3}














































finish_test







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  SELECT y, y+1, y+2 FROM (
    SELECT c IN (
      SELECT (row_number() OVER()) FROM t1
    ) AS y FROM t2
  );
} {1 2 3}

# 2018-12-31
# https://www.sqlite.org/src/info/d0866b26f83e9c55
# Window function in correlated subquery causes assertion fault 
#
do_catchsql_test 15.0 {
  WITH t(id, parent) AS (
  SELECT CAST(1 AS INT), CAST(NULL AS INT)
  UNION ALL
  SELECT 2, NULL
  UNION ALL
  SELECT 3, 1
  UNION ALL
  SELECT 4, 1
  UNION ALL
  SELECT 5, 2
  UNION ALL
  SELECT 6, 2
  ), q AS (
  SELECT t.*, ROW_NUMBER() OVER (ORDER BY t.id) AS rn
    FROM t
   WHERE parent IS NULL
   UNION ALL
  SELECT t.*, ROW_NUMBER() OVER (ORDER BY t.id) AS rn
    FROM q
    JOIN t
      ON t.parent = q.id
  )
  SELECT *
    FROM q;
} {1 {cannot use window functions in recursive queries}}
do_execsql_test 15.1 {
  DROP TABLE IF EXISTS t1;
  DROP TABLE IF EXISTS t2;
  CREATE TABLE t1(x);
  INSERT INTO t1 VALUES('a'), ('b'), ('c');
  CREATE TABLE t2(a, b);
  INSERT INTO t2 VALUES('X', 1), ('X', 2), ('Y', 2), ('Y', 3);
  SELECT x, (
    SELECT sum(b)
      OVER (PARTITION BY a ROWS BETWEEN UNBOUNDED PRECEDING
                                    AND UNBOUNDED FOLLOWING)
    FROM t2 WHERE b<x
  ) FROM t1;
} {a 3 b 3 c 3}

finish_test