SQLite

  **       INSERT INTO <table1> SELECT * FROM <table2>;
  **
  ** Then special optimizations can be applied that make the transfer
  ** very fast and which reduce fragmentation of indices.
  **
  ** This is the 2nd template.
  */
  if( pColumn==0 
   && pSelect!=0
   && pTrigger==0
   && xferOptimization(pParse, pTab, pSelect, onError, iDb)
  ){
    assert( !pTrigger );
    assert( pList==0 );
    goto insert_end;
  }
#endif /* SQLITE_OMIT_XFER_OPT */

  /* If this is an AUTOINCREMENT table, look up the sequence number in the

  int emptyDestTest = 0;           /* Address of test for empty pDest */
  int emptySrcTest = 0;            /* Address of test for empty pSrc */
  Vdbe *v;                         /* The VDBE we are building */
  int regAutoinc;                  /* Memory register used by AUTOINC */
  int destHasUniqueIdx = 0;        /* True if pDest has a UNIQUE index */
  int regData, regRowid;           /* Registers holding data and rowid */

  assert( pSelect!=0 );


  if( pParse->pWith || pSelect->pWith ){
    /* Do not attempt to process this query if there are an WITH clauses
    ** attached to it. Proceeding may generate a false "no such table: xxx"
    ** error if pSelect reads from a CTE named "xxx".  */
    return 0;
  }



#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pDest) ){
    return 0;   /* tab1 must not be a virtual table */
  }
#endif
  if( onError==OE_Default ){
    if( pDest->iPKey>=0 ) onError = pDest->keyConf;

# 2007 January 24
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the INSERT transfer optimization.
#


set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix insert4

ifcapable !view||!subquery {
  finish_test

do_test 10.3 {
  execsql { PRAGMA integrity_check }
  set sqlite3_xferopt_count 0
  execsql { INSERT INTO x     SELECT * FROM t8 }
  set sqlite3_xferopt_count
} {1}

do_test 10.4 {
  execsql { PRAGMA integrity_check }
  set sqlite3_xferopt_count 0
  execsql { INSERT INTO x     SELECT * FROM t8  RETURNING * }
  set sqlite3_xferopt_count
} {0}

#-------------------------------------------------------------------------
# xfer transfer between tables where the source has an empty partial index.
#
do_execsql_test 11.0 {
  CREATE TABLE t9(a, b, c);
  CREATE INDEX t9a ON t9(a);

} {5.0 real}
do_execsql_test 15.1 {
  UPDATE t1 SET x=x+1 RETURNING x, affinity(x);
} {6.0 real}
do_execsql_test 15.2 {
  DELETE FROM t1 RETURNING x, affinity(x);
} {6.0 real}

# 2022-02-28 Forum post https://sqlite.org/forum/forumpost/595e132f71
# RETURNING with the xfer optimization
#
reset_db
do_execsql_test 16.0 {
  CREATE TABLE t1(a,b,c);
  INSERT INTO t1 VALUES(1,2,3),('a','b','c');
  CREATE TEMP TABLE t2(x,y,z);
  INSERT INTO t2 SELECT * FROM t1 RETURNING *;
} {1 2 3 a b c}
do_execsql_test 16.1 {
  SELECT * FROM t2;
} {1 2 3 a b c}

finish_test