SQLite

** The virtual table is currently read-only. And always returns zero rows.
** It is created with a single argument - the name of a Tcl command - as
** follows:
**
**   CREATE VIRTUAL TABLE x1 USING tcl(tcl_command);
**
** The command [tcl_command] is invoked when the table is first created (or
** connected), when the xBestIndex() method is invoked and when the xFilter()
** method is called. When it is created (or connected), it is invoked as
** follows:
**
**   tcl_command xConnect
**
** In this case the return value of the script is passed to the
** sqlite3_declare_vtab() function to create the virtual table schema.
**
** When the xBestIndex() method is called by SQLite, the Tcl command is

** populate the output fields of the sqlite3_index_info structure. Possible
** keys and the usage of the accompanying values are:
** 
**   "orderby"          (value of orderByConsumed flag)
**   "cost"             (value of estimatedCost field)
**   "rows"             (value of estimatedRows field)
**   "use"              (index of used constraint in aConstraint[])
**   "omit"             (like "use", but also sets omit flag)
**   "idxnum"           (value of idxNum field)
**   "idxstr"           (value of idxStr field)
**
** Refer to code below for further details.
**
** When SQLite calls the xFilter() method, this module invokes the following
** Tcl script:
**
**   tcl_command xFilter IDXNUM IDXSTR ARGLIST
**
** IDXNUM and IDXSTR are the values of the idxNum and idxStr parameters
** passed to xFilter. ARGLIST is a Tcl list containing each of the arguments
** passed to xFilter in text form.
**
** As with xBestIndex(), the return value of the script is interpreted as a
** list of key-value pairs. There is currently only one key defined - "sql".
** The value must be the full text of an SQL statement that returns the data
** for the current scan. The leftmost column returned by the SELECT is assumed
** to contain the rowid. Other columns must follow, in order from left to
** right.
*/


#include "sqliteInt.h"
#include "tcl.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE

typedef struct tcl_vtab tcl_vtab;
typedef struct tcl_cursor tcl_cursor;

/* 
** A fs virtual-table object 
*/
struct tcl_vtab {
  sqlite3_vtab base;
  Tcl_Interp *interp;
  Tcl_Obj *pCmd;
  sqlite3 *db;
};

/* A tcl cursor object */
struct tcl_cursor {
  sqlite3_vtab_cursor base;
  sqlite3_stmt *pStmt;            /* Read data from here */
};

/*
** This function is the implementation of both the xConnect and xCreate
** methods of the fs virtual table.
**
** The argv[] array contains the following:

  pTab = (tcl_vtab*)sqlite3_malloc(sizeof(tcl_vtab));
  if( pTab==0 ) return SQLITE_NOMEM;
  memset(pTab, 0, sizeof(tcl_vtab));

  pTab->pCmd = Tcl_NewStringObj(zCmd, -1);
  pTab->interp = interp;
  pTab->db = db;
  Tcl_IncrRefCount(pTab->pCmd);

  pScript = Tcl_DuplicateObj(pTab->pCmd);
  Tcl_IncrRefCount(pScript);
  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xConnect", -1));

  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);

}

/*
** Close a tcl cursor.
*/
static int tclClose(sqlite3_vtab_cursor *cur){
  tcl_cursor *pCur = (tcl_cursor *)cur;
  if( pCur ){
    sqlite3_finalize(pCur->pStmt);
    sqlite3_free(pCur);
  }
  return SQLITE_OK;
}

static int tclNext(sqlite3_vtab_cursor *pVtabCursor){
  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
  tcl_vtab *pTab = (tcl_vtab*)(pVtabCursor->pVtab);
  if( pCsr->pStmt ){
    tcl_vtab *pTab = (tcl_vtab*)(pVtabCursor->pVtab);
    int rc = sqlite3_step(pCsr->pStmt);
    if( rc!=SQLITE_ROW ){
      const char *zErr;
      rc = sqlite3_finalize(pCsr->pStmt);
      pCsr->pStmt = 0;
      if( rc!=SQLITE_OK ){
        zErr = sqlite3_errmsg(pTab->db);
        pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
      }
    }
  }
  return SQLITE_OK;
}

static int tclFilter(
  sqlite3_vtab_cursor *pVtabCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
  tcl_vtab *pTab = (tcl_vtab*)(pVtabCursor->pVtab);
  Tcl_Interp *interp = pTab->interp;
  Tcl_Obj *pScript;
  Tcl_Obj *pArg;
  int ii;
  int rc;

  pScript = Tcl_DuplicateObj(pTab->pCmd);
  Tcl_IncrRefCount(pScript);
  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("xFilter", -1));
  Tcl_ListObjAppendElement(interp, pScript, Tcl_NewIntObj(idxNum));
  if( idxStr ){
    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj(idxStr, -1));
  }else{
    Tcl_ListObjAppendElement(interp, pScript, Tcl_NewStringObj("", -1));
  }

  pArg = Tcl_NewObj();
  Tcl_IncrRefCount(pArg);
  for(ii=0; ii<argc; ii++){
    const char *zVal = (const char*)sqlite3_value_text(argv[ii]);
    Tcl_Obj *pVal;
    if( zVal==0 ){
      pVal = Tcl_NewObj();
    }else{
      pVal = Tcl_NewStringObj(zVal, -1);
    }
    Tcl_ListObjAppendElement(interp, pArg, pVal);
  }
  Tcl_ListObjAppendElement(interp, pScript, pArg);
  Tcl_DecrRefCount(pArg);

  rc = Tcl_EvalObjEx(interp, pScript, TCL_EVAL_GLOBAL);
  if( rc!=TCL_OK ){
    const char *zErr = Tcl_GetStringResult(interp);
    rc = SQLITE_ERROR;
    pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
  }else{
    /* Analyze the scripts return value. The return value should be a tcl 
    ** list object with an even number of elements. The first element of each
    ** pair must be one of:
    ** 
    **   "sql"          (SQL statement to return data)
    */
    Tcl_Obj *pRes = Tcl_GetObjResult(interp);
    Tcl_Obj **apElem = 0;
    int nElem;
    rc = Tcl_ListObjGetElements(interp, pRes, &nElem, &apElem);
    if( rc!=TCL_OK ){
      const char *zErr = Tcl_GetStringResult(interp);
      rc = SQLITE_ERROR;
      pTab->base.zErrMsg = sqlite3_mprintf("%s", zErr);
    }else{
      int iArgv = 1;
      for(ii=0; rc==SQLITE_OK && ii<nElem; ii+=2){
        const char *zCmd = Tcl_GetString(apElem[ii]);
        Tcl_Obj *p = apElem[ii+1];
        if( sqlite3_stricmp("sql", zCmd)==0 ){
          const char *zSql = Tcl_GetString(p);
          rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
          if( rc!=SQLITE_OK ){
            const char *zErr = sqlite3_errmsg(pTab->db);
            pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %s", zErr);
          }
        }else{
          rc = SQLITE_ERROR;
          pTab->base.zErrMsg = sqlite3_mprintf("unexpected: %s", zCmd);
        }
      }
    }
  }

  if( rc==SQLITE_OK ){
    rc = tclNext(pVtabCursor);
  }
  return rc;
}

static int tclColumn(
  sqlite3_vtab_cursor *pVtabCursor, 
  sqlite3_context *ctx, 
  int i
){
  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
  sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pStmt, i+1));
  return SQLITE_OK;
}

static int tclRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
  *pRowid = sqlite3_column_int64(pCsr->pStmt, 0);
  return SQLITE_OK;
}

static int tclEof(sqlite3_vtab_cursor *pVtabCursor){
  tcl_cursor *pCsr = (tcl_cursor*)pVtabCursor;
  return (pCsr->pStmt==0);
}

static int tclBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
  tcl_vtab *pTab = (tcl_vtab*)tab;
  Tcl_Interp *interp = pTab->interp;
  Tcl_Obj *pArg;
  Tcl_Obj *pScript;

do_eqp_test 1.2 {
  SELECT * FROM x1 WHERE a IN ('abc', 'def');
} {
  0 0 0 {SCAN TABLE x1 VIRTUAL TABLE INDEX 555:eq!}
  0 0 0 {EXECUTE LIST SUBQUERY 1}
}

#-------------------------------------------------------------------------
#
reset_db
register_tcl_module db

# Parameter $mode may be one of:
#
#   "omit" - Implement filtering. Set the omit flag.
#   "use"  - Implement filtering. Use the constraint, but do not set omit.
#   "use2" - Do not implement filtering. Use the constraint anyway.
#
#   
proc t1_vtab {mode method args} {
  switch -- $method {
    xConnect {
      return "CREATE TABLE t1(a, b)"
    }

    xBestIndex {
      set SQL_FILTER {SELECT * FROM t1x WHERE a='%1%'}
      set SQL_SCAN   {SELECT * FROM t1x}

      set clist [lindex $args 0]
      set idx 0
      for {set idx 0} {$idx < [llength $clist]} {incr idx} {
        array unset C
        array set C [lindex $clist $idx]
        if {$C(column)==0 && $C(op)=="eq" && $C(usable)} {
          switch -- $mode {
            "omit" {
              return [list omit $idx rows 10 cost 10 idxstr $SQL_FILTER]
            }
            "use" {
              return [list use $idx rows 10 cost 10 idxstr $SQL_FILTER]
            }
            "use2" {
              return [list use $idx rows 10 cost 10 idxstr $SQL_SCAN]
            }
            default {
              error "Bad mode - $mode"
            }
          }
        }
      }

      return [list idxstr {SELECT * FROM t1x}]
    }

    xFilter {
      set map [list %1% [lindex $args 2 0]]
      set sql [string map $map [lindex $args 1]]
      return [list sql $sql]
    }
  }

  return {}
}

do_execsql_test 2.1 {
  CREATE TABLE t1x(i INTEGER PRIMARY KEY, a, b);
  INSERT INTO t1x VALUES(1, 'one', 1);
  INSERT INTO t1x VALUES(2, 'two', 2);
  INSERT INTO t1x VALUES(3, 'three', 3);
  INSERT INTO t1x VALUES(4, 'four', 4);
}

foreach {tn mode} {
  1 use 2 omit 3 use2
} {
  do_execsql_test 2.2.$mode.1 "
    DROP TABLE IF EXISTS t1;
    CREATE VIRTUAL TABLE t1 USING tcl(t1_vtab $mode);
  "

  do_execsql_test 2.2.$mode.2 {SELECT * FROM t1} {one 1 two 2 three 3 four 4}
  do_execsql_test 2.2.$mode.3 {SELECT rowid FROM t1} {1 2 3 4}
  do_execsql_test 2.2.$mode.4 {SELECT rowid FROM t1 WHERE a='two'} {2} 

  do_execsql_test 2.2.$mode.5 {
    SELECT rowid FROM t1 WHERE a IN ('one', 'four') ORDER BY +rowid
  } {1 4} 

  set plan(use) {
    0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:SELECT * FROM t1x WHERE a='%1%'}
    0 0 0 {EXECUTE LIST SUBQUERY 1}
    0 0 0 {USE TEMP B-TREE FOR ORDER BY}
  }
  set plan(omit) {
    0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:SELECT * FROM t1x WHERE a='%1%'}
    0 0 0 {EXECUTE LIST SUBQUERY 1}
    0 0 0 {USE TEMP B-TREE FOR ORDER BY}
  }
  set plan(use2) {
    0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 0:SELECT * FROM t1x}
    0 0 0 {EXECUTE LIST SUBQUERY 1}
    0 0 0 {USE TEMP B-TREE FOR ORDER BY}
  }

  do_eqp_test 2.2.$mode.6 { 
    SELECT rowid FROM t1 WHERE a IN ('one', 'four') ORDER BY +rowid
  } $plan($mode)
}

finish_test