select.c

sqlite 嵌入式数据库的源码

/*
** 2001 September 15
**
** 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 contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.252 2005/06/12 21:35:52 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.
*/
Select *sqlite3SelectNew(
  ExprList *pEList,     /* which columns to include in the result */
  SrcList *pSrc,        /* the FROM clause -- which tables to scan */
  Expr *pWhere,         /* the WHERE clause */
  ExprList *pGroupBy,   /* the GROUP BY clause */
  Expr *pHaving,        /* the HAVING clause */
  ExprList *pOrderBy,   /* the ORDER BY clause */
  int isDistinct,       /* true if the DISTINCT keyword is present */
  Expr *pLimit,         /* LIMIT value.  NULL means not used */
  Expr *pOffset         /* OFFSET value.  NULL means no offset */
){
  Select *pNew;
  pNew = sqliteMalloc( sizeof(*pNew) );
  assert( !pOffset || pLimit );   /* Can't have OFFSET without LIMIT. */
  if( pNew==0 ){
    sqlite3ExprListDelete(pEList);
    sqlite3SrcListDelete(pSrc);
    sqlite3ExprDelete(pWhere);
    sqlite3ExprListDelete(pGroupBy);
    sqlite3ExprDelete(pHaving);
    sqlite3ExprListDelete(pOrderBy);
    sqlite3ExprDelete(pLimit);
    sqlite3ExprDelete(pOffset);
  }else{
    if( pEList==0 ){
      pEList = sqlite3ExprListAppend(0, sqlite3Expr(TK_ALL,0,0,0), 0);
    }
    pNew->pEList = pEList;
    pNew->pSrc = pSrc;
    pNew->pWhere = pWhere;
    pNew->pGroupBy = pGroupBy;
    pNew->pHaving = pHaving;
    pNew->pOrderBy = pOrderBy;
    pNew->isDistinct = isDistinct;
    pNew->op = TK_SELECT;
    pNew->pLimit = pLimit;
    pNew->pOffset = pOffset;
    pNew->iLimit = -1;
    pNew->iOffset = -1;
  }
  return pNew;
}

/*
** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
** type of join.  Return an integer constant that expresses that type
** in terms of the following bit values:
**
**     JT_INNER
**     JT_OUTER
**     JT_NATURAL
**     JT_LEFT
**     JT_RIGHT
**
** A full outer join is the combination of JT_LEFT and JT_RIGHT.
**
** If an illegal or unsupported join type is seen, then still return
** a join type, but put an error in the pParse structure.
*/
int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
  int jointype = 0;
  Token *apAll[3];
  Token *p;
  static const struct {
    const char *zKeyword;
    u8 nChar;
    u8 code;
  } keywords[] = {
    { "natural", 7, JT_NATURAL },
    { "left",    4, JT_LEFT|JT_OUTER },
    { "right",   5, JT_RIGHT|JT_OUTER },
    { "full",    4, JT_LEFT|JT_RIGHT|JT_OUTER },
    { "outer",   5, JT_OUTER },
    { "inner",   5, JT_INNER },
    { "cross",   5, JT_INNER },
  };
  int i, j;
  apAll[0] = pA;
  apAll[1] = pB;
  apAll[2] = pC;
  for(i=0; i<3 && apAll[i]; i++){
    p = apAll[i];
    for(j=0; j<sizeof(keywords)/sizeof(keywords[0]); j++){
      if( p->n==keywords[j].nChar 
          && sqlite3StrNICmp(p->z, keywords[j].zKeyword, p->n)==0 ){
        jointype |= keywords[j].code;
        break;
      }
    }
    if( j>=sizeof(keywords)/sizeof(keywords[0]) ){
      jointype |= JT_ERROR;
      break;
    }
  }
  if(
     (jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
     (jointype & JT_ERROR)!=0
  ){
    const char *zSp1 = " ";
    const char *zSp2 = " ";
    if( pB==0 ){ zSp1++; }
    if( pC==0 ){ zSp2++; }
    sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
       "%T%s%T%s%T", pA, zSp1, pB, zSp2, pC);
    jointype = JT_INNER;
  }else if( jointype & JT_RIGHT ){
    sqlite3ErrorMsg(pParse, 
      "RIGHT and FULL OUTER JOINs are not currently supported");
    jointype = JT_INNER;
  }
  return jointype;
}

/*
** Return the index of a column in a table.  Return -1 if the column
** is not contained in the table.
*/
static int columnIndex(Table *pTab, const char *zCol){
  int i;
  for(i=0; i<pTab->nCol; i++){
    if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
  }
  return -1;
}

/*
** Set the value of a token to a '\000'-terminated string.
*/
static void setToken(Token *p, const char *z){
  p->z = z;
  p->n = strlen(z);
  p->dyn = 0;
}


/*
** Add a term to the WHERE expression in *ppExpr that requires the
** zCol column to be equal in the two tables pTab1 and pTab2.
*/
static void addWhereTerm(
  const char *zCol,        /* Name of the column */
  const Table *pTab1,      /* First table */
  const char *zAlias1,     /* Alias for first table.  May be NULL */
  const Table *pTab2,      /* Second table */
  const char *zAlias2,     /* Alias for second table.  May be NULL */
  Expr **ppExpr            /* Add the equality term to this expression */
){
  Token dummy;
  Expr *pE1a, *pE1b, *pE1c;
  Expr *pE2a, *pE2b, *pE2c;
  Expr *pE;

  setToken(&dummy, zCol);
  pE1a = sqlite3Expr(TK_ID, 0, 0, &dummy);
  pE2a = sqlite3Expr(TK_ID, 0, 0, &dummy);
  if( zAlias1==0 ){
    zAlias1 = pTab1->zName;
  }
  setToken(&dummy, zAlias1);
  pE1b = sqlite3Expr(TK_ID, 0, 0, &dummy);
  if( zAlias2==0 ){
    zAlias2 = pTab2->zName;
  }
  setToken(&dummy, zAlias2);
  pE2b = sqlite3Expr(TK_ID, 0, 0, &dummy);
  pE1c = sqlite3Expr(TK_DOT, pE1b, pE1a, 0);
  pE2c = sqlite3Expr(TK_DOT, pE2b, pE2a, 0);
  pE = sqlite3Expr(TK_EQ, pE1c, pE2c, 0);
  ExprSetProperty(pE, EP_FromJoin);
  *ppExpr = sqlite3ExprAnd(*ppExpr, pE);
}

/*
** Set the EP_FromJoin property on all terms of the given expression.
**
** The EP_FromJoin property is used on terms of an expression to tell
** the LEFT OUTER JOIN processing logic that this term is part of the
** join restriction specified in the ON or USING clause and not a part
** of the more general WHERE clause.  These terms are moved over to the
** WHERE clause during join processing but we need to remember that they
** originated in the ON or USING clause.
*/
static void setJoinExpr(Expr *p){
  while( p ){
    ExprSetProperty(p, EP_FromJoin);
    setJoinExpr(p->pLeft);
    p = p->pRight;
  } 
}

/*
** This routine processes the join information for a SELECT statement.
** ON and USING clauses are converted into extra terms of the WHERE clause.
** NATURAL joins also create extra WHERE clause terms.
**
** The terms of a FROM clause are contained in the Select.pSrc structure.
** The left most table is the first entry in Select.pSrc.  The right-most
** table is the last entry.  The join operator is held in the entry to
** the left.  Thus entry 0 contains the join operator for the join between
** entries 0 and 1.  Any ON or USING clauses associated with the join are
** also attached to the left entry.
**
** This routine returns the number of errors encountered.
*/
static int sqliteProcessJoin(Parse *pParse, Select *p){
  SrcList *pSrc;                  /* All tables in the FROM clause */
  int i, j;                       /* Loop counters */
  struct SrcList_item *pLeft;     /* Left table being joined */
  struct SrcList_item *pRight;    /* Right table being joined */

  pSrc = p->pSrc;
  pLeft = &pSrc->a[0];
  pRight = &pLeft[1];
  for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
    Table *pLeftTab = pLeft->pTab;
    Table *pRightTab = pRight->pTab;

    if( pLeftTab==0 || pRightTab==0 ) continue;

    /* When the NATURAL keyword is present, add WHERE clause terms for
    ** every column that the two tables have in common.
    */
    if( pLeft->jointype & JT_NATURAL ){
      if( pLeft->pOn || pLeft->pUsing ){
        sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
           "an ON or USING clause", 0);
        return 1;
      }
      for(j=0; j<pLeftTab->nCol; j++){
        char *zName = pLeftTab->aCol[j].zName;
        if( columnIndex(pRightTab, zName)>=0 ){
          addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                              pRightTab, pRight->zAlias, &p->pWhere);
        }
      }
    }

    /* Disallow both ON and USING clauses in the same join
    */
    if( pLeft->pOn && pLeft->pUsing ){
      sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
        "clauses in the same join");
      return 1;
    }

    /* Add the ON clause to the end of the WHERE clause, connected by
    ** an AND operator.
    */
    if( pLeft->pOn ){
      setJoinExpr(pLeft->pOn);
      p->pWhere = sqlite3ExprAnd(p->pWhere, pLeft->pOn);
      pLeft->pOn = 0;
    }

    /* Create extra terms on the WHERE clause for each column named
    ** in the USING clause.  Example: If the two tables to be joined are 
    ** A and B and the USING clause names X, Y, and Z, then add this
    ** to the WHERE clause:    A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
    ** Report an error if any column mentioned in the USING clause is
    ** not contained in both tables to be joined.
    */
    if( pLeft->pUsing ){
      IdList *pList = pLeft->pUsing;
      for(j=0; j<pList->nId; j++){
        char *zName = pList->a[j].zName;
        if( columnIndex(pLeftTab, zName)<0 || columnIndex(pRightTab, zName)<0 ){
          sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
            "not present in both tables", zName);
          return 1;
        }
        addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                            pRightTab, pRight->zAlias, &p->pWhere);
      }
    }
  }
  return 0;
}

/*
** Delete the given Select structure and all of its substructures.
*/
void sqlite3SelectDelete(Select *p){
  if( p==0 ) return;
  sqlite3ExprListDelete(p->pEList);
  sqlite3SrcListDelete(p->pSrc);
  sqlite3ExprDelete(p->pWhere);
  sqlite3ExprListDelete(p->pGroupBy);
  sqlite3ExprDelete(p->pHaving);
  sqlite3ExprListDelete(p->pOrderBy);
  sqlite3SelectDelete(p->pPrior);
  sqlite3ExprDelete(p->pLimit);
  sqlite3ExprDelete(p->pOffset);
  sqliteFree(p);
}

/*
** Insert code into "v" that will push the record on the top of the
** stack into the sorter.
*/
static void pushOntoSorter(Parse *pParse, Vdbe *v, ExprList *pOrderBy){
  int i;
  for(i=0; i<pOrderBy->nExpr; i++){
    sqlite3ExprCode(pParse, pOrderBy->a[i].pExpr);
  }
  sqlite3VdbeAddOp(v, OP_MakeRecord, pOrderBy->nExpr, 0);
  sqlite3VdbeAddOp(v, OP_SortInsert, 0, 0);
}

/*
** Add code to implement the OFFSET and LIMIT
*/
static void codeLimiter(
  Vdbe *v,          /* Generate code into this VM */
  Select *p,        /* The SELECT statement being coded */
  int iContinue,    /* Jump here to skip the current record */
  int iBreak,       /* Jump here to end the loop */
  int nPop          /* Number of times to pop stack when jumping */
){
  if( p->iOffset>=0 ){
    int addr = sqlite3VdbeCurrentAddr(v) + 3;
    if( nPop>0 ) addr++;
    sqlite3VdbeAddOp(v, OP_MemIncr, p->iOffset, 0);
    sqlite3VdbeAddOp(v, OP_IfMemPos, p->iOffset, addr);
    if( nPop>0 ){
      sqlite3VdbeAddOp(v, OP_Pop, nPop, 0);
    }
    sqlite3VdbeAddOp(v, OP_Goto, 0, iContinue);
    VdbeComment((v, "# skip OFFSET records"));
  }
  if( p->iLimit>=0 ){
    sqlite3VdbeAddOp(v, OP_MemIncr, p->iLimit, iBreak);
    VdbeComment((v, "# exit when LIMIT reached"));
  }
}

/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**
** If srcTab and nColumn are both zero, then the pEList expressions
** are evaluated in order to get the data for this row.  If nColumn>0
** then data is pulled from srcTab and pEList is used only to get the
** datatypes for each column.
*/
static int selectInnerLoop(
  Parse *pParse,          /* The parser context */
  Select *p,              /* The complete select statement being coded */
  ExprList *pEList,       /* List of values being extracted */
  int srcTab,             /* Pull data from this table */
  int nColumn,            /* Number of columns in the source table */
  ExprList *pOrderBy,     /* If not NULL, sort results using this key */
  int distinct,           /* If >=0, make sure results are distinct */
  int eDest,              /* How to dispose of the results */
  int iParm,              /* An argument to the disposal method */
  int iContinue,          /* Jump here to continue with next row */
  int iBreak,             /* Jump here to break out of the inner loop */
  char *aff               /* affinity string if eDest is SRT_Union */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */

  if( v==0 ) return 0;
  assert( pEList!=0 );

  /* If there was a LIMIT clause on the SELECT statement, then do the check
  ** to see if this row should be output.
  */
  hasDistinct = distinct>=0 && pEList && pEList->nExpr>0;
  if( pOrderBy==0 && !hasDistinct ){
    codeLimiter(v, p, iContinue, iBreak, 0);
  }