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Overview
Comment:Improved comments on foreign key logic.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | omit-rowid
Files: files | file ages | folders
SHA1: 1315d9109c7105f4a62bb2d43ca6948d41245129
User & Date: drh 2013-11-03 02:27:58
Context
2013-11-04
13:56
Correctly handle self-referential foreign keys on WITHOUT ROWID tables. check-in: af128862 user: drh tags: omit-rowid
2013-11-03
02:27
Improved comments on foreign key logic. check-in: 1315d910 user: drh tags: omit-rowid
2013-11-02
22:29
Improved Synopsis on register comparison operators. Fix a bug on the constraint check generator. check-in: a7a18b65 user: drh tags: omit-rowid
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/build.c.

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}

/*
** This routine is called to create a new foreign key on the table
** currently under construction.  pFromCol determines which columns
** in the current table point to the foreign key.  If pFromCol==0 then
** connect the key to the last column inserted.  pTo is the name of
** the table referred to.  pToCol is a list of tables in the other
** pTo table that the foreign key points to.  flags contains all
** information about the conflict resolution algorithms specified
** in the ON DELETE, ON UPDATE and ON INSERT clauses.
**
** An FKey structure is created and added to the table currently
** under construction in the pParse->pNewTable field.
**
** The foreign key is set for IMMEDIATE processing.  A subsequent call







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}

/*
** This routine is called to create a new foreign key on the table
** currently under construction.  pFromCol determines which columns
** in the current table point to the foreign key.  If pFromCol==0 then
** connect the key to the last column inserted.  pTo is the name of
** the table referred to (a.k.a the "parent" table).  pToCol is a list
** of tables in the parent pTo table.  flags contains all
** information about the conflict resolution algorithms specified
** in the ON DELETE, ON UPDATE and ON INSERT clauses.
**
** An FKey structure is created and added to the table currently
** under construction in the pParse->pNewTable field.
**
** The foreign key is set for IMMEDIATE processing.  A subsequent call

Changes to src/fkey.c.

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**   INSERT      deferred    Decrement the "deferred constraint counter".
**
** These operations are identified in the comment at the top of this file 
** (fkey.c) as "I.2" and "D.2".
*/
static void fkScanChildren(
  Parse *pParse,                  /* Parse context */
  SrcList *pSrc,                  /* SrcList containing the table to scan */
  Table *pTab,
  Index *pIdx,                    /* Foreign key index */
  FKey *pFKey,                    /* Foreign key relationship */
  int *aiCol,                     /* Map from pIdx cols to child table cols */
  int regData,                    /* Referenced table data starts here */
  int nIncr                       /* Amount to increment deferred counter by */
){
  sqlite3 *db = pParse->db;       /* Database handle */
  int i;                          /* Iterator variable */
  Expr *pWhere = 0;               /* WHERE clause to scan with */
  NameContext sNameContext;       /* Context used to resolve WHERE clause */
  WhereInfo *pWInfo;              /* Context used by sqlite3WhereXXX() */
  int iFkIfZero = 0;              /* Address of OP_FkIfZero */
  Vdbe *v = sqlite3GetVdbe(pParse);

  assert( !pIdx || pIdx->pTable==pTab );



  if( nIncr<0 ){
    iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
  }

  /* Create an Expr object representing an SQL expression like:
  **
................................................................................
  }

  /* If the child table is the same as the parent table, and this scan
  ** is taking place as part of a DELETE operation (operation D.2), omit the
  ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE 
  ** clause, where $rowid is the rowid of the row being deleted.  */
  if( pTab==pFKey->pFrom && nIncr>0 && HasRowid(pTab) /*FIXME*/ ){
    Expr *pEq;                    /* Expression (pLeft = pRight) */
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */
    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
    pRight = sqlite3Expr(db, TK_COLUMN, 0);
    if( pLeft && pRight ){
      pLeft->iTable = regData;
      pLeft->affinity = SQLITE_AFF_INTEGER;
      pRight->iTable = pSrc->a[0].iCursor;
      pRight->iColumn = -1;
    }
    pEq = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
    pWhere = sqlite3ExprAnd(db, pWhere, pEq);
  }

  /* Resolve the references in the WHERE clause. */
  memset(&sNameContext, 0, sizeof(NameContext));
  sNameContext.pSrcList = pSrc;
  sNameContext.pParse = pParse;
  sqlite3ResolveExprNames(&sNameContext, pWhere);
................................................................................
  sqlite3ExprDelete(db, pWhere);
  if( iFkIfZero ){
    sqlite3VdbeJumpHere(v, iFkIfZero);
  }
}

/*
** This function returns a pointer to the head of a linked list of FK
** constraints for which table pTab is the parent table. For example,
** given the following schema:
**
**   CREATE TABLE t1(a PRIMARY KEY);
**   CREATE TABLE t2(b REFERENCES t1(a);
**
** Calling this function with table "t1" as an argument returns a pointer
** to the FKey structure representing the foreign key constraint on table
................................................................................
      ** be found, adding the child row has violated the FK constraint. */ 
      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1,isIgnore);
    }

    sqlite3DbFree(db, aiFree);
  }

  /* Loop through all the foreign key constraints that refer to this table */

  for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
    Index *pIdx = 0;              /* Foreign key index for pFKey */
    SrcList *pSrc;
    int *aiCol = 0;

    if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){
      continue;
................................................................................

    if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
      if( !isIgnoreErrors || db->mallocFailed ) return;
      continue;
    }
    assert( aiCol || pFKey->nCol==1 );

    /* Create a SrcList structure containing a single table (the table 
    ** the foreign key that refers to this table is attached to). This
    ** is required for the sqlite3WhereXXX() interface.  */
    pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
    if( pSrc ){
      struct SrcList_item *pItem = pSrc->a;
      pItem->pTab = pFKey->pFrom;
      pItem->zName = pFKey->pFrom->zName;
      pItem->pTab->nRef++;
      pItem->iCursor = pParse->nTab++;







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**   INSERT      deferred    Decrement the "deferred constraint counter".
**
** These operations are identified in the comment at the top of this file 
** (fkey.c) as "I.2" and "D.2".
*/
static void fkScanChildren(
  Parse *pParse,                  /* Parse context */
  SrcList *pSrc,                  /* The child table to be scanned */
  Table *pTab,                    /* The parent table */
  Index *pIdx,                    /* Index on parent covering the foreign key */
  FKey *pFKey,                    /* The foreign key linking pSrc to pTab */
  int *aiCol,                     /* Map from pIdx cols to child table cols */
  int regData,                    /* Parent row data starts here */
  int nIncr                       /* Amount to increment deferred counter by */
){
  sqlite3 *db = pParse->db;       /* Database handle */
  int i;                          /* Iterator variable */
  Expr *pWhere = 0;               /* WHERE clause to scan with */
  NameContext sNameContext;       /* Context used to resolve WHERE clause */
  WhereInfo *pWInfo;              /* Context used by sqlite3WhereXXX() */
  int iFkIfZero = 0;              /* Address of OP_FkIfZero */
  Vdbe *v = sqlite3GetVdbe(pParse);

  assert( pIdx==0 || pIdx->pTable==pTab );
  assert( pIdx==0 || pIdx->nKeyCol==pFKey->nCol );
  assert( pIdx!=0 || pFKey->nCol==1 );

  if( nIncr<0 ){
    iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
  }

  /* Create an Expr object representing an SQL expression like:
  **
................................................................................
  }

  /* If the child table is the same as the parent table, and this scan
  ** is taking place as part of a DELETE operation (operation D.2), omit the
  ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE 
  ** clause, where $rowid is the rowid of the row being deleted.  */
  if( pTab==pFKey->pFrom && nIncr>0 && HasRowid(pTab) /*FIXME*/ ){
    Expr *pNe;                    /* Expression (pLeft != pRight) */
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */
    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
    pRight = sqlite3Expr(db, TK_COLUMN, 0);
    if( pLeft && pRight ){
      pLeft->iTable = regData;
      pLeft->affinity = SQLITE_AFF_INTEGER;
      pRight->iTable = pSrc->a[0].iCursor;
      pRight->iColumn = -1;
    }
    pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
    pWhere = sqlite3ExprAnd(db, pWhere, pNe);
  }

  /* Resolve the references in the WHERE clause. */
  memset(&sNameContext, 0, sizeof(NameContext));
  sNameContext.pSrcList = pSrc;
  sNameContext.pParse = pParse;
  sqlite3ResolveExprNames(&sNameContext, pWhere);
................................................................................
  sqlite3ExprDelete(db, pWhere);
  if( iFkIfZero ){
    sqlite3VdbeJumpHere(v, iFkIfZero);
  }
}

/*
** This function returns a linked list of FKey objects (connected by
** FKey.pNextTo) holding all children of table pTab.  For example,
** given the following schema:
**
**   CREATE TABLE t1(a PRIMARY KEY);
**   CREATE TABLE t2(b REFERENCES t1(a);
**
** Calling this function with table "t1" as an argument returns a pointer
** to the FKey structure representing the foreign key constraint on table
................................................................................
      ** be found, adding the child row has violated the FK constraint. */ 
      fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1,isIgnore);
    }

    sqlite3DbFree(db, aiFree);
  }

  /* Loop through all the foreign key constraints that refer to this table.
  ** (the "child" constraints) */
  for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
    Index *pIdx = 0;              /* Foreign key index for pFKey */
    SrcList *pSrc;
    int *aiCol = 0;

    if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){
      continue;
................................................................................

    if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
      if( !isIgnoreErrors || db->mallocFailed ) return;
      continue;
    }
    assert( aiCol || pFKey->nCol==1 );

    /* Create a SrcList structure containing the child table.  We need the
    ** child table as a SrcList for sqlite3WhereBegin() */

    pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
    if( pSrc ){
      struct SrcList_item *pItem = pSrc->a;
      pItem->pTab = pFKey->pFrom;
      pItem->zName = pFKey->pFrom->zName;
      pItem->pTab->nRef++;
      pItem->iCursor = pParse->nTab++;

Changes to src/sqliteInt.h.

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**
**     CREATE TABLE ex1(
**       a INTEGER PRIMARY KEY,
**       b INTEGER CONSTRAINT fk1 REFERENCES ex2(x)
**     );
**
** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".




**
** Each REFERENCES clause generates an instance of the following structure
** which is attached to the from-table.  The to-table need not exist when
** the from-table is created.  The existence of the to-table is not checked.





*/
struct FKey {
  Table *pFrom;     /* Table containing the REFERENCES clause (aka: Child) */
  FKey *pNextFrom;  /* Next foreign key in pFrom */
  char *zTo;        /* Name of table that the key points to (aka: Parent) */
  FKey *pNextTo;    /* Next foreign key on table named zTo */
  FKey *pPrevTo;    /* Previous foreign key on table named zTo */
  int nCol;         /* Number of columns in this key */
  /* EV: R-30323-21917 */
  u8 isDeferred;    /* True if constraint checking is deferred till COMMIT */
  u8 aAction[2];          /* ON DELETE and ON UPDATE actions, respectively */
  Trigger *apTrigger[2];  /* Triggers for aAction[] actions */
  struct sColMap {  /* Mapping of columns in pFrom to columns in zTo */
    int iFrom;         /* Index of column in pFrom */
    char *zCol;        /* Name of column in zTo.  If 0 use PRIMARY KEY */
  } aCol[1];        /* One entry for each of nCol column s */
};

/*
** SQLite supports many different ways to resolve a constraint
** error.  ROLLBACK processing means that a constraint violation
** causes the operation in process to fail and for the current transaction
** to be rolled back.  ABORT processing means the operation in process







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**
**     CREATE TABLE ex1(
**       a INTEGER PRIMARY KEY,
**       b INTEGER CONSTRAINT fk1 REFERENCES ex2(x)
**     );
**
** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".
** Equivalent names:
**
**     from-table == child-table
**       to-table == parent-table
**
** Each REFERENCES clause generates an instance of the following structure
** which is attached to the from-table.  The to-table need not exist when
** the from-table is created.  The existence of the to-table is not checked.
**
** The list of all parents for child Table X is held at X.pFKey.
**
** A list of all children for a table named Z (which might not even exist)
** is held in Schema.fkeyHash with a hash key of Z.
*/
struct FKey {
  Table *pFrom;     /* Table containing the REFERENCES clause (aka: Child) */
  FKey *pNextFrom;  /* Next FKey with the same in pFrom. Next parent of pFrom */
  char *zTo;        /* Name of table that the key points to (aka: Parent) */
  FKey *pNextTo;    /* Next with the same zTo. Next child of zTo. */
  FKey *pPrevTo;    /* Previous with the same zTo */
  int nCol;         /* Number of columns in this key */
  /* EV: R-30323-21917 */
  u8 isDeferred;       /* True if constraint checking is deferred till COMMIT */
  u8 aAction[2];        /* ON DELETE and ON UPDATE actions, respectively */
  Trigger *apTrigger[2];/* Triggers for aAction[] actions */
  struct sColMap {      /* Mapping of columns in pFrom to columns in zTo */
    int iFrom;            /* Index of column in pFrom */
    char *zCol;           /* Name of column in zTo.  If NULL use PRIMARY KEY */
  } aCol[1];            /* One entry for each of nCol columns */
};

/*
** SQLite supports many different ways to resolve a constraint
** error.  ROLLBACK processing means that a constraint violation
** causes the operation in process to fail and for the current transaction
** to be rolled back.  ABORT processing means the operation in process