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GeezerVison is showing github.com — sqlcipher/src/fkey.c at master · magic-coder/sqlcipher Expand file tree/ Copy pathfkey.cMore file actions 1421 lines (1322 loc) · 55.5 KB / Copy pathfkey.cFile metadata and controls1421 lines (1322 loc) · 55.5 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 /* ** ** 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 code used by the compiler to add foreign key ** support to compiled SQL statements. */ #include "sqliteInt.h" #ifndef SQLITE_OMIT_FOREIGN_KEY #ifndef SQLITE_OMIT_TRIGGER /* ** Deferred and Immediate FKs ** -------------------------- ** ** Foreign keys in SQLite come in two flavours: deferred and immediate. ** If an immediate foreign key constraint is violated, ** SQLITE_CONSTRAINT_FOREIGNKEY is returned and the current ** statement transaction rolled back. If a ** deferred foreign key constraint is violated, no action is taken ** immediately. However if the application attempts to commit the ** transaction before fixing the constraint violation, the attempt fails. ** ** Deferred constraints are implemented using a simple counter associated ** with the database handle. The counter is set to zero each time a ** database transaction is opened. Each time a statement is executed ** that causes a foreign key violation, the counter is incremented. Each ** time a statement is executed that removes an existing violation from ** the database, the counter is decremented. When the transaction is ** committed, the commit fails if the current value of the counter is ** greater than zero. This scheme has two big drawbacks: ** ** * When a commit fails due to a deferred foreign key constraint, ** there is no way to tell which foreign constraint is not satisfied, ** or which row it is not satisfied for. ** ** * If the database contains foreign key violations when the ** transaction is opened, this may cause the mechanism to malfunction. ** ** Despite these problems, this approach is adopted as it seems simpler ** than the alternatives. ** ** INSERT operations: ** ** I.1) For each FK for which the table is the child table, search ** the parent table for a match. If none is found increment the ** constraint counter. ** ** I.2) For each FK for which the table is the parent table, ** search the child table for rows that correspond to the new ** row in the parent table. Decrement the counter for each row ** found (as the constraint is now satisfied). ** ** DELETE operations: ** ** D.1) For each FK for which the table is the child table, ** search the parent table for a row that corresponds to the ** deleted row in the child table. If such a row is not found, ** decrement the counter. ** ** D.2) For each FK for which the table is the parent table, search ** the child table for rows that correspond to the deleted row ** in the parent table. For each found increment the counter. ** ** UPDATE operations: ** ** An UPDATE command requires that all 4 steps above are taken, but only ** for FK constraints for which the affected columns are actually ** modified (values must be compared at runtime). ** ** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2. ** This simplifies the implementation a bit. ** ** For the purposes of immediate FK constraints, the OR REPLACE conflict ** resolution is considered to delete rows before the new row is inserted. ** If a delete caused by OR REPLACE violates an FK constraint, an exception ** is thrown, even if the FK constraint would be satisfied after the new ** row is inserted. ** ** Immediate constraints are usually handled similarly. The only difference ** is that the counter used is stored as part of each individual statement ** object (struct Vdbe). If, after the statement has run, its immediate ** constraint counter is greater than zero, ** it returns SQLITE_CONSTRAINT_FOREIGNKEY ** and the statement transaction is rolled back. An exception is an INSERT ** statement that inserts a single row only (no triggers). In this case, ** instead of using a counter, an exception is thrown immediately if the ** INSERT violates a foreign key constraint. This is necessary as such ** an INSERT does not open a statement transaction. ** ** TODO: How should dropping a table be handled? How should renaming a ** table be handled? ** ** ** Query API Notes ** --------------- ** ** Before coding an UPDATE or DELETE row operation, the code-generator ** for those two operations needs to know whether or not the operation ** requires any FK processing and, if so, which columns of the original ** row are required by the FK processing VDBE code (i.e. if FKs were ** implemented using triggers, which of the old.* columns would be ** accessed). No information is required by the code-generator before ** coding an INSERT operation. The functions used by the UPDATE/DELETE ** generation code to query for this information are: ** ** sqlite3FkRequired() - Test to see if FK processing is required. ** sqlite3FkOldmask() - Query for the set of required old.* columns. ** ** ** Externally accessible module functions ** -------------------------------------- ** ** sqlite3FkCheck() - Check for foreign key violations. ** sqlite3FkActions() - Code triggers for ON UPDATE/ON DELETE actions. ** sqlite3FkDelete() - Delete an FKey structure. */ /* ** VDBE Calling Convention ** ----------------------- ** ** Example: ** ** For the following INSERT statement: ** ** CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c); ** INSERT INTO t1 VALUES(1, 2, 3.1); ** ** Register (x): 2 (type integer) ** Register (x+1): 1 (type integer) ** Register (x+2): NULL (type NULL) ** Register (x+3): 3.1 (type real) */ /* ** A foreign key constraint requires that the key columns in the parent ** table are collectively subject to a UNIQUE or PRIMARY KEY constraint. ** Given that pParent is the parent table for foreign key constraint pFKey, ** search the schema for a unique index on the parent key columns. ** ** If successful, zero is returned. If the parent key is an INTEGER PRIMARY ** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx ** is set to point to the unique index. ** ** If the parent key consists of a single column (the foreign key constraint ** is not a composite foreign key), output variable *paiCol is set to NULL. ** Otherwise, it is set to point to an allocated array of size N, where ** N is the number of columns in the parent key. The first element of the ** array is the index of the child table column that is mapped by the FK ** constraint to the parent table column stored in the left-most column ** of index *ppIdx. The second element of the array is the index of the ** child table column that corresponds to the second left-most column of ** *ppIdx, and so on. ** ** If the required index cannot be found, either because: ** ** 1) The named parent key columns do not exist, or ** ** 2) The named parent key columns do exist, but are not subject to a ** UNIQUE or PRIMARY KEY constraint, or ** ** 3) No parent key columns were provided explicitly as part of the ** foreign key definition, and the parent table does not have a ** PRIMARY KEY, or ** ** 4) No parent key columns were provided explicitly as part of the ** foreign key definition, and the PRIMARY KEY of the parent table ** consists of a different number of columns to the child key in ** the child table. ** ** then non-zero is returned, and a "foreign key mismatch" error loaded ** into pParse. If an OOM error occurs, non-zero is returned and the ** pParse->db->mallocFailed flag is set. */ int sqlite3FkLocateIndex( Parse *pParse, /* Parse context to store any error in */ Table *pParent, /* Parent table of FK constraint pFKey */ FKey *pFKey, /* Foreign key to find index for */ Index **ppIdx, /* OUT: Unique index on parent table */ int **paiCol /* OUT: Map of index columns in pFKey */ ){ Index *pIdx = 0; /* Value to return via *ppIdx */ int *aiCol = 0; /* Value to return via *paiCol */ int nCol = pFKey->nCol; /* Number of columns in parent key */ char *zKey = pFKey->aCol[0].zCol; /* Name of left-most parent key column */ /* The caller is responsible for zeroing output parameters. */ assert( ppIdx && *ppIdx==0 ); assert( !paiCol || *paiCol==0 ); assert( pParse ); /* If this is a non-composite (single column) foreign key, check if it ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx ** and *paiCol set to zero and return early. ** ** Otherwise, for a composite foreign key (more than one column), allocate ** space for the aiCol array (returned via output parameter *paiCol). ** Non-composite foreign keys do not require the aiCol array. */ if( nCol==1 ){ /* The FK maps to the IPK if any of the following are true: ** ** 1) There is an INTEGER PRIMARY KEY column and the FK is implicitly ** mapped to the primary key of table pParent, or ** 2) The FK is explicitly mapped to a column declared as INTEGER ** PRIMARY KEY. */ if( pParent->iPKey>=0 ){ if( !zKey ) return 0; if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zName, zKey) ) return 0; } }else if( paiCol ){ assert( nCol>1 ); aiCol = (int *)sqlite3DbMallocRawNN(pParse->db, nCol*sizeof(int)); if( !aiCol ) return 1; *paiCol = aiCol; } for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){ if( pIdx->nKeyCol==nCol && IsUniqueIndex(pIdx) && pIdx->pPartIdxWhere==0 ){ /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number ** of columns. If each indexed column corresponds to a foreign key ** column of pFKey, then this index is a winner. */ if( zKey==0 ){ /* If zKey is NULL, then this foreign key is implicitly mapped to ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be ** identified by the test. */ if( IsPrimaryKeyIndex(pIdx) ){ if( aiCol ){ int i; for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom; } break; } }else{ /* If zKey is non-NULL, then this foreign key was declared to ** map to an explicit list of columns in table pParent. Check if this ** index matches those columns. Also, check that the index uses ** the default collation sequences for each column. */ int i, j; for(i=0; i<nCol; i++){ i16 iCol = pIdx->aiColumn[i]; /* Index of column in parent tbl */ const char *zDfltColl; /* Def. collation for column */ char *zIdxCol; /* Name of indexed column */ if( iCol<0 ) break; /* No foreign keys against expression indexes */ /* If the index uses a collation sequence that is different from ** the default collation sequence for the column, this index is ** unusable. Bail out early in this case. */ zDfltColl = pParent->aCol[iCol].zColl; if( !zDfltColl ) zDfltColl = sqlite3StrBINARY; if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break; zIdxCol = pParent->aCol[iCol].zName; for(j=0; j<nCol; j++){ if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){ if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom; break; } } if( j==nCol ) break; } if( i==nCol ) break; /* pIdx is usable */ } } } if( !pIdx ){ if( !pParse->disableTriggers ){ sqlite3ErrorMsg(pParse, "foreign key mismatch - \"%w\" referencing \"%w\"", pFKey->pFrom->zName, pFKey->zTo); } sqlite3DbFree(pParse->db, aiCol); return 1; } *ppIdx = pIdx; return 0; } /* ** This function is called when a row is inserted into or deleted from the ** child table of foreign key constraint pFKey. If an SQL UPDATE is executed ** on the child table of pFKey, this function is invoked twice for each row ** affected - once to "delete" the old row, and then again to "insert" the ** new row. ** ** Each time it is called, this function generates VDBE code to locate the ** row in the parent table that corresponds to the row being inserted into ** or deleted from the child table. If the parent row can be found, no ** special action is taken. Otherwise, if the parent row can *not* be ** found in the parent table: ** ** Operation | FK type | Action taken ** -------------------------------------------------------------------------- ** INSERT immediate Increment the "immediate constraint counter". ** ** DELETE immediate Decrement the "immediate constraint counter". ** ** INSERT deferred Increment the "deferred constraint counter". ** ** DELETE deferred Decrement the "deferred constraint counter". ** ** These operations are identified in the comment at the top of this file ** (fkey.c) as "I.1" and "D.1". */ static void fkLookupParent( Parse *pParse, /* Parse context */ int iDb, /* Index of database housing pTab */ Table *pTab, /* Parent table of FK pFKey */ Index *pIdx, /* Unique index on parent key columns in pTab */ FKey *pFKey, /* Foreign key constraint */ int *aiCol, /* Map from parent key columns to child table columns */ int regData, /* Address of array containing child table row */ int nIncr, /* Increment constraint counter by this */ int isIgnore /* If true, pretend pTab contains all NULL values */ ){ int i; /* Iterator variable */ Vdbe *v = sqlite3GetVdbe(pParse); /* Vdbe to add code to */ int iCur = pParse->nTab - 1; /* Cursor number to use */ int iOk = sqlite3VdbeMakeLabel(v); /* jump here if parent key found */ /* If nIncr is less than zero, then check at runtime if there are any ** outstanding constraints to resolve. If there are not, there is no need ** to check if deleting this row resolves any outstanding violations. ** ** Check if any of the key columns in the child table row are NULL. If ** any are, then the constraint is considered satisfied. No need to ** search for a matching row in the parent table. */ if( nIncr<0 ){ sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk); VdbeCoverage(v); } for(i=0; i<pFKey->nCol; i++){ int iReg = aiCol[i] + regData + 1; sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); VdbeCoverage(v); } if( isIgnore==0 ){ if( pIdx==0 ){ /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY ** column of the parent table (table pTab). */ int iMustBeInt; /* Address of MustBeInt instruction */ int regTemp = sqlite3GetTempReg(pParse); /* Invoke MustBeInt to coerce the child key value to an integer (i.e. ** apply the affinity of the parent key). If this fails, then there ** is no matching parent key. Before using MustBeInt, make a copy of ** the value. Otherwise, the value inserted into the child key column ** will have INTEGER affinity applied to it, which may not be correct. */ sqlite3VdbeAddOp2(v, OP_SCopy, aiCol[0]+1+regData, regTemp); iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0); VdbeCoverage(v); /* If the parent table is the same as the child table, and we are about ** to increment the constraint-counter (i.e. this is an INSERT operation), ** then check if the row being inserted matches itself. If so, do not ** increment the constraint-counter. */ if( pTab==pFKey->pFrom && nIncr==1 ){ sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp); VdbeCoverage(v); sqlite3VdbeChangeP5(v, SQLITE_NOTNULL); } sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead); sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); VdbeCoverage(v); sqlite3VdbeGoto(v, iOk); sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2); sqlite3VdbeJumpHere(v, iMustBeInt); sqlite3ReleaseTempReg(pParse, regTemp); }else{ int nCol = pFKey->nCol; int regTemp = sqlite3GetTempRange(pParse, nCol); int regRec = sqlite3GetTempReg(pParse); sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb); sqlite3VdbeSetP4KeyInfo(pParse, pIdx); for(i=0; i<nCol; i++){ sqlite3VdbeAddOp2(v, OP_Copy, aiCol[i]+1+regData, regTemp+i); } /* If the parent table is the same as the child table, and we are about ** to increment the constraint-counter (i.e. this is an INSERT operation), ** then check if the row being inserted matches itself. If so, do not ** increment the constraint-counter. ** ** If any of the parent-key values are NULL, then the row cannot match ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any ** of the parent-key values are NULL (at this point it is known that ** none of the child key values are). */ if( pTab==pFKey->pFrom && nIncr==1 ){ int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1; for(i=0; i<nCol; i++){ int iChild = aiCol[i]+1+regData; int iParent = pIdx->aiColumn[i]+1+regData; assert( pIdx->aiColumn[i]>=0 ); assert( aiCol[i]!=pTab->iPKey ); if( pIdx->aiColumn[i]==pTab->iPKey ){ /* The parent key is a composite key that includes the IPK column */ iParent = regData; } sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v); sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL); } sqlite3VdbeGoto(v, iOk); } sqlite3VdbeAddOp4(v, OP_MakeRecord, regTemp, nCol, regRec, sqlite3IndexAffinityStr(pParse->db,pIdx), nCol); sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regRec, 0); VdbeCoverage(v); sqlite3ReleaseTempReg(pParse, regRec); sqlite3ReleaseTempRange(pParse, regTemp, nCol); } } if( !pFKey->isDeferred && !(pParse->db->flags & SQLITE_DeferFKs) && !pParse->pToplevel && !pParse->isMultiWrite ){ /* Special case: If this is an INSERT statement that will insert exactly ** one row into the table, raise a constraint immediately instead of ** incrementing a counter. This is necessary as the VM code is being ** generated for will not open a statement transaction. */ assert( nIncr==1 ); sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY, OE_Abort, 0, P4_STATIC, P5_ConstraintFK); }else{ if( nIncr>0 && pFKey->isDeferred==0 ){ sqlite3MayAbort(pParse); } sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); } sqlite3VdbeResolveLabel(v, iOk); sqlite3VdbeAddOp1(v, OP_Close, iCur); } /* ** Return an Expr object that refers to a memory register corresponding ** to column iCol of table pTab. ** ** regBase is the first of an array of register that contains the data ** for pTab. regBase itself holds the rowid. regBase+1 holds the first ** column. regBase+2 holds the second column, and so forth. */ static Expr *exprTableRegister( Parse *pParse, /* Parsing and code generating context */ Table *pTab, /* The table whose content is at r[regBase]... */ int regBase, /* Contents of table pTab */ i16 iCol /* Which column of pTab is desired */ ){ Expr *pExpr; Column *pCol; const char *zColl; sqlite3 *db = pParse->db; pExpr = sqlite3Expr(db, TK_REGISTER, 0); if( pExpr ){ if( iCol>=0 && iCol!=pTab->iPKey ){ pCol = &pTab->aCol[iCol]; pExpr->iTable = regBase + iCol + 1; pExpr->affinity = pCol->affinity; zColl = pCol->zColl; if( zColl==0 ) zColl = db->pDfltColl->zName; pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl); }else{ pExpr->iTable = regBase; pExpr->affinity = SQLITE_AFF_INTEGER; } } return pExpr; } /* ** Return an Expr object that refers to column iCol of table pTab which ** has cursor iCur. */ static Expr *exprTableColumn( sqlite3 *db, /* The database connection */ Table *pTab, /* The table whose column is desired */ int iCursor, /* The open cursor on the table */ i16 iCol /* The column that is wanted */ ){ Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0); if( pExpr ){ pExpr->pTab = pTab; pExpr->iTable = iCursor; pExpr->iColumn = iCol; } return pExpr; } /* ** This function is called to generate code executed when a row is deleted ** from the parent table of foreign key constraint pFKey and, if pFKey is ** deferred, when a row is inserted into the same table. When generating ** code for an SQL UPDATE operation, this function may be called twice - ** once to "delete" the old row and once to "insert" the new row. ** ** Parameter nIncr is passed -1 when inserting a row (as this may decrease ** the number of FK violations in the db) or +1 when deleting one (as this ** may increase the number of FK constraint problems). ** ** The code generated by this function scans through the rows in the child ** table that correspond to the parent table row being deleted or inserted. ** For each child row found, one of the following actions is taken: ** ** Operation | FK type | Action taken ** -------------------------------------------------------------------------- ** DELETE immediate Increment the "immediate constraint counter". ** Or, if the ON (UPDATE|DELETE) action is RESTRICT, ** throw a "FOREIGN KEY constraint failed" exception. ** ** INSERT immediate Decrement the "immediate constraint counter". ** ** DELETE deferred Increment the "deferred constraint counter". ** Or, if the ON (UPDATE|DELETE) action is RESTRICT, ** throw a "FOREIGN KEY constraint failed" exception. ** ** 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 ); assert( pIdx!=0 || HasRowid(pTab) ); if( nIncr<0 ){ iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0); VdbeCoverage(v); } /* Create an Expr object representing an SQL expression like: ** ** <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ... ** ** The collation sequence used for the comparison should be that of ** the parent key columns. The affinity of the parent key column should ** be applied to each child key value before the comparison takes place. */ for(i=0; i<pFKey->nCol; i++){ Expr *pLeft; /* Value from parent table row */ Expr *pRight; /* Column ref to child table */ Expr *pEq; /* Expression (pLeft = pRight) */ i16 iCol; /* Index of column in child table */ const char *zCol; /* Name of column in child table */ iCol = pIdx ? pIdx->aiColumn[i] : -1; pLeft = exprTableRegister(pParse, pTab, regData, iCol); iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom; assert( iCol>=0 ); zCol = pFKey->pFrom->aCol[iCol].zName; pRight = sqlite3Expr(db, TK_ID, zCol); pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight); pWhere = sqlite3ExprAnd(db, pWhere, pEq); } /* If the child table is the same as the parent table, then add terms ** to the WHERE clause that prevent this entry from being scanned. ** The added WHERE clause terms are like this: ** ** $current_rowid!=rowid ** NOT( $current_a==a AND $current_b==b AND ... ) ** ** The first form is used for rowid tables. The second form is used ** for WITHOUT ROWID tables. In the second form, the primary key is ** (a,b,...) */ if( pTab==pFKey->pFrom && nIncr>0 ){ Expr *pNe; /* Expression (pLeft != pRight) */ Expr *pLeft; /* Value from parent table row */ Expr *pRight; /* Column ref to child table */ if( HasRowid(pTab) ){ pLeft = exprTableRegister(pParse, pTab, regData, -1); pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1); pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight); }else{ Expr *pEq, *pAll = 0; Index *pPk = sqlite3PrimaryKeyIndex(pTab); assert( pIdx!=0 ); for(i=0; i<pPk->nKeyCol; i++){ i16 iCol = pIdx->aiColumn[i]; assert( iCol>=0 ); pLeft = exprTableRegister(pParse, pTab, regData, iCol); pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, iCol); pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight); pAll = sqlite3ExprAnd(db, pAll, pEq); } pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 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); /* Create VDBE to loop through the entries in pSrc that match the WHERE ** clause. For each row found, increment either the deferred or immediate ** foreign key constraint counter. */ if( pParse->nErr==0 ){ pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0, 0); sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); if( pWInfo ){ sqlite3WhereEnd(pWInfo); } } /* Clean up the WHERE clause constructed above. */ 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 ** "t2". Calling this function with "t2" as the argument would return a ** NULL pointer (as there are no FK constraints for which t2 is the parent ** table). */ FKey *sqlite3FkReferences(Table *pTab){ return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName); } /* ** The second argument is a Trigger structure allocated by the ** fkActionTrigger() routine. This function deletes the Trigger structure ** and all of its sub-components. ** ** The Trigger structure or any of its sub-components may be allocated from ** the lookaside buffer belonging to database handle dbMem. */ static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){ if( p ){ TriggerStep *pStep = p->step_list; sqlite3ExprDelete(dbMem, pStep->pWhere); sqlite3ExprListDelete(dbMem, pStep->pExprList); sqlite3SelectDelete(dbMem, pStep->pSelect); sqlite3ExprDelete(dbMem, p->pWhen); sqlite3DbFree(dbMem, p); } } /* ** This function is called to generate code that runs when table pTab is ** being dropped from the database. The SrcList passed as the second argument ** to this function contains a single entry guaranteed to resolve to ** table pTab. ** ** Normally, no code is required. However, if either ** ** (a) The table is the parent table of a FK constraint, or ** (b) The table is the child table of a deferred FK constraint and it is ** determined at runtime that there are outstanding deferred FK ** constraint violations in the database, ** ** then the equivalent of "DELETE FROM <tbl>" is executed before dropping ** the table from the database. Triggers are disabled while running this ** DELETE, but foreign key actions are not. */ void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){ sqlite3 *db = pParse->db; if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){ int iSkip = 0; Vdbe *v = sqlite3GetVdbe(pParse); assert( v ); /* VDBE has already been allocated */ if( sqlite3FkReferences(pTab)==0 ){ /* Search for a deferred foreign key constraint for which this table ** is the child table. If one cannot be found, return without ** generating any VDBE code. If one can be found, then jump over ** the entire DELETE if there are no outstanding deferred constraints ** when this statement is run. */ FKey *p; for(p=pTab->pFKey; p; p=p->pNextFrom){ if( p->isDeferred || (db->flags & SQLITE_DeferFKs) ) break; } if( !p ) return; iSkip = sqlite3VdbeMakeLabel(v); sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v); } pParse->disableTriggers = 1; sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0); pParse->disableTriggers = 0; /* If the DELETE has generated immediate foreign key constraint ** violations, halt the VDBE and return an error at this point, before ** any modifications to the schema are made. This is because statement ** transactions are not able to rollback schema changes. ** ** If the SQLITE_DeferFKs flag is set, then this is not required, as ** the statement transaction will not be rolled back even if FK ** constraints are violated. */ if( (db->flags & SQLITE_DeferFKs)==0 ){ sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2); VdbeCoverage(v); sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY, OE_Abort, 0, P4_STATIC, P5_ConstraintFK); } if( iSkip ){ sqlite3VdbeResolveLabel(v, iSkip); } } } /* ** The second argument points to an FKey object representing a foreign key ** for which pTab is the child table. An UPDATE statement against pTab ** is currently being processed. For each column of the table that is ** actually updated, the corresponding element in the aChange[] array ** is zero or greater (if a column is unmodified the corresponding element ** is set to -1). If the rowid column is modified by the UPDATE statement ** the bChngRowid argument is non-zero. ** ** This function returns true if any of the columns that are part of the ** child key for FK constraint *p are modified. */ static int fkChildIsModified( Table *pTab, /* Table being updated */ FKey *p, /* Foreign key for which pTab is the child */ int *aChange, /* Array indicating modified columns */ int bChngRowid /* True if rowid is modified by this update */ ){ int i; for(i=0; i<p->nCol; i++){ int iChildKey = p->aCol[i].iFrom; if( aChange[iChildKey]>=0 ) return 1; if( iChildKey==pTab->iPKey && bChngRowid ) return 1; } return 0; } /* ** The second argument points to an FKey object representing a foreign key ** for which pTab is the parent table. An UPDATE statement against pTab ** is currently being processed. For each column of the table that is ** actually updated, the corresponding element in the aChange[] array ** is zero or greater (if a column is unmodified the corresponding element ** is set to -1). If the rowid column is modified by the UPDATE statement ** the bChngRowid argument is non-zero. ** ** This function returns true if any of the columns that are part of the ** parent key for FK constraint *p are modified. */ static int fkParentIsModified( Table *pTab, FKey *p, int *aChange, int bChngRowid ){ int i; for(i=0; i<p->nCol; i++){ char *zKey = p->aCol[i].zCol; int iKey; for(iKey=0; iKey<pTab->nCol; iKey++){ if( aChange[iKey]>=0 || (iKey==pTab->iPKey && bChngRowid) ){ Column *pCol = &pTab->aCol[iKey]; if( zKey ){ if( 0==sqlite3StrICmp(pCol->zName, zKey) ) return 1; }else if( pCol->colFlags & COLFLAG_PRIMKEY ){ return 1; } } } } return 0; } /* ** Return true if the parser passed as the first argument is being ** used to code a trigger that is really a "SET NULL" action belonging ** to trigger pFKey. */ static int isSetNullAction(Parse *pParse, FKey *pFKey){ Parse *pTop = sqlite3ParseToplevel(pParse); if( pTop->pTriggerPrg ){ Trigger *p = pTop->pTriggerPrg->pTrigger; if( (p==pFKey->apTrigger[0] && pFKey->aAction[0]==OE_SetNull) || (p==pFKey->apTrigger[1] && pFKey->aAction[1]==OE_SetNull) ){ return 1; } } return 0; } /* ** This function is called when inserting, deleting or updating a row of ** table pTab to generate VDBE code to perform foreign key constraint ** processing for the operation. ** ** For a DELETE operation, parameter regOld is passed the index of the ** first register in an array of (pTab->nCol+1) registers containing the ** rowid of the row being deleted, followed by each of the column values ** of the row being deleted, from left to right. Parameter regNew is passed ** zero in this case. ** ** For an INSERT operation, regOld is passed zero and regNew is passed the ** first register of an array of (pTab->nCol+1) registers containing the new ** row data. ** ** For an UPDATE operation, this function is called twice. Once before ** the original record is deleted from the table using the calling convention ** described for DELETE. Then again after the original record is deleted ** but before the new record is inserted using the INSERT convention. */ void sqlite3FkCheck( Parse *pParse, /* Parse context */ Table *pTab, /* Row is being deleted from this table */ int regOld, /* Previous row data is stored here */ int regNew, /* New row data is stored here */ int *aChange, /* Array indicating UPDATEd columns (or 0) */ int bChngRowid /* True if rowid is UPDATEd */ ){ sqlite3 *db = pParse->db; /* Database handle */ FKey *pFKey; /* Used to iterate through FKs */ int iDb; /* Index of database containing pTab */ const char *zDb; /* Name of database containing pTab */ int isIgnoreErrors = pParse->disableTriggers; /* Exactly one of regOld and regNew should be non-zero. */ assert( (regOld==0)!=(regNew==0) ); /* If foreign-keys are disabled, this function is a no-op. */ if( (db->flags&SQLITE_ForeignKeys)==0 ) return; iDb = sqlite3SchemaToIndex(db, pTab->pSchema); zDb = db->aDb[iDb].zDbSName; /* Loop through all the foreign key constraints for which pTab is the ** child table (the table that the foreign key definition is part of). */ for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){ Table *pTo; /* Parent table of foreign key pFKey */ Index *pIdx = 0; /* Index on key columns in pTo */ int *aiFree = 0; int *aiCol; int iCol; int i; int bIgnore = 0; if( aChange && sqlite3_stricmp(pTab->zName, pFKey->zTo)!=0 && fkChildIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){ continue; } /* Find the parent table of this foreign key. Also find a unique index ** on the parent key columns in the parent table. If either of these ** schema items cannot be located, set an error in pParse and return ** early. */ if( pParse->disableTriggers ){ pTo = sqlite3FindTable(db, pFKey->zTo, zDb); }else{ pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb); } if( !pTo || sqlite3FkLocateIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){ assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) ); if( !isIgnoreErrors || db->mallocFailed ) return; if( pTo==0 ){ /* If isIgnoreErrors is true, then a table is being dropped. In this ** case SQLite runs a "DELETE FROM xxx" on the table being dropped ** before actually dropping it in order to check FK constraints. ** If the parent table of an FK constraint on the current table is ** missing, behave as if it is empty. i.e. decrement the relevant ** FK counter for each row of the current table with non-NULL keys. */ Vdbe *v = sqlite3GetVdbe(pParse); int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1; for(i=0; i<pFKey->nCol; i++){ int iReg = pFKey->aCol[i].iFrom + regOld + 1; sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump); VdbeCoverage(v); } sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1); } continue; } assert( pFKey->nCol==1 || (aiFree && pIdx) ); if( aiFree ){ aiCol = aiFree; }else{ iCol = pFKey->aCol[0].iFrom; aiCol = &iCol; } for(i=0; i<pFKey->nCol; i++){ if( aiCol[i]==pTab->iPKey ){ aiCol[i] = -1; } assert( pIdx==0 || pIdx->aiColumn[i]>=0 ); #ifndef SQLITE_OMIT_AUTHORIZATION /* Request permission to read the parent key columns. If the ** authorization callback returns SQLITE_IGNORE, behave as if any ** values read from the parent table are NULL. */ if( db->xAuth ){ int rcauth; char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zName; rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb); bIgnore = (rcauth==SQLITE_IGNORE); } #endif } /* Take a shared-cache advisory read-lock on the parent table. Allocate ** a cursor to use to search the unique index on the parent key columns ** in the parent table. */ sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName); pParse->nTab++; if( regOld!=0 ){ /* A row is being removed from the child table. Search for the parent. ** If the parent does not exist, removing the child row resolves an ** outstanding foreign key constraint violation. */ fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1, bIgnore); } if( regNew!=0 && !isSetNullAction(pParse, pFKey) ){ /* A row is being added to the child table. If a parent row cannot ** be found, adding the child row has violated the FK constraint. ** ** If this operation is being performed as part of a trigger program ** that is actually a "SET NULL" action belonging to this very ** foreign key, then omit this scan altogether. As all child key ** values are guaranteed to be NULL, it is not possible for adding ** this row to cause an FK violation. */ fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1, bIgnore); } 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( !pFKey->isDeferred && !(db->flags & SQLITE_DeferFKs) && !pParse->pToplevel && !pParse->isMultiWrite ){ assert( regOld==0 && regNew!=0 ); /* Inserting a single row into a parent table cannot cause (or fix) ** an immediate foreign key violation. So do nothing in this case. */ continue; } if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){ if( !isIgnoreErrors || db->mallocFailed ) return; |
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