src/whereInt.h

   1 /*
   2 ** 2013-11-12
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** This file contains structure and macro definitions for the query
  14 ** planner logic in "where.c".  These definitions are broken out into
  15 ** a separate source file for easier editing.
  16 */
  17 #ifndef SQLITE_WHEREINT_H
  18 #define SQLITE_WHEREINT_H
  19
  20
  21 /* Forward references
  22 */
  23 typedef struct WhereClause WhereClause;
  24 typedef struct WhereMaskSet WhereMaskSet;
  25 typedef struct WhereOrInfo WhereOrInfo;
  26 typedef struct WhereAndInfo WhereAndInfo;
  27 typedef struct WhereLevel WhereLevel;
  28 typedef struct WhereLoop WhereLoop;
  29 typedef struct WherePath WherePath;
  30 typedef struct WhereTerm WhereTerm;
  31 typedef struct WhereLoopBuilder WhereLoopBuilder;
  32 typedef struct WhereScan WhereScan;
  33 typedef struct WhereOrCost WhereOrCost;
  34 typedef struct WhereOrSet WhereOrSet;
  35 typedef struct WhereMemBlock WhereMemBlock;
  36 typedef struct WhereRightJoin WhereRightJoin;
  37
  38 /*
  39 ** This object is a header on a block of allocated memory that will be
  40 ** automatically freed when its WInfo object is destructed.
  41 */
  42 struct WhereMemBlock {
  43   WhereMemBlock *pNext;      /* Next block in the chain */
  44   u64 sz;                    /* Bytes of space */
  45 };
  46
  47 /*
  48 ** Extra information attached to a WhereLevel that is a RIGHT JOIN.
  49 */
  50 struct WhereRightJoin {
  51   int iMatch;          /* Cursor used to determine prior matched rows */
  52   int regBloom;        /* Bloom filter for iRJMatch */
  53   int regReturn;       /* Return register for the interior subroutine */
  54   int addrSubrtn;      /* Starting address for the interior subroutine */
  55   int endSubrtn;       /* The last opcode in the interior subroutine */
  56 };
  57
  58 /*
  59 ** This object contains information needed to implement a single nested
  60 ** loop in WHERE clause.
  61 **
  62 ** Contrast this object with WhereLoop.  This object describes the
  63 ** implementation of the loop.  WhereLoop describes the algorithm.
  64 ** This object contains a pointer to the WhereLoop algorithm as one of
  65 ** its elements.
  66 **
  67 ** The WhereInfo object contains a single instance of this object for
  68 ** each term in the FROM clause (which is to say, for each of the
  69 ** nested loops as implemented).  The order of WhereLevel objects determines
  70 ** the loop nested order, with WhereInfo.a[0] being the outer loop and
  71 ** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop.
  72 */
  73 struct WhereLevel {
  74   int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */
  75   int iTabCur;          /* The VDBE cursor used to access the table */
  76   int iIdxCur;          /* The VDBE cursor used to access pIdx */
  77   int addrBrk;          /* Jump here to break out of the loop */
  78   int addrNxt;          /* Jump here to start the next IN combination */
  79   int addrSkip;         /* Jump here for next iteration of skip-scan */
  80   int addrCont;         /* Jump here to continue with the next loop cycle */
  81   int addrFirst;        /* First instruction of interior of the loop */
  82   int addrBody;         /* Beginning of the body of this loop */
  83   int regBignull;       /* big-null flag reg. True if a NULL-scan is needed */
  84   int addrBignull;      /* Jump here for next part of big-null scan */
  85 #ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
  86   u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */
  87   int addrLikeRep;      /* LIKE range processing address */
  88 #endif
  89   int regFilter;        /* Bloom filter */
  90   WhereRightJoin *pRJ;  /* Extra information for RIGHT JOIN */
  91   u8 iFrom;             /* Which entry in the FROM clause */
  92   u8 op, p3, p5;        /* Opcode, P3 & P5 of the opcode that ends the loop */
  93   int p1, p2;           /* Operands of the opcode used to end the loop */
  94   union {               /* Information that depends on pWLoop->wsFlags */
  95     struct {
  96       int nIn;              /* Number of entries in aInLoop[] */
  97       struct InLoop {
  98         int iCur;              /* The VDBE cursor used by this IN operator */
  99         int addrInTop;         /* Top of the IN loop */
 100         int iBase;             /* Base register of multi-key index record */
 101         int nPrefix;           /* Number of prior entries in the key */
 102         u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
 103       } *aInLoop;           /* Information about each nested IN operator */
 104     } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
 105     Index *pCoveringIdx;  /* Possible covering index for WHERE_MULTI_OR */
 106   } u;
 107   struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
 108   Bitmask notReady;          /* FROM entries not usable at this level */
 109 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
 110   int addrVisit;        /* Address at which row is visited */
 111 #endif
 112 };
 113
 114 /*
 115 ** Each instance of this object represents an algorithm for evaluating one
 116 ** term of a join.  Every term of the FROM clause will have at least
 117 ** one corresponding WhereLoop object (unless INDEXED BY constraints
 118 ** prevent a query solution - which is an error) and many terms of the
 119 ** FROM clause will have multiple WhereLoop objects, each describing a
 120 ** potential way of implementing that FROM-clause term, together with
 121 ** dependencies and cost estimates for using the chosen algorithm.
 122 **
 123 ** Query planning consists of building up a collection of these WhereLoop
 124 ** objects, then computing a particular sequence of WhereLoop objects, with
 125 ** one WhereLoop object per FROM clause term, that satisfy all dependencies
 126 ** and that minimize the overall cost.
 127 */
 128 struct WhereLoop {
 129   Bitmask prereq;       /* Bitmask of other loops that must run first */
 130   Bitmask maskSelf;     /* Bitmask identifying table iTab */
 131 #ifdef SQLITE_DEBUG
 132   char cId;             /* Symbolic ID of this loop for debugging use */
 133 #endif
 134   u8 iTab;              /* Position in FROM clause of table for this loop */
 135   u8 iSortIdx;          /* Sorting index number.  0==None */
 136   LogEst rSetup;        /* One-time setup cost (ex: create transient index) */
 137   LogEst rRun;          /* Cost of running each loop */
 138   LogEst nOut;          /* Estimated number of output rows */
 139   union {
 140     struct {               /* Information for internal btree tables */
 141       u16 nEq;               /* Number of equality constraints */
 142       u16 nBtm;              /* Size of BTM vector */
 143       u16 nTop;              /* Size of TOP vector */
 144       u16 nDistinctCol;      /* Index columns used to sort for DISTINCT */
 145       Index *pIndex;         /* Index used, or NULL */
 146     } btree;
 147     struct {               /* Information for virtual tables */
 148       int idxNum;            /* Index number */
 149       u32 needFree : 1;      /* True if sqlite3_free(idxStr) is needed */
 150       u32 bOmitOffset : 1;   /* True to let virtual table handle offset */
 151       i8 isOrdered;          /* True if satisfies ORDER BY */
 152       u16 omitMask;          /* Terms that may be omitted */
 153       char *idxStr;          /* Index identifier string */
 154       u32 mHandleIn;         /* Terms to handle as IN(...) instead of == */
 155     } vtab;
 156   } u;
 157   u32 wsFlags;          /* WHERE_* flags describing the plan */
 158   u16 nLTerm;           /* Number of entries in aLTerm[] */
 159   u16 nSkip;            /* Number of NULL aLTerm[] entries */
 160   /**** whereLoopXfer() copies fields above ***********************/
 161 # define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
 162   u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
 163   LogEst rStarDelta;    /* Cost delta due to star-schema heuristic.  Not
 164                         ** initialized unless pWInfo->nOutStarDelta>0 */
 165   WhereTerm **aLTerm;   /* WhereTerms used */
 166   WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
 167   WhereTerm *aLTermSpace[3];  /* Initial aLTerm[] space */
 168 };
 169
 170 /* This object holds the prerequisites and the cost of running a
 171 ** subquery on one operand of an OR operator in the WHERE clause.
 172 ** See WhereOrSet for additional information
 173 */
 174 struct WhereOrCost {
 175   Bitmask prereq;     /* Prerequisites */
 176   LogEst rRun;        /* Cost of running this subquery */
 177   LogEst nOut;        /* Number of outputs for this subquery */
 178 };
 179
 180 /* The WhereOrSet object holds a set of possible WhereOrCosts that
 181 ** correspond to the subquery(s) of OR-clause processing.  Only the
 182 ** best N_OR_COST elements are retained.
 183 */
 184 #define N_OR_COST 3
 185 struct WhereOrSet {
 186   u16 n;                      /* Number of valid a[] entries */
 187   WhereOrCost a[N_OR_COST];   /* Set of best costs */
 188 };
 189
 190 /*
 191 ** Each instance of this object holds a sequence of WhereLoop objects
 192 ** that implement some or all of a query plan.
 193 **
 194 ** Think of each WhereLoop object as a node in a graph with arcs
 195 ** showing dependencies and costs for travelling between nodes.  (That is
 196 ** not a completely accurate description because WhereLoop costs are a
 197 ** vector, not a scalar, and because dependencies are many-to-one, not
 198 ** one-to-one as are graph nodes.  But it is a useful visualization aid.)
 199 ** Then a WherePath object is a path through the graph that visits some
 200 ** or all of the WhereLoop objects once.
 201 **
 202 ** The "solver" works by creating the N best WherePath objects of length
 203 ** 1.  Then using those as a basis to compute the N best WherePath objects
 204 ** of length 2.  And so forth until the length of WherePaths equals the
 205 ** number of nodes in the FROM clause.  The best (lowest cost) WherePath
 206 ** at the end is the chosen query plan.
 207 */
 208 struct WherePath {
 209   Bitmask maskLoop;     /* Bitmask of all WhereLoop objects in this path */
 210   Bitmask revLoop;      /* aLoop[]s that should be reversed for ORDER BY */
 211   LogEst nRow;          /* Estimated number of rows generated by this path */
 212   LogEst rCost;         /* Total cost of this path */
 213   LogEst rUnsorted;     /* Total cost of this path ignoring sorting costs */
 214   i8 isOrdered;         /* No. of ORDER BY terms satisfied. -1 for unknown */
 215   WhereLoop **aLoop;    /* Array of WhereLoop objects implementing this path */
 216 };
 217
 218 /*
 219 ** The query generator uses an array of instances of this structure to
 220 ** help it analyze the subexpressions of the WHERE clause.  Each WHERE
 221 ** clause subexpression is separated from the others by AND operators,
 222 ** usually, or sometimes subexpressions separated by OR.
 223 **
 224 ** All WhereTerms are collected into a single WhereClause structure.
 225 ** The following identity holds:
 226 **
 227 **        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
 228 **
 229 ** When a term is of the form:
 230 **
 231 **              X <op> <expr>
 232 **
 233 ** where X is a column name and <op> is one of certain operators,
 234 ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
 235 ** cursor number and column number for X.  WhereTerm.eOperator records
 236 ** the <op> using a bitmask encoding defined by WO_xxx below.  The
 237 ** use of a bitmask encoding for the operator allows us to search
 238 ** quickly for terms that match any of several different operators.
 239 **
 240 ** A WhereTerm might also be two or more subterms connected by OR:
 241 **
 242 **         (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
 243 **
 244 ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR
 245 ** and the WhereTerm.u.pOrInfo field points to auxiliary information that
 246 ** is collected about the OR clause.
 247 **
 248 ** If a term in the WHERE clause does not match either of the two previous
 249 ** categories, then eOperator==0.  The WhereTerm.pExpr field is still set
 250 ** to the original subexpression content and wtFlags is set up appropriately
 251 ** but no other fields in the WhereTerm object are meaningful.
 252 **
 253 ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
 254 ** but they do so indirectly.  A single WhereMaskSet structure translates
 255 ** cursor number into bits and the translated bit is stored in the prereq
 256 ** fields.  The translation is used in order to maximize the number of
 257 ** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
 258 ** spread out over the non-negative integers.  For example, the cursor
 259 ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The WhereMaskSet
 260 ** translates these sparse cursor numbers into consecutive integers
 261 ** beginning with 0 in order to make the best possible use of the available
 262 ** bits in the Bitmask.  So, in the example above, the cursor numbers
 263 ** would be mapped into integers 0 through 7.
 264 **
 265 ** The number of terms in a join is limited by the number of bits
 266 ** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
 267 ** is only able to process joins with 64 or fewer tables.
 268 */
 269 struct WhereTerm {
 270   Expr *pExpr;            /* Pointer to the subexpression that is this term */
 271   WhereClause *pWC;       /* The clause this term is part of */
 272   LogEst truthProb;       /* Probability of truth for this expression */
 273   u16 wtFlags;            /* TERM_xxx bit flags.  See below */
 274   u16 eOperator;          /* A WO_xx value describing <op> */
 275   u8 nChild;              /* Number of children that must disable us */
 276   u8 eMatchOp;            /* Op for vtab MATCH/LIKE/GLOB/REGEXP terms */
 277   int iParent;            /* Disable pWC->a[iParent] when this term disabled */
 278   int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
 279   union {
 280     struct {
 281       int leftColumn;         /* Column number of X in "X <op> <expr>" */
 282       int iField;             /* Field in (?,?,?) IN (SELECT...) vector */
 283     } x;                    /* Opcode other than OP_OR or OP_AND */
 284     WhereOrInfo *pOrInfo;   /* Extra information if (eOperator & WO_OR)!=0 */
 285     WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
 286   } u;
 287   Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
 288   Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
 289 };
 290
 291 /*
 292 ** Allowed values of WhereTerm.wtFlags
 293 */
 294 #define TERM_DYNAMIC    0x0001 /* Need to call sqlite3ExprDelete(db, pExpr) */
 295 #define TERM_VIRTUAL    0x0002 /* Added by the optimizer.  Do not code */
 296 #define TERM_CODED      0x0004 /* This term is already coded */
 297 #define TERM_COPIED     0x0008 /* Has a child */
 298 #define TERM_ORINFO     0x0010 /* Need to free the WhereTerm.u.pOrInfo object */
 299 #define TERM_ANDINFO    0x0020 /* Need to free the WhereTerm.u.pAndInfo obj */
 300 #define TERM_OK         0x0040 /* Used during OR-clause processing */
 301 #define TERM_VNULL      0x0080 /* Manufactured x>NULL or x<=NULL term */
 302 #define TERM_LIKEOPT    0x0100 /* Virtual terms from the LIKE optimization */
 303 #define TERM_LIKECOND   0x0200 /* Conditionally this LIKE operator term */
 304 #define TERM_LIKE       0x0400 /* The original LIKE operator */
 305 #define TERM_IS         0x0800 /* Term.pExpr is an IS operator */
 306 #define TERM_VARSELECT  0x1000 /* Term.pExpr contains a correlated sub-query */
 307 #define TERM_HEURTRUTH  0x2000 /* Heuristic truthProb used */
 308 #ifdef SQLITE_ENABLE_STAT4
 309 #  define TERM_HIGHTRUTH  0x4000 /* Term excludes few rows */
 310 #else
 311 #  define TERM_HIGHTRUTH  0      /* Only used with STAT4 */
 312 #endif
 313 #define TERM_SLICE      0x8000 /* One slice of a row-value/vector comparison */
 314
 315 /*
 316 ** An instance of the WhereScan object is used as an iterator for locating
 317 ** terms in the WHERE clause that are useful to the query planner.
 318 */
 319 struct WhereScan {
 320   WhereClause *pOrigWC;      /* Original, innermost WhereClause */
 321   WhereClause *pWC;          /* WhereClause currently being scanned */
 322   const char *zCollName;     /* Required collating sequence, if not NULL */
 323   Expr *pIdxExpr;            /* Search for this index expression */
 324   int k;                     /* Resume scanning at this->pWC->a[this->k] */
 325   u32 opMask;                /* Acceptable operators */
 326   char idxaff;               /* Must match this affinity, if zCollName!=NULL */
 327   unsigned char iEquiv;      /* Current slot in aiCur[] and aiColumn[] */
 328   unsigned char nEquiv;      /* Number of entries in aiCur[] and aiColumn[] */
 329   int aiCur[11];             /* Cursors in the equivalence class */
 330   i16 aiColumn[11];          /* Corresponding column number in the eq-class */
 331 };
 332
 333 /*
 334 ** An instance of the following structure holds all information about a
 335 ** WHERE clause.  Mostly this is a container for one or more WhereTerms.
 336 **
 337 ** Explanation of pOuter:  For a WHERE clause of the form
 338 **
 339 **           a AND ((b AND c) OR (d AND e)) AND f
 340 **
 341 ** There are separate WhereClause objects for the whole clause and for
 342 ** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
 343 ** subclauses points to the WhereClause object for the whole clause.
 344 */
 345 struct WhereClause {
 346   WhereInfo *pWInfo;       /* WHERE clause processing context */
 347   WhereClause *pOuter;     /* Outer conjunction */
 348   u8 op;                   /* Split operator.  TK_AND or TK_OR */
 349   u8 hasOr;                /* True if any a[].eOperator is WO_OR */
 350   int nTerm;               /* Number of terms */
 351   int nSlot;               /* Number of entries in a[] */
 352   int nBase;               /* Number of terms through the last non-Virtual */
 353   WhereTerm *a;            /* Each a[] describes a term of the WHERE clause */
 354 #if defined(SQLITE_SMALL_STACK)
 355   WhereTerm aStatic[1];    /* Initial static space for a[] */
 356 #else
 357   WhereTerm aStatic[8];    /* Initial static space for a[] */
 358 #endif
 359 };
 360
 361 /*
 362 ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
 363 ** a dynamically allocated instance of the following structure.
 364 */
 365 struct WhereOrInfo {
 366   WhereClause wc;          /* Decomposition into subterms */
 367   Bitmask indexable;       /* Bitmask of all indexable tables in the clause */
 368 };
 369
 370 /*
 371 ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
 372 ** a dynamically allocated instance of the following structure.
 373 */
 374 struct WhereAndInfo {
 375   WhereClause wc;          /* The subexpression broken out */
 376 };
 377
 378 /*
 379 ** An instance of the following structure keeps track of a mapping
 380 ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
 381 **
 382 ** The VDBE cursor numbers are small integers contained in
 383 ** SrcItem.iCursor and Expr.iTable fields.  For any given WHERE
 384 ** clause, the cursor numbers might not begin with 0 and they might
 385 ** contain gaps in the numbering sequence.  But we want to make maximum
 386 ** use of the bits in our bitmasks.  This structure provides a mapping
 387 ** from the sparse cursor numbers into consecutive integers beginning
 388 ** with 0.
 389 **
 390 ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
 391 ** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
 392 **
 393 ** For example, if the WHERE clause expression used these VDBE
 394 ** cursors:  4, 5, 8, 29, 57, 73.  Then the  WhereMaskSet structure
 395 ** would map those cursor numbers into bits 0 through 5.
 396 **
 397 ** Note that the mapping is not necessarily ordered.  In the example
 398 ** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
 399 ** 57->5, 73->4.  Or one of 719 other combinations might be used. It
 400 ** does not really matter.  What is important is that sparse cursor
 401 ** numbers all get mapped into bit numbers that begin with 0 and contain
 402 ** no gaps.
 403 */
 404 struct WhereMaskSet {
 405   int bVarSelect;               /* Used by sqlite3WhereExprUsage() */
 406   int n;                        /* Number of assigned cursor values */
 407   int ix[BMS];                  /* Cursor assigned to each bit */
 408 };
 409
 410 /*
 411 ** This object is a convenience wrapper holding all information needed
 412 ** to construct WhereLoop objects for a particular query.
 413 */
 414 struct WhereLoopBuilder {
 415   WhereInfo *pWInfo;        /* Information about this WHERE */
 416   WhereClause *pWC;         /* WHERE clause terms */
 417   WhereLoop *pNew;          /* Template WhereLoop */
 418   WhereOrSet *pOrSet;       /* Record best loops here, if not NULL */
 419 #ifdef SQLITE_ENABLE_STAT4
 420   UnpackedRecord *pRec;     /* Probe for stat4 (if required) */
 421   int nRecValid;            /* Number of valid fields currently in pRec */
 422 #endif
 423   unsigned char bldFlags1;  /* First set of SQLITE_BLDF_* flags */
 424   unsigned char bldFlags2;  /* Second set of SQLITE_BLDF_* flags */
 425   unsigned int iPlanLimit;  /* Search limiter */
 426 };
 427
 428 /* Allowed values for WhereLoopBuider.bldFlags */
 429 #define SQLITE_BLDF1_INDEXED  0x0001   /* An index is used */
 430 #define SQLITE_BLDF1_UNIQUE   0x0002   /* All keys of a UNIQUE index used */
 431
 432 #define SQLITE_BLDF2_2NDPASS  0x0004   /* Second builder pass needed */
 433
 434 /* The WhereLoopBuilder.iPlanLimit is used to limit the number of
 435 ** index+constraint combinations the query planner will consider for a
 436 ** particular query.  If this parameter is unlimited, then certain
 437 ** pathological queries can spend excess time in the sqlite3WhereBegin()
 438 ** routine.  The limit is high enough that is should not impact real-world
 439 ** queries.
 440 **
 441 ** SQLITE_QUERY_PLANNER_LIMIT is the baseline limit.  The limit is
 442 ** increased by SQLITE_QUERY_PLANNER_LIMIT_INCR before each term of the FROM
 443 ** clause is processed, so that every table in a join is guaranteed to be
 444 ** able to propose a some index+constraint combinations even if the initial
 445 ** baseline limit was exhausted by prior tables of the join.
 446 */
 447 #ifndef SQLITE_QUERY_PLANNER_LIMIT
 448 # define SQLITE_QUERY_PLANNER_LIMIT 20000
 449 #endif
 450 #ifndef SQLITE_QUERY_PLANNER_LIMIT_INCR
 451 # define SQLITE_QUERY_PLANNER_LIMIT_INCR 1000
 452 #endif
 453
 454 /*
 455 ** The WHERE clause processing routine has two halves.  The
 456 ** first part does the start of the WHERE loop and the second
 457 ** half does the tail of the WHERE loop.  An instance of
 458 ** this structure is returned by the first half and passed
 459 ** into the second half to give some continuity.
 460 **
 461 ** An instance of this object holds the complete state of the query
 462 ** planner.
 463 */
 464 struct WhereInfo {
 465   Parse *pParse;            /* Parsing and code generating context */
 466   SrcList *pTabList;        /* List of tables in the join */
 467   ExprList *pOrderBy;       /* The ORDER BY clause or NULL */
 468   ExprList *pResultSet;     /* Result set of the query */
 469 #if WHERETRACE_ENABLED
 470   Expr *pWhere;             /* The complete WHERE clause */
 471 #endif
 472   Select *pSelect;          /* The entire SELECT statement containing WHERE */
 473   int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
 474   int iContinue;            /* Jump here to continue with next record */
 475   int iBreak;               /* Jump here to break out of the loop */
 476   int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
 477   u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
 478   LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
 479   u8 nLevel;                /* Number of nested loop */
 480   i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
 481   u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
 482   u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
 483   unsigned bDeferredSeek :1;   /* Uses OP_DeferredSeek */
 484   unsigned untestedTerms :1;   /* Not all WHERE terms resolved by outer loop */
 485   unsigned bOrderedInnerLoop:1;/* True if only the inner-most loop is ordered */
 486   unsigned sorted :1;          /* True if really sorted (not just grouped) */
 487   LogEst nOutStarDelta;     /* Artifical nOut reduction for star-query */
 488   LogEst nRowOut;           /* Estimated number of output rows */
 489   int iTop;                 /* The very beginning of the WHERE loop */
 490   int iEndWhere;            /* End of the WHERE clause itself */
 491   WhereLoop *pLoops;        /* List of all WhereLoop objects */
 492   WhereMemBlock *pMemToFree;/* Memory to free when this object destroyed */
 493   Bitmask revMask;          /* Mask of ORDER BY terms that need reversing */
 494   WhereClause sWC;          /* Decomposition of the WHERE clause */
 495   WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
 496   WhereLevel a[1];          /* Information about each nest loop in WHERE */
 497 };
 498
 499 /*
 500 ** Private interfaces - callable only by other where.c routines.
 501 **
 502 ** where.c:
 503 */
 504 Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
 505 #ifdef WHERETRACE_ENABLED
 506 void sqlite3WhereClausePrint(WhereClause *pWC);
 507 void sqlite3WhereTermPrint(WhereTerm *pTerm, int iTerm);
 508 void sqlite3WhereLoopPrint(const WhereLoop *p, const WhereClause *pWC);
 509 #endif
 510 WhereTerm *sqlite3WhereFindTerm(
 511   WhereClause *pWC,     /* The WHERE clause to be searched */
 512   int iCur,             /* Cursor number of LHS */
 513   int iColumn,          /* Column number of LHS */
 514   Bitmask notReady,     /* RHS must not overlap with this mask */
 515   u32 op,               /* Mask of WO_xx values describing operator */
 516   Index *pIdx           /* Must be compatible with this index, if not NULL */
 517 );
 518 void *sqlite3WhereMalloc(WhereInfo *pWInfo, u64 nByte);
 519 void *sqlite3WhereRealloc(WhereInfo *pWInfo, void *pOld, u64 nByte);
 520
 521 /* wherecode.c: */
 522 #ifndef SQLITE_OMIT_EXPLAIN
 523 int sqlite3WhereExplainOneScan(
 524   Parse *pParse,                  /* Parse context */
 525   SrcList *pTabList,              /* Table list this loop refers to */
 526   WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
 527   u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
 528 );
 529 int sqlite3WhereExplainBloomFilter(
 530   const Parse *pParse,            /* Parse context */
 531   const WhereInfo *pWInfo,        /* WHERE clause */
 532   const WhereLevel *pLevel        /* Bloom filter on this level */
 533 );
 534 #else
 535 # define sqlite3WhereExplainOneScan(u,v,w,x) 0
 536 # define sqlite3WhereExplainBloomFilter(u,v,w) 0
 537 #endif /* SQLITE_OMIT_EXPLAIN */
 538 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
 539 void sqlite3WhereAddScanStatus(
 540   Vdbe *v,                        /* Vdbe to add scanstatus entry to */
 541   SrcList *pSrclist,              /* FROM clause pLvl reads data from */
 542   WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
 543   int addrExplain                 /* Address of OP_Explain (or 0) */
 544 );
 545 #else
 546 # define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
 547 #endif
 548 Bitmask sqlite3WhereCodeOneLoopStart(
 549   Parse *pParse,       /* Parsing context */
 550   Vdbe *v,             /* Prepared statement under construction */
 551   WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
 552   int iLevel,          /* Which level of pWInfo->a[] should be coded */
 553   WhereLevel *pLevel,  /* The current level pointer */
 554   Bitmask notReady     /* Which tables are currently available */
 555 );
 556 SQLITE_NOINLINE void sqlite3WhereRightJoinLoop(
 557   WhereInfo *pWInfo,
 558   int iLevel,
 559   WhereLevel *pLevel
 560 );
 561
 562 /* whereexpr.c: */
 563 void sqlite3WhereClauseInit(WhereClause*,WhereInfo*);
 564 void sqlite3WhereClauseClear(WhereClause*);
 565 void sqlite3WhereSplit(WhereClause*,Expr*,u8);
 566 void sqlite3WhereAddLimit(WhereClause*, Select*);
 567 Bitmask sqlite3WhereExprUsage(WhereMaskSet*, Expr*);
 568 Bitmask sqlite3WhereExprUsageNN(WhereMaskSet*, Expr*);
 569 Bitmask sqlite3WhereExprListUsage(WhereMaskSet*, ExprList*);
 570 void sqlite3WhereExprAnalyze(SrcList*, WhereClause*);
 571 void sqlite3WhereTabFuncArgs(Parse*, SrcItem*, WhereClause*);
 572
 573
 574
 575
 576
 577 /*
 578 ** Bitmasks for the operators on WhereTerm objects.  These are all
 579 ** operators that are of interest to the query planner.  An
 580 ** OR-ed combination of these values can be used when searching for
 581 ** particular WhereTerms within a WhereClause.
 582 **
 583 ** Value constraints:
 584 **     WO_EQ    == SQLITE_INDEX_CONSTRAINT_EQ
 585 **     WO_LT    == SQLITE_INDEX_CONSTRAINT_LT
 586 **     WO_LE    == SQLITE_INDEX_CONSTRAINT_LE
 587 **     WO_GT    == SQLITE_INDEX_CONSTRAINT_GT
 588 **     WO_GE    == SQLITE_INDEX_CONSTRAINT_GE
 589 */
 590 #define WO_IN     0x0001
 591 #define WO_EQ     0x0002
 592 #define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
 593 #define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
 594 #define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
 595 #define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
 596 #define WO_AUX    0x0040       /* Op useful to virtual tables only */
 597 #define WO_IS     0x0080
 598 #define WO_ISNULL 0x0100
 599 #define WO_OR     0x0200       /* Two or more OR-connected terms */
 600 #define WO_AND    0x0400       /* Two or more AND-connected terms */
 601 #define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
 602 #define WO_NOOP   0x1000       /* This term does not restrict search space */
 603 #define WO_ROWVAL 0x2000       /* A row-value term */
 604
 605 #define WO_ALL    0x3fff       /* Mask of all possible WO_* values */
 606 #define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */
 607
 608 /*
 609 ** These are definitions of bits in the WhereLoop.wsFlags field.
 610 ** The particular combination of bits in each WhereLoop help to
 611 ** determine the algorithm that WhereLoop represents.
 612 */
 613 #define WHERE_COLUMN_EQ    0x00000001  /* x=EXPR */
 614 #define WHERE_COLUMN_RANGE 0x00000002  /* x<EXPR and/or x>EXPR */
 615 #define WHERE_COLUMN_IN    0x00000004  /* x IN (...) */
 616 #define WHERE_COLUMN_NULL  0x00000008  /* x IS NULL */
 617 #define WHERE_CONSTRAINT   0x0000000f  /* Any of the WHERE_COLUMN_xxx values */
 618 #define WHERE_TOP_LIMIT    0x00000010  /* x<EXPR or x<=EXPR constraint */
 619 #define WHERE_BTM_LIMIT    0x00000020  /* x>EXPR or x>=EXPR constraint */
 620 #define WHERE_BOTH_LIMIT   0x00000030  /* Both x>EXPR and x<EXPR */
 621 #define WHERE_IDX_ONLY     0x00000040  /* Use index only - omit table */
 622 #define WHERE_IPK          0x00000100  /* x is the INTEGER PRIMARY KEY */
 623 #define WHERE_INDEXED      0x00000200  /* WhereLoop.u.btree.pIndex is valid */
 624 #define WHERE_VIRTUALTABLE 0x00000400  /* WhereLoop.u.vtab is valid */
 625 #define WHERE_IN_ABLE      0x00000800  /* Able to support an IN operator */
 626 #define WHERE_ONEROW       0x00001000  /* Selects no more than one row */
 627 #define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
 628 #define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
 629 #define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
 630 #define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
 631 #define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
 632 #define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
 633 #define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */
 634 #define WHERE_IN_SEEKSCAN  0x00100000  /* Seek-scan optimization for IN */
 635 #define WHERE_TRANSCONS    0x00200000  /* Uses a transitive constraint */
 636 #define WHERE_BLOOMFILTER  0x00400000  /* Consider using a Bloom-filter */
 637 #define WHERE_SELFCULL     0x00800000  /* nOut reduced by extra WHERE terms */
 638 #define WHERE_OMIT_OFFSET  0x01000000  /* Set offset counter to zero */
 639                       /*   0x02000000  -- available for reuse */
 640 #define WHERE_EXPRIDX      0x04000000  /* Uses an index-on-expressions */
 641
 642 #endif /* !defined(SQLITE_WHEREINT_H) */