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
  36 /*
  37 ** This object contains information needed to implement a single nested
  38 ** loop in WHERE clause.
  39 **
  40 ** Contrast this object with WhereLoop.  This object describes the
  41 ** implementation of the loop.  WhereLoop describes the algorithm.
  42 ** This object contains a pointer to the WhereLoop algorithm as one of
  43 ** its elements.
  44 **
  45 ** The WhereInfo object contains a single instance of this object for
  46 ** each term in the FROM clause (which is to say, for each of the
  47 ** nested loops as implemented).  The order of WhereLevel objects determines
  48 ** the loop nested order, with WhereInfo.a[0] being the outer loop and
  49 ** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop.
  50 */
  51 struct WhereLevel {
  52   int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */
  53   int iTabCur;          /* The VDBE cursor used to access the table */
  54   int iIdxCur;          /* The VDBE cursor used to access pIdx */
  55   int addrBrk;          /* Jump here to break out of the loop */
  56   int addrNxt;          /* Jump here to start the next IN combination */
  57   int addrSkip;         /* Jump here for next iteration of skip-scan */
  58   int addrCont;         /* Jump here to continue with the next loop cycle */
  59   int addrFirst;        /* First instruction of interior of the loop */
  60   int addrBody;         /* Beginning of the body of this loop */
  61   int regBignull;       /* big-null flag reg. True if a NULL-scan is needed */
  62   int addrBignull;      /* Jump here for next part of big-null scan */
  63 #ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
  64   u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */
  65   int addrLikeRep;      /* LIKE range processing address */
  66 #endif
  67   u8 iFrom;             /* Which entry in the FROM clause */
  68   u8 op, p3, p5;        /* Opcode, P3 & P5 of the opcode that ends the loop */
  69   int p1, p2;           /* Operands of the opcode used to end the loop */
  70   union {               /* Information that depends on pWLoop->wsFlags */
  71     struct {
  72       int nIn;              /* Number of entries in aInLoop[] */
  73       struct InLoop {
  74         int iCur;              /* The VDBE cursor used by this IN operator */
  75         int addrInTop;         /* Top of the IN loop */
  76         int iBase;             /* Base register of multi-key index record */
  77         int nPrefix;           /* Number of prior entires in the key */
  78         u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
  79       } *aInLoop;           /* Information about each nested IN operator */
  80     } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
  81     Index *pCovidx;       /* Possible covering index for WHERE_MULTI_OR */
  82   } u;
  83   struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
  84   Bitmask notReady;          /* FROM entries not usable at this level */
  85 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  86   int addrVisit;        /* Address at which row is visited */
  87 #endif
  88 };
  89
  90 /*
  91 ** Each instance of this object represents an algorithm for evaluating one
  92 ** term of a join.  Every term of the FROM clause will have at least
  93 ** one corresponding WhereLoop object (unless INDEXED BY constraints
  94 ** prevent a query solution - which is an error) and many terms of the
  95 ** FROM clause will have multiple WhereLoop objects, each describing a
  96 ** potential way of implementing that FROM-clause term, together with
  97 ** dependencies and cost estimates for using the chosen algorithm.
  98 **
  99 ** Query planning consists of building up a collection of these WhereLoop
 100 ** objects, then computing a particular sequence of WhereLoop objects, with
 101 ** one WhereLoop object per FROM clause term, that satisfy all dependencies
 102 ** and that minimize the overall cost.
 103 */
 104 struct WhereLoop {
 105   Bitmask prereq;       /* Bitmask of other loops that must run first */
 106   Bitmask maskSelf;     /* Bitmask identifying table iTab */
 107 #ifdef SQLITE_DEBUG
 108   char cId;             /* Symbolic ID of this loop for debugging use */
 109 #endif
 110   u8 iTab;              /* Position in FROM clause of table for this loop */
 111   u8 iSortIdx;          /* Sorting index number.  0==None */
 112   LogEst rSetup;        /* One-time setup cost (ex: create transient index) */
 113   LogEst rRun;          /* Cost of running each loop */
 114   LogEst nOut;          /* Estimated number of output rows */
 115   union {
 116     struct {               /* Information for internal btree tables */
 117       u16 nEq;               /* Number of equality constraints */
 118       u16 nBtm;              /* Size of BTM vector */
 119       u16 nTop;              /* Size of TOP vector */
 120       u16 nDistinctCol;      /* Index columns used to sort for DISTINCT */
 121       Index *pIndex;         /* Index used, or NULL */
 122     } btree;
 123     struct {               /* Information for virtual tables */
 124       int idxNum;            /* Index number */
 125       u8 needFree;           /* True if sqlite3_free(idxStr) is needed */
 126       i8 isOrdered;          /* True if satisfies ORDER BY */
 127       u16 omitMask;          /* Terms that may be omitted */
 128       char *idxStr;          /* Index identifier string */
 129     } vtab;
 130   } u;
 131   u32 wsFlags;          /* WHERE_* flags describing the plan */
 132   u16 nLTerm;           /* Number of entries in aLTerm[] */
 133   u16 nSkip;            /* Number of NULL aLTerm[] entries */
 134   /**** whereLoopXfer() copies fields above ***********************/
 135 # define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
 136   u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
 137   WhereTerm **aLTerm;   /* WhereTerms used */
 138   WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
 139   WhereTerm *aLTermSpace[3];  /* Initial aLTerm[] space */
 140 };
 141
 142 /* This object holds the prerequisites and the cost of running a
 143 ** subquery on one operand of an OR operator in the WHERE clause.
 144 ** See WhereOrSet for additional information
 145 */
 146 struct WhereOrCost {
 147   Bitmask prereq;     /* Prerequisites */
 148   LogEst rRun;        /* Cost of running this subquery */
 149   LogEst nOut;        /* Number of outputs for this subquery */
 150 };
 151
 152 /* The WhereOrSet object holds a set of possible WhereOrCosts that
 153 ** correspond to the subquery(s) of OR-clause processing.  Only the
 154 ** best N_OR_COST elements are retained.
 155 */
 156 #define N_OR_COST 3
 157 struct WhereOrSet {
 158   u16 n;                      /* Number of valid a[] entries */
 159   WhereOrCost a[N_OR_COST];   /* Set of best costs */
 160 };
 161
 162 /*
 163 ** Each instance of this object holds a sequence of WhereLoop objects
 164 ** that implement some or all of a query plan.
 165 **
 166 ** Think of each WhereLoop object as a node in a graph with arcs
 167 ** showing dependencies and costs for travelling between nodes.  (That is
 168 ** not a completely accurate description because WhereLoop costs are a
 169 ** vector, not a scalar, and because dependencies are many-to-one, not
 170 ** one-to-one as are graph nodes.  But it is a useful visualization aid.)
 171 ** Then a WherePath object is a path through the graph that visits some
 172 ** or all of the WhereLoop objects once.
 173 **
 174 ** The "solver" works by creating the N best WherePath objects of length
 175 ** 1.  Then using those as a basis to compute the N best WherePath objects
 176 ** of length 2.  And so forth until the length of WherePaths equals the
 177 ** number of nodes in the FROM clause.  The best (lowest cost) WherePath
 178 ** at the end is the chosen query plan.
 179 */
 180 struct WherePath {
 181   Bitmask maskLoop;     /* Bitmask of all WhereLoop objects in this path */
 182   Bitmask revLoop;      /* aLoop[]s that should be reversed for ORDER BY */
 183   LogEst nRow;          /* Estimated number of rows generated by this path */
 184   LogEst rCost;         /* Total cost of this path */
 185   LogEst rUnsorted;     /* Total cost of this path ignoring sorting costs */
 186   i8 isOrdered;         /* No. of ORDER BY terms satisfied. -1 for unknown */
 187   WhereLoop **aLoop;    /* Array of WhereLoop objects implementing this path */
 188 };
 189
 190 /*
 191 ** The query generator uses an array of instances of this structure to
 192 ** help it analyze the subexpressions of the WHERE clause.  Each WHERE
 193 ** clause subexpression is separated from the others by AND operators,
 194 ** usually, or sometimes subexpressions separated by OR.
 195 **
 196 ** All WhereTerms are collected into a single WhereClause structure.
 197 ** The following identity holds:
 198 **
 199 **        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
 200 **
 201 ** When a term is of the form:
 202 **
 203 **              X <op> <expr>
 204 **
 205 ** where X is a column name and <op> is one of certain operators,
 206 ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
 207 ** cursor number and column number for X.  WhereTerm.eOperator records
 208 ** the <op> using a bitmask encoding defined by WO_xxx below.  The
 209 ** use of a bitmask encoding for the operator allows us to search
 210 ** quickly for terms that match any of several different operators.
 211 **
 212 ** A WhereTerm might also be two or more subterms connected by OR:
 213 **
 214 **         (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
 215 **
 216 ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR
 217 ** and the WhereTerm.u.pOrInfo field points to auxiliary information that
 218 ** is collected about the OR clause.
 219 **
 220 ** If a term in the WHERE clause does not match either of the two previous
 221 ** categories, then eOperator==0.  The WhereTerm.pExpr field is still set
 222 ** to the original subexpression content and wtFlags is set up appropriately
 223 ** but no other fields in the WhereTerm object are meaningful.
 224 **
 225 ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
 226 ** but they do so indirectly.  A single WhereMaskSet structure translates
 227 ** cursor number into bits and the translated bit is stored in the prereq
 228 ** fields.  The translation is used in order to maximize the number of
 229 ** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
 230 ** spread out over the non-negative integers.  For example, the cursor
 231 ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The WhereMaskSet
 232 ** translates these sparse cursor numbers into consecutive integers
 233 ** beginning with 0 in order to make the best possible use of the available
 234 ** bits in the Bitmask.  So, in the example above, the cursor numbers
 235 ** would be mapped into integers 0 through 7.
 236 **
 237 ** The number of terms in a join is limited by the number of bits
 238 ** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
 239 ** is only able to process joins with 64 or fewer tables.
 240 */
 241 struct WhereTerm {
 242   Expr *pExpr;            /* Pointer to the subexpression that is this term */
 243   WhereClause *pWC;       /* The clause this term is part of */
 244   LogEst truthProb;       /* Probability of truth for this expression */
 245   u16 wtFlags;            /* TERM_xxx bit flags.  See below */
 246   u16 eOperator;          /* A WO_xx value describing <op> */
 247   u8 nChild;              /* Number of children that must disable us */
 248   u8 eMatchOp;            /* Op for vtab MATCH/LIKE/GLOB/REGEXP terms */
 249   int iParent;            /* Disable pWC->a[iParent] when this term disabled */
 250   int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
 251   union {
 252     struct {
 253       int leftColumn;         /* Column number of X in "X <op> <expr>" */
 254       int iField;             /* Field in (?,?,?) IN (SELECT...) vector */
 255     } x;                    /* Opcode other than OP_OR or OP_AND */
 256     WhereOrInfo *pOrInfo;   /* Extra information if (eOperator & WO_OR)!=0 */
 257     WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
 258   } u;
 259   Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
 260   Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
 261 };
 262
 263 /*
 264 ** Allowed values of WhereTerm.wtFlags
 265 */
 266 #define TERM_DYNAMIC    0x0001 /* Need to call sqlite3ExprDelete(db, pExpr) */
 267 #define TERM_VIRTUAL    0x0002 /* Added by the optimizer.  Do not code */
 268 #define TERM_CODED      0x0004 /* This term is already coded */
 269 #define TERM_COPIED     0x0008 /* Has a child */
 270 #define TERM_ORINFO     0x0010 /* Need to free the WhereTerm.u.pOrInfo object */
 271 #define TERM_ANDINFO    0x0020 /* Need to free the WhereTerm.u.pAndInfo obj */
 272 #define TERM_OR_OK      0x0040 /* Used during OR-clause processing */
 273 #define TERM_VNULL      0x0080 /* Manufactured x>NULL or x<=NULL term */
 274 #define TERM_LIKEOPT    0x0100 /* Virtual terms from the LIKE optimization */
 275 #define TERM_LIKECOND   0x0200 /* Conditionally this LIKE operator term */
 276 #define TERM_LIKE       0x0400 /* The original LIKE operator */
 277 #define TERM_IS         0x0800 /* Term.pExpr is an IS operator */
 278 #define TERM_VARSELECT  0x1000 /* Term.pExpr contains a correlated sub-query */
 279 #define TERM_HEURTRUTH  0x2000 /* Heuristic truthProb used */
 280 #ifdef SQLITE_ENABLE_STAT4
 281 #  define TERM_HIGHTRUTH  0x4000 /* Term excludes few rows */
 282 #else
 283 #  define TERM_HIGHTRUTH  0      /* Only used with STAT4 */
 284 #endif
 285
 286 /*
 287 ** An instance of the WhereScan object is used as an iterator for locating
 288 ** terms in the WHERE clause that are useful to the query planner.
 289 */
 290 struct WhereScan {
 291   WhereClause *pOrigWC;      /* Original, innermost WhereClause */
 292   WhereClause *pWC;          /* WhereClause currently being scanned */
 293   const char *zCollName;     /* Required collating sequence, if not NULL */
 294   Expr *pIdxExpr;            /* Search for this index expression */
 295   char idxaff;               /* Must match this affinity, if zCollName!=NULL */
 296   unsigned char nEquiv;      /* Number of entries in aiCur[] and aiColumn[] */
 297   unsigned char iEquiv;      /* Next unused slot in aiCur[] and aiColumn[] */
 298   u32 opMask;                /* Acceptable operators */
 299   int k;                     /* Resume scanning at this->pWC->a[this->k] */
 300   int aiCur[11];             /* Cursors in the equivalence class */
 301   i16 aiColumn[11];          /* Corresponding column number in the eq-class */
 302 };
 303
 304 /*
 305 ** An instance of the following structure holds all information about a
 306 ** WHERE clause.  Mostly this is a container for one or more WhereTerms.
 307 **
 308 ** Explanation of pOuter:  For a WHERE clause of the form
 309 **
 310 **           a AND ((b AND c) OR (d AND e)) AND f
 311 **
 312 ** There are separate WhereClause objects for the whole clause and for
 313 ** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
 314 ** subclauses points to the WhereClause object for the whole clause.
 315 */
 316 struct WhereClause {
 317   WhereInfo *pWInfo;       /* WHERE clause processing context */
 318   WhereClause *pOuter;     /* Outer conjunction */
 319   u8 op;                   /* Split operator.  TK_AND or TK_OR */
 320   u8 hasOr;                /* True if any a[].eOperator is WO_OR */
 321   int nTerm;               /* Number of terms */
 322   int nSlot;               /* Number of entries in a[] */
 323   WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
 324 #if defined(SQLITE_SMALL_STACK)
 325   WhereTerm aStatic[1];    /* Initial static space for a[] */
 326 #else
 327   WhereTerm aStatic[8];    /* Initial static space for a[] */
 328 #endif
 329 };
 330
 331 /*
 332 ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
 333 ** a dynamically allocated instance of the following structure.
 334 */
 335 struct WhereOrInfo {
 336   WhereClause wc;          /* Decomposition into subterms */
 337   Bitmask indexable;       /* Bitmask of all indexable tables in the clause */
 338 };
 339
 340 /*
 341 ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
 342 ** a dynamically allocated instance of the following structure.
 343 */
 344 struct WhereAndInfo {
 345   WhereClause wc;          /* The subexpression broken out */
 346 };
 347
 348 /*
 349 ** An instance of the following structure keeps track of a mapping
 350 ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
 351 **
 352 ** The VDBE cursor numbers are small integers contained in
 353 ** SrcList_item.iCursor and Expr.iTable fields.  For any given WHERE
 354 ** clause, the cursor numbers might not begin with 0 and they might
 355 ** contain gaps in the numbering sequence.  But we want to make maximum
 356 ** use of the bits in our bitmasks.  This structure provides a mapping
 357 ** from the sparse cursor numbers into consecutive integers beginning
 358 ** with 0.
 359 **
 360 ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
 361 ** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
 362 **
 363 ** For example, if the WHERE clause expression used these VDBE
 364 ** cursors:  4, 5, 8, 29, 57, 73.  Then the  WhereMaskSet structure
 365 ** would map those cursor numbers into bits 0 through 5.
 366 **
 367 ** Note that the mapping is not necessarily ordered.  In the example
 368 ** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
 369 ** 57->5, 73->4.  Or one of 719 other combinations might be used. It
 370 ** does not really matter.  What is important is that sparse cursor
 371 ** numbers all get mapped into bit numbers that begin with 0 and contain
 372 ** no gaps.
 373 */
 374 struct WhereMaskSet {
 375   int bVarSelect;               /* Used by sqlite3WhereExprUsage() */
 376   int n;                        /* Number of assigned cursor values */
 377   int ix[BMS];                  /* Cursor assigned to each bit */
 378 };
 379
 380 /*
 381 ** Initialize a WhereMaskSet object
 382 */
 383 #define initMaskSet(P)  (P)->n=0
 384
 385 /*
 386 ** This object is a convenience wrapper holding all information needed
 387 ** to construct WhereLoop objects for a particular query.
 388 */
 389 struct WhereLoopBuilder {
 390   WhereInfo *pWInfo;        /* Information about this WHERE */
 391   WhereClause *pWC;         /* WHERE clause terms */
 392   ExprList *pOrderBy;       /* ORDER BY clause */
 393   WhereLoop *pNew;          /* Template WhereLoop */
 394   WhereOrSet *pOrSet;       /* Record best loops here, if not NULL */
 395 #ifdef SQLITE_ENABLE_STAT4
 396   UnpackedRecord *pRec;     /* Probe for stat4 (if required) */
 397   int nRecValid;            /* Number of valid fields currently in pRec */
 398 #endif
 399   unsigned char bldFlags1;  /* First set of SQLITE_BLDF_* flags */
 400   unsigned char bldFlags2;  /* Second set of SQLITE_BLDF_* flags */
 401   unsigned int iPlanLimit;  /* Search limiter */
 402 };
 403
 404 /* Allowed values for WhereLoopBuider.bldFlags */
 405 #define SQLITE_BLDF1_INDEXED  0x0001   /* An index is used */
 406 #define SQLITE_BLDF1_UNIQUE   0x0002   /* All keys of a UNIQUE index used */
 407
 408 #define SQLITE_BLDF2_2NDPASS  0x0004   /* Second builder pass needed */
 409
 410 /* The WhereLoopBuilder.iPlanLimit is used to limit the number of
 411 ** index+constraint combinations the query planner will consider for a
 412 ** particular query.  If this parameter is unlimited, then certain
 413 ** pathological queries can spend excess time in the sqlite3WhereBegin()
 414 ** routine.  The limit is high enough that is should not impact real-world
 415 ** queries.
 416 **
 417 ** SQLITE_QUERY_PLANNER_LIMIT is the baseline limit.  The limit is
 418 ** increased by SQLITE_QUERY_PLANNER_LIMIT_INCR before each term of the FROM
 419 ** clause is processed, so that every table in a join is guaranteed to be
 420 ** able to propose a some index+constraint combinations even if the initial
 421 ** baseline limit was exhausted by prior tables of the join.
 422 */
 423 #ifndef SQLITE_QUERY_PLANNER_LIMIT
 424 # define SQLITE_QUERY_PLANNER_LIMIT 20000
 425 #endif
 426 #ifndef SQLITE_QUERY_PLANNER_LIMIT_INCR
 427 # define SQLITE_QUERY_PLANNER_LIMIT_INCR 1000
 428 #endif
 429
 430 /*
 431 ** Each instance of this object records a change to a single node
 432 ** in an expression tree to cause that node to point to a column
 433 ** of an index rather than an expression or a virtual column.  All
 434 ** such transformations need to be undone at the end of WHERE clause
 435 ** processing.
 436 */
 437 typedef struct WhereExprMod WhereExprMod;
 438 struct WhereExprMod {
 439   WhereExprMod *pNext;  /* Next translation on a list of them all */
 440   Expr *pExpr;          /* The Expr node that was transformed */
 441   Expr orig;            /* Original value of the Expr node */
 442 };
 443
 444 /*
 445 ** The WHERE clause processing routine has two halves.  The
 446 ** first part does the start of the WHERE loop and the second
 447 ** half does the tail of the WHERE loop.  An instance of
 448 ** this structure is returned by the first half and passed
 449 ** into the second half to give some continuity.
 450 **
 451 ** An instance of this object holds the complete state of the query
 452 ** planner.
 453 */
 454 struct WhereInfo {
 455   Parse *pParse;            /* Parsing and code generating context */
 456   SrcList *pTabList;        /* List of tables in the join */
 457   ExprList *pOrderBy;       /* The ORDER BY clause or NULL */
 458   ExprList *pResultSet;     /* Result set of the query */
 459   Expr *pWhere;             /* The complete WHERE clause */
 460   int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
 461   int iContinue;            /* Jump here to continue with next record */
 462   int iBreak;               /* Jump here to break out of the loop */
 463   int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
 464   u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
 465   LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
 466   u8 nLevel;                /* Number of nested loop */
 467   i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
 468   u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
 469   u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
 470   unsigned bDeferredSeek :1;   /* Uses OP_DeferredSeek */
 471   unsigned untestedTerms :1;   /* Not all WHERE terms resolved by outer loop */
 472   unsigned bOrderedInnerLoop:1;/* True if only the inner-most loop is ordered */
 473   unsigned sorted :1;          /* True if really sorted (not just grouped) */
 474   LogEst nRowOut;           /* Estimated number of output rows */
 475   int iTop;                 /* The very beginning of the WHERE loop */
 476   int iEndWhere;            /* End of the WHERE clause itself */
 477   WhereLoop *pLoops;        /* List of all WhereLoop objects */
 478   WhereExprMod *pExprMods;  /* Expression modifications */
 479   Bitmask revMask;          /* Mask of ORDER BY terms that need reversing */
 480   WhereClause sWC;          /* Decomposition of the WHERE clause */
 481   WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
 482   WhereLevel a[1];          /* Information about each nest loop in WHERE */
 483 };
 484
 485 /*
 486 ** Private interfaces - callable only by other where.c routines.
 487 **
 488 ** where.c:
 489 */
 490 Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
 491 #ifdef WHERETRACE_ENABLED
 492 void sqlite3WhereClausePrint(WhereClause *pWC);
 493 void sqlite3WhereTermPrint(WhereTerm *pTerm, int iTerm);
 494 void sqlite3WhereLoopPrint(WhereLoop *p, WhereClause *pWC);
 495 #endif
 496 WhereTerm *sqlite3WhereFindTerm(
 497   WhereClause *pWC,     /* The WHERE clause to be searched */
 498   int iCur,             /* Cursor number of LHS */
 499   int iColumn,          /* Column number of LHS */
 500   Bitmask notReady,     /* RHS must not overlap with this mask */
 501   u32 op,               /* Mask of WO_xx values describing operator */
 502   Index *pIdx           /* Must be compatible with this index, if not NULL */
 503 );
 504
 505 /* wherecode.c: */
 506 #ifndef SQLITE_OMIT_EXPLAIN
 507 int sqlite3WhereExplainOneScan(
 508   Parse *pParse,                  /* Parse context */
 509   SrcList *pTabList,              /* Table list this loop refers to */
 510   WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
 511   u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
 512 );
 513 #else
 514 # define sqlite3WhereExplainOneScan(u,v,w,x) 0
 515 #endif /* SQLITE_OMIT_EXPLAIN */
 516 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
 517 void sqlite3WhereAddScanStatus(
 518   Vdbe *v,                        /* Vdbe to add scanstatus entry to */
 519   SrcList *pSrclist,              /* FROM clause pLvl reads data from */
 520   WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
 521   int addrExplain                 /* Address of OP_Explain (or 0) */
 522 );
 523 #else
 524 # define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
 525 #endif
 526 Bitmask sqlite3WhereCodeOneLoopStart(
 527   Parse *pParse,       /* Parsing context */
 528   Vdbe *v,             /* Prepared statement under construction */
 529   WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
 530   int iLevel,          /* Which level of pWInfo->a[] should be coded */
 531   WhereLevel *pLevel,  /* The current level pointer */
 532   Bitmask notReady     /* Which tables are currently available */
 533 );
 534
 535 /* whereexpr.c: */
 536 void sqlite3WhereClauseInit(WhereClause*,WhereInfo*);
 537 void sqlite3WhereClauseClear(WhereClause*);
 538 void sqlite3WhereSplit(WhereClause*,Expr*,u8);
 539 Bitmask sqlite3WhereExprUsage(WhereMaskSet*, Expr*);
 540 Bitmask sqlite3WhereExprUsageNN(WhereMaskSet*, Expr*);
 541 Bitmask sqlite3WhereExprListUsage(WhereMaskSet*, ExprList*);
 542 void sqlite3WhereExprAnalyze(SrcList*, WhereClause*);
 543 void sqlite3WhereTabFuncArgs(Parse*, SrcItem*, WhereClause*);
 544
 545
 546
 547
 548
 549 /*
 550 ** Bitmasks for the operators on WhereTerm objects.  These are all
 551 ** operators that are of interest to the query planner.  An
 552 ** OR-ed combination of these values can be used when searching for
 553 ** particular WhereTerms within a WhereClause.
 554 **
 555 ** Value constraints:
 556 **     WO_EQ    == SQLITE_INDEX_CONSTRAINT_EQ
 557 **     WO_LT    == SQLITE_INDEX_CONSTRAINT_LT
 558 **     WO_LE    == SQLITE_INDEX_CONSTRAINT_LE
 559 **     WO_GT    == SQLITE_INDEX_CONSTRAINT_GT
 560 **     WO_GE    == SQLITE_INDEX_CONSTRAINT_GE
 561 */
 562 #define WO_IN     0x0001
 563 #define WO_EQ     0x0002
 564 #define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
 565 #define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
 566 #define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
 567 #define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
 568 #define WO_AUX    0x0040       /* Op useful to virtual tables only */
 569 #define WO_IS     0x0080
 570 #define WO_ISNULL 0x0100
 571 #define WO_OR     0x0200       /* Two or more OR-connected terms */
 572 #define WO_AND    0x0400       /* Two or more AND-connected terms */
 573 #define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
 574 #define WO_NOOP   0x1000       /* This term does not restrict search space */
 575
 576 #define WO_ALL    0x1fff       /* Mask of all possible WO_* values */
 577 #define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */
 578
 579 /*
 580 ** These are definitions of bits in the WhereLoop.wsFlags field.
 581 ** The particular combination of bits in each WhereLoop help to
 582 ** determine the algorithm that WhereLoop represents.
 583 */
 584 #define WHERE_COLUMN_EQ    0x00000001  /* x=EXPR */
 585 #define WHERE_COLUMN_RANGE 0x00000002  /* x<EXPR and/or x>EXPR */
 586 #define WHERE_COLUMN_IN    0x00000004  /* x IN (...) */
 587 #define WHERE_COLUMN_NULL  0x00000008  /* x IS NULL */
 588 #define WHERE_CONSTRAINT   0x0000000f  /* Any of the WHERE_COLUMN_xxx values */
 589 #define WHERE_TOP_LIMIT    0x00000010  /* x<EXPR or x<=EXPR constraint */
 590 #define WHERE_BTM_LIMIT    0x00000020  /* x>EXPR or x>=EXPR constraint */
 591 #define WHERE_BOTH_LIMIT   0x00000030  /* Both x>EXPR and x<EXPR */
 592 #define WHERE_IDX_ONLY     0x00000040  /* Use index only - omit table */
 593 #define WHERE_IPK          0x00000100  /* x is the INTEGER PRIMARY KEY */
 594 #define WHERE_INDEXED      0x00000200  /* WhereLoop.u.btree.pIndex is valid */
 595 #define WHERE_VIRTUALTABLE 0x00000400  /* WhereLoop.u.vtab is valid */
 596 #define WHERE_IN_ABLE      0x00000800  /* Able to support an IN operator */
 597 #define WHERE_ONEROW       0x00001000  /* Selects no more than one row */
 598 #define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
 599 #define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
 600 #define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
 601 #define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
 602 #define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
 603 #define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
 604 #define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */
 605 #define WHERE_IN_SEEKSCAN  0x00100000  /* Seek-scan optimization for IN */
 606 #define WHERE_TRANSCONS    0x00200000  /* Uses a transitive constraint */
 607
 608 #endif /* !defined(SQLITE_WHEREINT_H) */