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
  18 /*
  19 ** Trace output macros
  20 */
  21 #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  22 /***/ extern int sqlite3WhereTrace;
  23 #endif
  24 #if defined(SQLITE_DEBUG) \
  25     && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
  26 # define WHERETRACE(K,X)  if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X
  27 # define WHERETRACE_ENABLED 1
  28 #else
  29 # define WHERETRACE(K,X)
  30 #endif
  31
  32 /* Forward references
  33 */
  34 typedef struct WhereClause WhereClause;
  35 typedef struct WhereMaskSet WhereMaskSet;
  36 typedef struct WhereOrInfo WhereOrInfo;
  37 typedef struct WhereAndInfo WhereAndInfo;
  38 typedef struct WhereLevel WhereLevel;
  39 typedef struct WhereLoop WhereLoop;
  40 typedef struct WherePath WherePath;
  41 typedef struct WhereTerm WhereTerm;
  42 typedef struct WhereLoopBuilder WhereLoopBuilder;
  43 typedef struct WhereScan WhereScan;
  44 typedef struct WhereOrCost WhereOrCost;
  45 typedef struct WhereOrSet WhereOrSet;
  46
  47 /*
  48 ** This object contains information needed to implement a single nested
  49 ** loop in WHERE clause.
  50 **
  51 ** Contrast this object with WhereLoop.  This object describes the
  52 ** implementation of the loop.  WhereLoop describes the algorithm.
  53 ** This object contains a pointer to the WhereLoop algorithm as one of
  54 ** its elements.
  55 **
  56 ** The WhereInfo object contains a single instance of this object for
  57 ** each term in the FROM clause (which is to say, for each of the
  58 ** nested loops as implemented).  The order of WhereLevel objects determines
  59 ** the loop nested order, with WhereInfo.a[0] being the outer loop and
  60 ** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop.
  61 */
  62 struct WhereLevel {
  63   int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */
  64   int iTabCur;          /* The VDBE cursor used to access the table */
  65   int iIdxCur;          /* The VDBE cursor used to access pIdx */
  66   int addrBrk;          /* Jump here to break out of the loop */
  67   int addrNxt;          /* Jump here to start the next IN combination */
  68   int addrSkip;         /* Jump here for next iteration of skip-scan */
  69   int addrCont;         /* Jump here to continue with the next loop cycle */
  70   int addrFirst;        /* First instruction of interior of the loop */
  71   int addrBody;         /* Beginning of the body of this loop */
  72 #ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
  73   u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */
  74   int addrLikeRep;      /* LIKE range processing address */
  75 #endif
  76   u8 iFrom;             /* Which entry in the FROM clause */
  77   u8 op, p3, p5;        /* Opcode, P3 & P5 of the opcode that ends the loop */
  78   int p1, p2;           /* Operands of the opcode used to ends the loop */
  79   union {               /* Information that depends on pWLoop->wsFlags */
  80     struct {
  81       int nIn;              /* Number of entries in aInLoop[] */
  82       struct InLoop {
  83         int iCur;              /* The VDBE cursor used by this IN operator */
  84         int addrInTop;         /* Top of the IN loop */
  85         int iBase;             /* Base register of multi-key index record */
  86         int nPrefix;           /* Number of prior entires in the key */
  87         u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
  88       } *aInLoop;           /* Information about each nested IN operator */
  89     } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
  90     Index *pCovidx;       /* Possible covering index for WHERE_MULTI_OR */
  91   } u;
  92   struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
  93   Bitmask notReady;          /* FROM entries not usable at this level */
  94 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  95   int addrVisit;        /* Address at which row is visited */
  96 #endif
  97 };
  98
  99 /*
 100 ** Each instance of this object represents an algorithm for evaluating one
 101 ** term of a join.  Every term of the FROM clause will have at least
 102 ** one corresponding WhereLoop object (unless INDEXED BY constraints
 103 ** prevent a query solution - which is an error) and many terms of the
 104 ** FROM clause will have multiple WhereLoop objects, each describing a
 105 ** potential way of implementing that FROM-clause term, together with
 106 ** dependencies and cost estimates for using the chosen algorithm.
 107 **
 108 ** Query planning consists of building up a collection of these WhereLoop
 109 ** objects, then computing a particular sequence of WhereLoop objects, with
 110 ** one WhereLoop object per FROM clause term, that satisfy all dependencies
 111 ** and that minimize the overall cost.
 112 */
 113 struct WhereLoop {
 114   Bitmask prereq;       /* Bitmask of other loops that must run first */
 115   Bitmask maskSelf;     /* Bitmask identifying table iTab */
 116 #ifdef SQLITE_DEBUG
 117   char cId;             /* Symbolic ID of this loop for debugging use */
 118 #endif
 119   u8 iTab;              /* Position in FROM clause of table for this loop */
 120   u8 iSortIdx;          /* Sorting index number.  0==None */
 121   LogEst rSetup;        /* One-time setup cost (ex: create transient index) */
 122   LogEst rRun;          /* Cost of running each loop */
 123   LogEst nOut;          /* Estimated number of output rows */
 124   union {
 125     struct {               /* Information for internal btree tables */
 126       u16 nEq;               /* Number of equality constraints */
 127       u16 nBtm;              /* Size of BTM vector */
 128       u16 nTop;              /* Size of TOP vector */
 129       u16 nIdxCol;           /* Index column used for ORDER BY */
 130       Index *pIndex;         /* Index used, or NULL */
 131     } btree;
 132     struct {               /* Information for virtual tables */
 133       int idxNum;            /* Index number */
 134       u8 needFree;           /* True if sqlite3_free(idxStr) is needed */
 135       i8 isOrdered;          /* True if satisfies ORDER BY */
 136       u16 omitMask;          /* Terms that may be omitted */
 137       char *idxStr;          /* Index identifier string */
 138     } vtab;
 139   } u;
 140   u32 wsFlags;          /* WHERE_* flags describing the plan */
 141   u16 nLTerm;           /* Number of entries in aLTerm[] */
 142   u16 nSkip;            /* Number of NULL aLTerm[] entries */
 143   /**** whereLoopXfer() copies fields above ***********************/
 144 # define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
 145   u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
 146   WhereTerm **aLTerm;   /* WhereTerms used */
 147   WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
 148   WhereTerm *aLTermSpace[3];  /* Initial aLTerm[] space */
 149 };
 150
 151 /* This object holds the prerequisites and the cost of running a
 152 ** subquery on one operand of an OR operator in the WHERE clause.
 153 ** See WhereOrSet for additional information
 154 */
 155 struct WhereOrCost {
 156   Bitmask prereq;     /* Prerequisites */
 157   LogEst rRun;        /* Cost of running this subquery */
 158   LogEst nOut;        /* Number of outputs for this subquery */
 159 };
 160
 161 /* The WhereOrSet object holds a set of possible WhereOrCosts that
 162 ** correspond to the subquery(s) of OR-clause processing.  Only the
 163 ** best N_OR_COST elements are retained.
 164 */
 165 #define N_OR_COST 3
 166 struct WhereOrSet {
 167   u16 n;                      /* Number of valid a[] entries */
 168   WhereOrCost a[N_OR_COST];   /* Set of best costs */
 169 };
 170
 171 /*
 172 ** Each instance of this object holds a sequence of WhereLoop objects
 173 ** that implement some or all of a query plan.
 174 **
 175 ** Think of each WhereLoop object as a node in a graph with arcs
 176 ** showing dependencies and costs for travelling between nodes.  (That is
 177 ** not a completely accurate description because WhereLoop costs are a
 178 ** vector, not a scalar, and because dependencies are many-to-one, not
 179 ** one-to-one as are graph nodes.  But it is a useful visualization aid.)
 180 ** Then a WherePath object is a path through the graph that visits some
 181 ** or all of the WhereLoop objects once.
 182 **
 183 ** The "solver" works by creating the N best WherePath objects of length
 184 ** 1.  Then using those as a basis to compute the N best WherePath objects
 185 ** of length 2.  And so forth until the length of WherePaths equals the
 186 ** number of nodes in the FROM clause.  The best (lowest cost) WherePath
 187 ** at the end is the chosen query plan.
 188 */
 189 struct WherePath {
 190   Bitmask maskLoop;     /* Bitmask of all WhereLoop objects in this path */
 191   Bitmask revLoop;      /* aLoop[]s that should be reversed for ORDER BY */
 192   LogEst nRow;          /* Estimated number of rows generated by this path */
 193   LogEst rCost;         /* Total cost of this path */
 194   LogEst rUnsorted;     /* Total cost of this path ignoring sorting costs */
 195   i8 isOrdered;         /* No. of ORDER BY terms satisfied. -1 for unknown */
 196   WhereLoop **aLoop;    /* Array of WhereLoop objects implementing this path */
 197 };
 198
 199 /*
 200 ** The query generator uses an array of instances of this structure to
 201 ** help it analyze the subexpressions of the WHERE clause.  Each WHERE
 202 ** clause subexpression is separated from the others by AND operators,
 203 ** usually, or sometimes subexpressions separated by OR.
 204 **
 205 ** All WhereTerms are collected into a single WhereClause structure.
 206 ** The following identity holds:
 207 **
 208 **        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
 209 **
 210 ** When a term is of the form:
 211 **
 212 **              X <op> <expr>
 213 **
 214 ** where X is a column name and <op> is one of certain operators,
 215 ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
 216 ** cursor number and column number for X.  WhereTerm.eOperator records
 217 ** the <op> using a bitmask encoding defined by WO_xxx below.  The
 218 ** use of a bitmask encoding for the operator allows us to search
 219 ** quickly for terms that match any of several different operators.
 220 **
 221 ** A WhereTerm might also be two or more subterms connected by OR:
 222 **
 223 **         (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
 224 **
 225 ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR
 226 ** and the WhereTerm.u.pOrInfo field points to auxiliary information that
 227 ** is collected about the OR clause.
 228 **
 229 ** If a term in the WHERE clause does not match either of the two previous
 230 ** categories, then eOperator==0.  The WhereTerm.pExpr field is still set
 231 ** to the original subexpression content and wtFlags is set up appropriately
 232 ** but no other fields in the WhereTerm object are meaningful.
 233 **
 234 ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
 235 ** but they do so indirectly.  A single WhereMaskSet structure translates
 236 ** cursor number into bits and the translated bit is stored in the prereq
 237 ** fields.  The translation is used in order to maximize the number of
 238 ** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
 239 ** spread out over the non-negative integers.  For example, the cursor
 240 ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The WhereMaskSet
 241 ** translates these sparse cursor numbers into consecutive integers
 242 ** beginning with 0 in order to make the best possible use of the available
 243 ** bits in the Bitmask.  So, in the example above, the cursor numbers
 244 ** would be mapped into integers 0 through 7.
 245 **
 246 ** The number of terms in a join is limited by the number of bits
 247 ** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
 248 ** is only able to process joins with 64 or fewer tables.
 249 */
 250 struct WhereTerm {
 251   Expr *pExpr;            /* Pointer to the subexpression that is this term */
 252   WhereClause *pWC;       /* The clause this term is part of */
 253   LogEst truthProb;       /* Probability of truth for this expression */
 254   u16 wtFlags;            /* TERM_xxx bit flags.  See below */
 255   u16 eOperator;          /* A WO_xx value describing <op> */
 256   u8 nChild;              /* Number of children that must disable us */
 257   u8 eMatchOp;            /* Op for vtab MATCH/LIKE/GLOB/REGEXP terms */
 258   int iParent;            /* Disable pWC->a[iParent] when this term disabled */
 259   int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
 260   int iField;             /* Field in (?,?,?) IN (SELECT...) vector */
 261   union {
 262     int leftColumn;         /* Column number of X in "X <op> <expr>" */
 263     WhereOrInfo *pOrInfo;   /* Extra information if (eOperator & WO_OR)!=0 */
 264     WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */
 265   } u;
 266   Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
 267   Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
 268 };
 269
 270 /*
 271 ** Allowed values of WhereTerm.wtFlags
 272 */
 273 #define TERM_DYNAMIC    0x01   /* Need to call sqlite3ExprDelete(db, pExpr) */
 274 #define TERM_VIRTUAL    0x02   /* Added by the optimizer.  Do not code */
 275 #define TERM_CODED      0x04   /* This term is already coded */
 276 #define TERM_COPIED     0x08   /* Has a child */
 277 #define TERM_ORINFO     0x10   /* Need to free the WhereTerm.u.pOrInfo object */
 278 #define TERM_ANDINFO    0x20   /* Need to free the WhereTerm.u.pAndInfo obj */
 279 #define TERM_OR_OK      0x40   /* Used during OR-clause processing */
 280 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
 281 #  define TERM_VNULL    0x80   /* Manufactured x>NULL or x<=NULL term */
 282 #else
 283 #  define TERM_VNULL    0x00   /* Disabled if not using stat3 */
 284 #endif
 285 #define TERM_LIKEOPT    0x100  /* Virtual terms from the LIKE optimization */
 286 #define TERM_LIKECOND   0x200  /* Conditionally this LIKE operator term */
 287 #define TERM_LIKE       0x400  /* The original LIKE operator */
 288 #define TERM_IS         0x800  /* Term.pExpr is an IS operator */
 289 #define TERM_VARSELECT  0x1000 /* Term.pExpr contains a correlated sub-query */
 290
 291 /*
 292 ** An instance of the WhereScan object is used as an iterator for locating
 293 ** terms in the WHERE clause that are useful to the query planner.
 294 */
 295 struct WhereScan {
 296   WhereClause *pOrigWC;      /* Original, innermost WhereClause */
 297   WhereClause *pWC;          /* WhereClause currently being scanned */
 298   const char *zCollName;     /* Required collating sequence, if not NULL */
 299   Expr *pIdxExpr;            /* Search for this index expression */
 300   char idxaff;               /* Must match this affinity, if zCollName!=NULL */
 301   unsigned char nEquiv;      /* Number of entries in aEquiv[] */
 302   unsigned char iEquiv;      /* Next unused slot in aEquiv[] */
 303   u32 opMask;                /* Acceptable operators */
 304   int k;                     /* Resume scanning at this->pWC->a[this->k] */
 305   int aiCur[11];             /* Cursors in the equivalence class */
 306   i16 aiColumn[11];          /* Corresponding column number in the eq-class */
 307 };
 308
 309 /*
 310 ** An instance of the following structure holds all information about a
 311 ** WHERE clause.  Mostly this is a container for one or more WhereTerms.
 312 **
 313 ** Explanation of pOuter:  For a WHERE clause of the form
 314 **
 315 **           a AND ((b AND c) OR (d AND e)) AND f
 316 **
 317 ** There are separate WhereClause objects for the whole clause and for
 318 ** the subclauses "(b AND c)" and "(d AND e)".  The pOuter field of the
 319 ** subclauses points to the WhereClause object for the whole clause.
 320 */
 321 struct WhereClause {
 322   WhereInfo *pWInfo;       /* WHERE clause processing context */
 323   WhereClause *pOuter;     /* Outer conjunction */
 324   u8 op;                   /* Split operator.  TK_AND or TK_OR */
 325   int nTerm;               /* Number of terms */
 326   int nSlot;               /* Number of entries in a[] */
 327   WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
 328 #if defined(SQLITE_SMALL_STACK)
 329   WhereTerm aStatic[1];    /* Initial static space for a[] */
 330 #else
 331   WhereTerm aStatic[8];    /* Initial static space for a[] */
 332 #endif
 333 };
 334
 335 /*
 336 ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
 337 ** a dynamically allocated instance of the following structure.
 338 */
 339 struct WhereOrInfo {
 340   WhereClause wc;          /* Decomposition into subterms */
 341   Bitmask indexable;       /* Bitmask of all indexable tables in the clause */
 342 };
 343
 344 /*
 345 ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
 346 ** a dynamically allocated instance of the following structure.
 347 */
 348 struct WhereAndInfo {
 349   WhereClause wc;          /* The subexpression broken out */
 350 };
 351
 352 /*
 353 ** An instance of the following structure keeps track of a mapping
 354 ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
 355 **
 356 ** The VDBE cursor numbers are small integers contained in
 357 ** SrcList_item.iCursor and Expr.iTable fields.  For any given WHERE
 358 ** clause, the cursor numbers might not begin with 0 and they might
 359 ** contain gaps in the numbering sequence.  But we want to make maximum
 360 ** use of the bits in our bitmasks.  This structure provides a mapping
 361 ** from the sparse cursor numbers into consecutive integers beginning
 362 ** with 0.
 363 **
 364 ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
 365 ** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
 366 **
 367 ** For example, if the WHERE clause expression used these VDBE
 368 ** cursors:  4, 5, 8, 29, 57, 73.  Then the  WhereMaskSet structure
 369 ** would map those cursor numbers into bits 0 through 5.
 370 **
 371 ** Note that the mapping is not necessarily ordered.  In the example
 372 ** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
 373 ** 57->5, 73->4.  Or one of 719 other combinations might be used. It
 374 ** does not really matter.  What is important is that sparse cursor
 375 ** numbers all get mapped into bit numbers that begin with 0 and contain
 376 ** no gaps.
 377 */
 378 struct WhereMaskSet {
 379   int bVarSelect;               /* Used by sqlite3WhereExprUsage() */
 380   int n;                        /* Number of assigned cursor values */
 381   int ix[BMS];                  /* Cursor assigned to each bit */
 382 };
 383
 384 /*
 385 ** Initialize a WhereMaskSet object
 386 */
 387 #define initMaskSet(P)  (P)->n=0
 388
 389 /*
 390 ** This object is a convenience wrapper holding all information needed
 391 ** to construct WhereLoop objects for a particular query.
 392 */
 393 struct WhereLoopBuilder {
 394   WhereInfo *pWInfo;        /* Information about this WHERE */
 395   WhereClause *pWC;         /* WHERE clause terms */
 396   ExprList *pOrderBy;       /* ORDER BY clause */
 397   WhereLoop *pNew;          /* Template WhereLoop */
 398   WhereOrSet *pOrSet;       /* Record best loops here, if not NULL */
 399 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
 400   UnpackedRecord *pRec;     /* Probe for stat4 (if required) */
 401   int nRecValid;            /* Number of valid fields currently in pRec */
 402 #endif
 403   unsigned int bldFlags;    /* SQLITE_BLDF_* flags */
 404 };
 405
 406 /* Allowed values for WhereLoopBuider.bldFlags */
 407 #define SQLITE_BLDF_INDEXED  0x0001   /* An index is used */
 408 #define SQLITE_BLDF_UNIQUE   0x0002   /* All keys of a UNIQUE index used */
 409
 410 /*
 411 ** The WHERE clause processing routine has two halves.  The
 412 ** first part does the start of the WHERE loop and the second
 413 ** half does the tail of the WHERE loop.  An instance of
 414 ** this structure is returned by the first half and passed
 415 ** into the second half to give some continuity.
 416 **
 417 ** An instance of this object holds the complete state of the query
 418 ** planner.
 419 */
 420 struct WhereInfo {
 421   Parse *pParse;            /* Parsing and code generating context */
 422   SrcList *pTabList;        /* List of tables in the join */
 423   ExprList *pOrderBy;       /* The ORDER BY clause or NULL */
 424   ExprList *pResultSet;     /* Result set of the query */
 425   Expr *pWhere;             /* The complete WHERE clause */
 426   LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
 427   int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
 428   int iContinue;            /* Jump here to continue with next record */
 429   int iBreak;               /* Jump here to break out of the loop */
 430   int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
 431   u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
 432   u8 nLevel;                /* Number of nested loop */
 433   i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
 434   u8 sorted;                /* True if really sorted (not just grouped) */
 435   u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
 436   u8 untestedTerms;         /* Not all WHERE terms resolved by outer loop */
 437   u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
 438   u8 bOrderedInnerLoop;     /* True if only the inner-most loop is ordered */
 439   int iTop;                 /* The very beginning of the WHERE loop */
 440   WhereLoop *pLoops;        /* List of all WhereLoop objects */
 441   Bitmask revMask;          /* Mask of ORDER BY terms that need reversing */
 442   LogEst nRowOut;           /* Estimated number of output rows */
 443   WhereClause sWC;          /* Decomposition of the WHERE clause */
 444   WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
 445   WhereLevel a[1];          /* Information about each nest loop in WHERE */
 446 };
 447
 448 /*
 449 ** Private interfaces - callable only by other where.c routines.
 450 **
 451 ** where.c:
 452 */
 453 Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
 454 #ifdef WHERETRACE_ENABLED
 455 void sqlite3WhereClausePrint(WhereClause *pWC);
 456 #endif
 457 WhereTerm *sqlite3WhereFindTerm(
 458   WhereClause *pWC,     /* The WHERE clause to be searched */
 459   int iCur,             /* Cursor number of LHS */
 460   int iColumn,          /* Column number of LHS */
 461   Bitmask notReady,     /* RHS must not overlap with this mask */
 462   u32 op,               /* Mask of WO_xx values describing operator */
 463   Index *pIdx           /* Must be compatible with this index, if not NULL */
 464 );
 465
 466 /* wherecode.c: */
 467 #ifndef SQLITE_OMIT_EXPLAIN
 468 int sqlite3WhereExplainOneScan(
 469   Parse *pParse,                  /* Parse context */
 470   SrcList *pTabList,              /* Table list this loop refers to */
 471   WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
 472   u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
 473 );
 474 #else
 475 # define sqlite3WhereExplainOneScan(u,v,w,x) 0
 476 #endif /* SQLITE_OMIT_EXPLAIN */
 477 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
 478 void sqlite3WhereAddScanStatus(
 479   Vdbe *v,                        /* Vdbe to add scanstatus entry to */
 480   SrcList *pSrclist,              /* FROM clause pLvl reads data from */
 481   WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
 482   int addrExplain                 /* Address of OP_Explain (or 0) */
 483 );
 484 #else
 485 # define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
 486 #endif
 487 Bitmask sqlite3WhereCodeOneLoopStart(
 488   WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
 489   int iLevel,          /* Which level of pWInfo->a[] should be coded */
 490   Bitmask notReady     /* Which tables are currently available */
 491 );
 492
 493 /* whereexpr.c: */
 494 void sqlite3WhereClauseInit(WhereClause*,WhereInfo*);
 495 void sqlite3WhereClauseClear(WhereClause*);
 496 void sqlite3WhereSplit(WhereClause*,Expr*,u8);
 497 Bitmask sqlite3WhereExprUsage(WhereMaskSet*, Expr*);
 498 Bitmask sqlite3WhereExprListUsage(WhereMaskSet*, ExprList*);
 499 void sqlite3WhereExprAnalyze(SrcList*, WhereClause*);
 500 void sqlite3WhereTabFuncArgs(Parse*, struct SrcList_item*, WhereClause*);
 501
 502
 503
 504
 505
 506 /*
 507 ** Bitmasks for the operators on WhereTerm objects.  These are all
 508 ** operators that are of interest to the query planner.  An
 509 ** OR-ed combination of these values can be used when searching for
 510 ** particular WhereTerms within a WhereClause.
 511 **
 512 ** Value constraints:
 513 **     WO_EQ    == SQLITE_INDEX_CONSTRAINT_EQ
 514 **     WO_LT    == SQLITE_INDEX_CONSTRAINT_LT
 515 **     WO_LE    == SQLITE_INDEX_CONSTRAINT_LE
 516 **     WO_GT    == SQLITE_INDEX_CONSTRAINT_GT
 517 **     WO_GE    == SQLITE_INDEX_CONSTRAINT_GE
 518 */
 519 #define WO_IN     0x0001
 520 #define WO_EQ     0x0002
 521 #define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
 522 #define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
 523 #define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
 524 #define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
 525 #define WO_AUX    0x0040       /* Op useful to virtual tables only */
 526 #define WO_IS     0x0080
 527 #define WO_ISNULL 0x0100
 528 #define WO_OR     0x0200       /* Two or more OR-connected terms */
 529 #define WO_AND    0x0400       /* Two or more AND-connected terms */
 530 #define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
 531 #define WO_NOOP   0x1000       /* This term does not restrict search space */
 532
 533 #define WO_ALL    0x1fff       /* Mask of all possible WO_* values */
 534 #define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */
 535
 536 /*
 537 ** These are definitions of bits in the WhereLoop.wsFlags field.
 538 ** The particular combination of bits in each WhereLoop help to
 539 ** determine the algorithm that WhereLoop represents.
 540 */
 541 #define WHERE_COLUMN_EQ    0x00000001  /* x=EXPR */
 542 #define WHERE_COLUMN_RANGE 0x00000002  /* x<EXPR and/or x>EXPR */
 543 #define WHERE_COLUMN_IN    0x00000004  /* x IN (...) */
 544 #define WHERE_COLUMN_NULL  0x00000008  /* x IS NULL */
 545 #define WHERE_CONSTRAINT   0x0000000f  /* Any of the WHERE_COLUMN_xxx values */
 546 #define WHERE_TOP_LIMIT    0x00000010  /* x<EXPR or x<=EXPR constraint */
 547 #define WHERE_BTM_LIMIT    0x00000020  /* x>EXPR or x>=EXPR constraint */
 548 #define WHERE_BOTH_LIMIT   0x00000030  /* Both x>EXPR and x<EXPR */
 549 #define WHERE_IDX_ONLY     0x00000040  /* Use index only - omit table */
 550 #define WHERE_IPK          0x00000100  /* x is the INTEGER PRIMARY KEY */
 551 #define WHERE_INDEXED      0x00000200  /* WhereLoop.u.btree.pIndex is valid */
 552 #define WHERE_VIRTUALTABLE 0x00000400  /* WhereLoop.u.vtab is valid */
 553 #define WHERE_IN_ABLE      0x00000800  /* Able to support an IN operator */
 554 #define WHERE_ONEROW       0x00001000  /* Selects no more than one row */
 555 #define WHERE_MULTI_OR     0x00002000  /* OR using multiple indices */
 556 #define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
 557 #define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
 558 #define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
 559 #define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
 560 #define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */