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 /***/ int sqlite3WhereTrace = 0; 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 u8 iFrom; /* Which entry in the FROM clause */ 73 u8 op, p5; /* Opcode and P5 of the opcode that ends the loop */ 74 int p1, p2; /* Operands of the opcode used to ends the loop */ 75 union { /* Information that depends on pWLoop->wsFlags */ 76 struct { 77 int nIn; /* Number of entries in aInLoop[] */ 78 struct InLoop { 79 int iCur; /* The VDBE cursor used by this IN operator */ 80 int addrInTop; /* Top of the IN loop */ 81 u8 eEndLoopOp; /* IN Loop terminator. OP_Next or OP_Prev */ 82 } *aInLoop; /* Information about each nested IN operator */ 83 } in; /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */ 84 Index *pCovidx; /* Possible covering index for WHERE_MULTI_OR */ 85 } u; 86 struct WhereLoop *pWLoop; /* The selected WhereLoop object */ 87 Bitmask notReady; /* FROM entries not usable at this level */ 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 nSkip; /* Number of initial index columns to skip */ 119 Index *pIndex; /* Index used, or NULL */ 120 } btree; 121 struct { /* Information for virtual tables */ 122 int idxNum; /* Index number */ 123 u8 needFree; /* True if sqlite3_free(idxStr) is needed */ 124 u8 isOrdered; /* True if satisfies ORDER BY */ 125 u16 omitMask; /* Terms that may be omitted */ 126 char *idxStr; /* Index identifier string */ 127 } vtab; 128 } u; 129 u32 wsFlags; /* WHERE_* flags describing the plan */ 130 u16 nLTerm; /* Number of entries in aLTerm[] */ 131 /**** whereLoopXfer() copies fields above ***********************/ 132 # define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot) 133 u16 nLSlot; /* Number of slots allocated for aLTerm[] */ 134 WhereTerm **aLTerm; /* WhereTerms used */ 135 WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */ 136 WhereTerm *aLTermSpace[4]; /* Initial aLTerm[] space */ 137 }; 138 139 /* This object holds the prerequisites and the cost of running a 140 ** subquery on one operand of an OR operator in the WHERE clause. 141 ** See WhereOrSet for additional information 142 */ 143 struct WhereOrCost { 144 Bitmask prereq; /* Prerequisites */ 145 LogEst rRun; /* Cost of running this subquery */ 146 LogEst nOut; /* Number of outputs for this subquery */ 147 }; 148 149 /* The WhereOrSet object holds a set of possible WhereOrCosts that 150 ** correspond to the subquery(s) of OR-clause processing. Only the 151 ** best N_OR_COST elements are retained. 152 */ 153 #define N_OR_COST 3 154 struct WhereOrSet { 155 u16 n; /* Number of valid a[] entries */ 156 WhereOrCost a[N_OR_COST]; /* Set of best costs */ 157 }; 158 159 160 /* Forward declaration of methods */ 161 static int whereLoopResize(sqlite3*, WhereLoop*, int); 162 163 /* 164 ** Each instance of this object holds a sequence of WhereLoop objects 165 ** that implement some or all of a query plan. 166 ** 167 ** Think of each WhereLoop object as a node in a graph with arcs 168 ** showing dependencies and costs for travelling between nodes. (That is 169 ** not a completely accurate description because WhereLoop costs are a 170 ** vector, not a scalar, and because dependencies are many-to-one, not 171 ** one-to-one as are graph nodes. But it is a useful visualization aid.) 172 ** Then a WherePath object is a path through the graph that visits some 173 ** or all of the WhereLoop objects once. 174 ** 175 ** The "solver" works by creating the N best WherePath objects of length 176 ** 1. Then using those as a basis to compute the N best WherePath objects 177 ** of length 2. And so forth until the length of WherePaths equals the 178 ** number of nodes in the FROM clause. The best (lowest cost) WherePath 179 ** at the end is the choosen query plan. 180 */ 181 struct WherePath { 182 Bitmask maskLoop; /* Bitmask of all WhereLoop objects in this path */ 183 Bitmask revLoop; /* aLoop[]s that should be reversed for ORDER BY */ 184 LogEst nRow; /* Estimated number of rows generated by this path */ 185 LogEst rCost; /* Total cost of this path */ 186 u8 isOrdered; /* True if this path satisfies ORDER BY */ 187 u8 isOrderedValid; /* True if the isOrdered field is valid */ 188 WhereLoop **aLoop; /* Array of WhereLoop objects implementing this path */ 189 }; 190 191 /* 192 ** The query generator uses an array of instances of this structure to 193 ** help it analyze the subexpressions of the WHERE clause. Each WHERE 194 ** clause subexpression is separated from the others by AND operators, 195 ** usually, or sometimes subexpressions separated by OR. 196 ** 197 ** All WhereTerms are collected into a single WhereClause structure. 198 ** The following identity holds: 199 ** 200 ** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm 201 ** 202 ** When a term is of the form: 203 ** 204 ** X <op> <expr> 205 ** 206 ** where X is a column name and <op> is one of certain operators, 207 ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the 208 ** cursor number and column number for X. WhereTerm.eOperator records 209 ** the <op> using a bitmask encoding defined by WO_xxx below. The 210 ** use of a bitmask encoding for the operator allows us to search 211 ** quickly for terms that match any of several different operators. 212 ** 213 ** A WhereTerm might also be two or more subterms connected by OR: 214 ** 215 ** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR .... 216 ** 217 ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR 218 ** and the WhereTerm.u.pOrInfo field points to auxiliary information that 219 ** is collected about the OR clause. 220 ** 221 ** If a term in the WHERE clause does not match either of the two previous 222 ** categories, then eOperator==0. The WhereTerm.pExpr field is still set 223 ** to the original subexpression content and wtFlags is set up appropriately 224 ** but no other fields in the WhereTerm object are meaningful. 225 ** 226 ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers, 227 ** but they do so indirectly. A single WhereMaskSet structure translates 228 ** cursor number into bits and the translated bit is stored in the prereq 229 ** fields. The translation is used in order to maximize the number of 230 ** bits that will fit in a Bitmask. The VDBE cursor numbers might be 231 ** spread out over the non-negative integers. For example, the cursor 232 ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet 233 ** translates these sparse cursor numbers into consecutive integers 234 ** beginning with 0 in order to make the best possible use of the available 235 ** bits in the Bitmask. So, in the example above, the cursor numbers 236 ** would be mapped into integers 0 through 7. 237 ** 238 ** The number of terms in a join is limited by the number of bits 239 ** in prereqRight and prereqAll. The default is 64 bits, hence SQLite 240 ** is only able to process joins with 64 or fewer tables. 241 */ 242 struct WhereTerm { 243 Expr *pExpr; /* Pointer to the subexpression that is this term */ 244 int iParent; /* Disable pWC->a[iParent] when this term disabled */ 245 int leftCursor; /* Cursor number of X in "X <op> <expr>" */ 246 union { 247 int leftColumn; /* Column number of X in "X <op> <expr>" */ 248 WhereOrInfo *pOrInfo; /* Extra information if (eOperator & WO_OR)!=0 */ 249 WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */ 250 } u; 251 LogEst truthProb; /* Probability of truth for this expression */ 252 u16 eOperator; /* A WO_xx value describing <op> */ 253 u8 wtFlags; /* TERM_xxx bit flags. See below */ 254 u8 nChild; /* Number of children that must disable us */ 255 WhereClause *pWC; /* The clause this term is part of */ 256 Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */ 257 Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */ 258 }; 259 260 /* 261 ** Allowed values of WhereTerm.wtFlags 262 */ 263 #define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */ 264 #define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */ 265 #define TERM_CODED 0x04 /* This term is already coded */ 266 #define TERM_COPIED 0x08 /* Has a child */ 267 #define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */ 268 #define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */ 269 #define TERM_OR_OK 0x40 /* Used during OR-clause processing */ 270 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 271 # define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */ 272 #else 273 # define TERM_VNULL 0x00 /* Disabled if not using stat3 */ 274 #endif 275 276 /* 277 ** An instance of the WhereScan object is used as an iterator for locating 278 ** terms in the WHERE clause that are useful to the query planner. 279 */ 280 struct WhereScan { 281 WhereClause *pOrigWC; /* Original, innermost WhereClause */ 282 WhereClause *pWC; /* WhereClause currently being scanned */ 283 char *zCollName; /* Required collating sequence, if not NULL */ 284 char idxaff; /* Must match this affinity, if zCollName!=NULL */ 285 unsigned char nEquiv; /* Number of entries in aEquiv[] */ 286 unsigned char iEquiv; /* Next unused slot in aEquiv[] */ 287 u32 opMask; /* Acceptable operators */ 288 int k; /* Resume scanning at this->pWC->a[this->k] */ 289 int aEquiv[22]; /* Cursor,Column pairs for equivalence classes */ 290 }; 291 292 /* 293 ** An instance of the following structure holds all information about a 294 ** WHERE clause. Mostly this is a container for one or more WhereTerms. 295 ** 296 ** Explanation of pOuter: For a WHERE clause of the form 297 ** 298 ** a AND ((b AND c) OR (d AND e)) AND f 299 ** 300 ** There are separate WhereClause objects for the whole clause and for 301 ** the subclauses "(b AND c)" and "(d AND e)". The pOuter field of the 302 ** subclauses points to the WhereClause object for the whole clause. 303 */ 304 struct WhereClause { 305 WhereInfo *pWInfo; /* WHERE clause processing context */ 306 WhereClause *pOuter; /* Outer conjunction */ 307 u8 op; /* Split operator. TK_AND or TK_OR */ 308 int nTerm; /* Number of terms */ 309 int nSlot; /* Number of entries in a[] */ 310 WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */ 311 #if defined(SQLITE_SMALL_STACK) 312 WhereTerm aStatic[1]; /* Initial static space for a[] */ 313 #else 314 WhereTerm aStatic[8]; /* Initial static space for a[] */ 315 #endif 316 }; 317 318 /* 319 ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to 320 ** a dynamically allocated instance of the following structure. 321 */ 322 struct WhereOrInfo { 323 WhereClause wc; /* Decomposition into subterms */ 324 Bitmask indexable; /* Bitmask of all indexable tables in the clause */ 325 }; 326 327 /* 328 ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to 329 ** a dynamically allocated instance of the following structure. 330 */ 331 struct WhereAndInfo { 332 WhereClause wc; /* The subexpression broken out */ 333 }; 334 335 /* 336 ** An instance of the following structure keeps track of a mapping 337 ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm. 338 ** 339 ** The VDBE cursor numbers are small integers contained in 340 ** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE 341 ** clause, the cursor numbers might not begin with 0 and they might 342 ** contain gaps in the numbering sequence. But we want to make maximum 343 ** use of the bits in our bitmasks. This structure provides a mapping 344 ** from the sparse cursor numbers into consecutive integers beginning 345 ** with 0. 346 ** 347 ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask 348 ** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A. 349 ** 350 ** For example, if the WHERE clause expression used these VDBE 351 ** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure 352 ** would map those cursor numbers into bits 0 through 5. 353 ** 354 ** Note that the mapping is not necessarily ordered. In the example 355 ** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0, 356 ** 57->5, 73->4. Or one of 719 other combinations might be used. It 357 ** does not really matter. What is important is that sparse cursor 358 ** numbers all get mapped into bit numbers that begin with 0 and contain 359 ** no gaps. 360 */ 361 struct WhereMaskSet { 362 int n; /* Number of assigned cursor values */ 363 int ix[BMS]; /* Cursor assigned to each bit */ 364 }; 365 366 /* 367 ** This object is a convenience wrapper holding all information needed 368 ** to construct WhereLoop objects for a particular query. 369 */ 370 struct WhereLoopBuilder { 371 WhereInfo *pWInfo; /* Information about this WHERE */ 372 WhereClause *pWC; /* WHERE clause terms */ 373 ExprList *pOrderBy; /* ORDER BY clause */ 374 WhereLoop *pNew; /* Template WhereLoop */ 375 WhereOrSet *pOrSet; /* Record best loops here, if not NULL */ 376 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 377 UnpackedRecord *pRec; /* Probe for stat4 (if required) */ 378 int nRecValid; /* Number of valid fields currently in pRec */ 379 #endif 380 }; 381 382 /* 383 ** The WHERE clause processing routine has two halves. The 384 ** first part does the start of the WHERE loop and the second 385 ** half does the tail of the WHERE loop. An instance of 386 ** this structure is returned by the first half and passed 387 ** into the second half to give some continuity. 388 ** 389 ** An instance of this object holds the complete state of the query 390 ** planner. 391 */ 392 struct WhereInfo { 393 Parse *pParse; /* Parsing and code generating context */ 394 SrcList *pTabList; /* List of tables in the join */ 395 ExprList *pOrderBy; /* The ORDER BY clause or NULL */ 396 ExprList *pResultSet; /* Result set. DISTINCT operates on these */ 397 WhereLoop *pLoops; /* List of all WhereLoop objects */ 398 Bitmask revMask; /* Mask of ORDER BY terms that need reversing */ 399 LogEst nRowOut; /* Estimated number of output rows */ 400 u16 wctrlFlags; /* Flags originally passed to sqlite3WhereBegin() */ 401 u8 bOBSat; /* ORDER BY satisfied by indices */ 402 u8 okOnePass; /* Ok to use one-pass algorithm for UPDATE/DELETE */ 403 u8 untestedTerms; /* Not all WHERE terms resolved by outer loop */ 404 u8 eDistinct; /* One of the WHERE_DISTINCT_* values below */ 405 u8 nLevel; /* Number of nested loop */ 406 int iTop; /* The very beginning of the WHERE loop */ 407 int iContinue; /* Jump here to continue with next record */ 408 int iBreak; /* Jump here to break out of the loop */ 409 int savedNQueryLoop; /* pParse->nQueryLoop outside the WHERE loop */ 410 int aiCurOnePass[2]; /* OP_OpenWrite cursors for the ONEPASS opt */ 411 WhereMaskSet sMaskSet; /* Map cursor numbers to bitmasks */ 412 WhereClause sWC; /* Decomposition of the WHERE clause */ 413 WhereLevel a[1]; /* Information about each nest loop in WHERE */ 414 }; 415 416 /* 417 ** Bitmasks for the operators on WhereTerm objects. These are all 418 ** operators that are of interest to the query planner. An 419 ** OR-ed combination of these values can be used when searching for 420 ** particular WhereTerms within a WhereClause. 421 */ 422 #define WO_IN 0x001 423 #define WO_EQ 0x002 424 #define WO_LT (WO_EQ<<(TK_LT-TK_EQ)) 425 #define WO_LE (WO_EQ<<(TK_LE-TK_EQ)) 426 #define WO_GT (WO_EQ<<(TK_GT-TK_EQ)) 427 #define WO_GE (WO_EQ<<(TK_GE-TK_EQ)) 428 #define WO_MATCH 0x040 429 #define WO_ISNULL 0x080 430 #define WO_OR 0x100 /* Two or more OR-connected terms */ 431 #define WO_AND 0x200 /* Two or more AND-connected terms */ 432 #define WO_EQUIV 0x400 /* Of the form A==B, both columns */ 433 #define WO_NOOP 0x800 /* This term does not restrict search space */ 434 435 #define WO_ALL 0xfff /* Mask of all possible WO_* values */ 436 #define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */ 437 438 /* 439 ** These are definitions of bits in the WhereLoop.wsFlags field. 440 ** The particular combination of bits in each WhereLoop help to 441 ** determine the algorithm that WhereLoop represents. 442 */ 443 #define WHERE_COLUMN_EQ 0x00000001 /* x=EXPR */ 444 #define WHERE_COLUMN_RANGE 0x00000002 /* x<EXPR and/or x>EXPR */ 445 #define WHERE_COLUMN_IN 0x00000004 /* x IN (...) */ 446 #define WHERE_COLUMN_NULL 0x00000008 /* x IS NULL */ 447 #define WHERE_CONSTRAINT 0x0000000f /* Any of the WHERE_COLUMN_xxx values */ 448 #define WHERE_TOP_LIMIT 0x00000010 /* x<EXPR or x<=EXPR constraint */ 449 #define WHERE_BTM_LIMIT 0x00000020 /* x>EXPR or x>=EXPR constraint */ 450 #define WHERE_BOTH_LIMIT 0x00000030 /* Both x>EXPR and x<EXPR */ 451 #define WHERE_IDX_ONLY 0x00000040 /* Use index only - omit table */ 452 #define WHERE_IPK 0x00000100 /* x is the INTEGER PRIMARY KEY */ 453 #define WHERE_INDEXED 0x00000200 /* WhereLoop.u.btree.pIndex is valid */ 454 #define WHERE_VIRTUALTABLE 0x00000400 /* WhereLoop.u.vtab is valid */ 455 #define WHERE_IN_ABLE 0x00000800 /* Able to support an IN operator */ 456 #define WHERE_ONEROW 0x00001000 /* Selects no more than one row */ 457 #define WHERE_MULTI_OR 0x00002000 /* OR using multiple indices */ 458 #define WHERE_AUTO_INDEX 0x00004000 /* Uses an ephemeral index */ 459 #define WHERE_SKIPSCAN 0x00008000 /* Uses the skip-scan algorithm */ 460