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, p3, p5; /* Opcode, P3 & 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 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS 89 int addrVisit; /* Address at which row is visited */ 90 #endif 91 }; 92 93 /* 94 ** Each instance of this object represents an algorithm for evaluating one 95 ** term of a join. Every term of the FROM clause will have at least 96 ** one corresponding WhereLoop object (unless INDEXED BY constraints 97 ** prevent a query solution - which is an error) and many terms of the 98 ** FROM clause will have multiple WhereLoop objects, each describing a 99 ** potential way of implementing that FROM-clause term, together with 100 ** dependencies and cost estimates for using the chosen algorithm. 101 ** 102 ** Query planning consists of building up a collection of these WhereLoop 103 ** objects, then computing a particular sequence of WhereLoop objects, with 104 ** one WhereLoop object per FROM clause term, that satisfy all dependencies 105 ** and that minimize the overall cost. 106 */ 107 struct WhereLoop { 108 Bitmask prereq; /* Bitmask of other loops that must run first */ 109 Bitmask maskSelf; /* Bitmask identifying table iTab */ 110 #ifdef SQLITE_DEBUG 111 char cId; /* Symbolic ID of this loop for debugging use */ 112 #endif 113 u8 iTab; /* Position in FROM clause of table for this loop */ 114 u8 iSortIdx; /* Sorting index number. 0==None */ 115 LogEst rSetup; /* One-time setup cost (ex: create transient index) */ 116 LogEst rRun; /* Cost of running each loop */ 117 LogEst nOut; /* Estimated number of output rows */ 118 union { 119 struct { /* Information for internal btree tables */ 120 u16 nEq; /* Number of equality constraints */ 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 /* Forward declaration of methods */ 164 static int whereLoopResize(sqlite3*, WhereLoop*, int); 165 166 /* 167 ** Each instance of this object holds a sequence of WhereLoop objects 168 ** that implement some or all of a query plan. 169 ** 170 ** Think of each WhereLoop object as a node in a graph with arcs 171 ** showing dependencies and costs for travelling between nodes. (That is 172 ** not a completely accurate description because WhereLoop costs are a 173 ** vector, not a scalar, and because dependencies are many-to-one, not 174 ** one-to-one as are graph nodes. But it is a useful visualization aid.) 175 ** Then a WherePath object is a path through the graph that visits some 176 ** or all of the WhereLoop objects once. 177 ** 178 ** The "solver" works by creating the N best WherePath objects of length 179 ** 1. Then using those as a basis to compute the N best WherePath objects 180 ** of length 2. And so forth until the length of WherePaths equals the 181 ** number of nodes in the FROM clause. The best (lowest cost) WherePath 182 ** at the end is the chosen query plan. 183 */ 184 struct WherePath { 185 Bitmask maskLoop; /* Bitmask of all WhereLoop objects in this path */ 186 Bitmask revLoop; /* aLoop[]s that should be reversed for ORDER BY */ 187 LogEst nRow; /* Estimated number of rows generated by this path */ 188 LogEst rCost; /* Total cost of this path */ 189 LogEst rUnsorted; /* Total cost of this path ignoring sorting costs */ 190 i8 isOrdered; /* No. of ORDER BY terms satisfied. -1 for unknown */ 191 WhereLoop **aLoop; /* Array of WhereLoop objects implementing this path */ 192 }; 193 194 /* 195 ** The query generator uses an array of instances of this structure to 196 ** help it analyze the subexpressions of the WHERE clause. Each WHERE 197 ** clause subexpression is separated from the others by AND operators, 198 ** usually, or sometimes subexpressions separated by OR. 199 ** 200 ** All WhereTerms are collected into a single WhereClause structure. 201 ** The following identity holds: 202 ** 203 ** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm 204 ** 205 ** When a term is of the form: 206 ** 207 ** X <op> <expr> 208 ** 209 ** where X is a column name and <op> is one of certain operators, 210 ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the 211 ** cursor number and column number for X. WhereTerm.eOperator records 212 ** the <op> using a bitmask encoding defined by WO_xxx below. The 213 ** use of a bitmask encoding for the operator allows us to search 214 ** quickly for terms that match any of several different operators. 215 ** 216 ** A WhereTerm might also be two or more subterms connected by OR: 217 ** 218 ** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR .... 219 ** 220 ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR 221 ** and the WhereTerm.u.pOrInfo field points to auxiliary information that 222 ** is collected about the OR clause. 223 ** 224 ** If a term in the WHERE clause does not match either of the two previous 225 ** categories, then eOperator==0. The WhereTerm.pExpr field is still set 226 ** to the original subexpression content and wtFlags is set up appropriately 227 ** but no other fields in the WhereTerm object are meaningful. 228 ** 229 ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers, 230 ** but they do so indirectly. A single WhereMaskSet structure translates 231 ** cursor number into bits and the translated bit is stored in the prereq 232 ** fields. The translation is used in order to maximize the number of 233 ** bits that will fit in a Bitmask. The VDBE cursor numbers might be 234 ** spread out over the non-negative integers. For example, the cursor 235 ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet 236 ** translates these sparse cursor numbers into consecutive integers 237 ** beginning with 0 in order to make the best possible use of the available 238 ** bits in the Bitmask. So, in the example above, the cursor numbers 239 ** would be mapped into integers 0 through 7. 240 ** 241 ** The number of terms in a join is limited by the number of bits 242 ** in prereqRight and prereqAll. The default is 64 bits, hence SQLite 243 ** is only able to process joins with 64 or fewer tables. 244 */ 245 struct WhereTerm { 246 Expr *pExpr; /* Pointer to the subexpression that is this term */ 247 int iParent; /* Disable pWC->a[iParent] when this term disabled */ 248 int leftCursor; /* Cursor number of X in "X <op> <expr>" */ 249 union { 250 int leftColumn; /* Column number of X in "X <op> <expr>" */ 251 WhereOrInfo *pOrInfo; /* Extra information if (eOperator & WO_OR)!=0 */ 252 WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */ 253 } u; 254 LogEst truthProb; /* Probability of truth for this expression */ 255 u16 eOperator; /* A WO_xx value describing <op> */ 256 u8 wtFlags; /* TERM_xxx bit flags. See below */ 257 u8 nChild; /* Number of children that must disable us */ 258 WhereClause *pWC; /* The clause this term is part of */ 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 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */ 267 #define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */ 268 #define TERM_CODED 0x04 /* This term is already coded */ 269 #define TERM_COPIED 0x08 /* Has a child */ 270 #define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */ 271 #define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */ 272 #define TERM_OR_OK 0x40 /* Used during OR-clause processing */ 273 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 274 # define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */ 275 #else 276 # define TERM_VNULL 0x00 /* Disabled if not using stat3 */ 277 #endif 278 279 /* 280 ** An instance of the WhereScan object is used as an iterator for locating 281 ** terms in the WHERE clause that are useful to the query planner. 282 */ 283 struct WhereScan { 284 WhereClause *pOrigWC; /* Original, innermost WhereClause */ 285 WhereClause *pWC; /* WhereClause currently being scanned */ 286 char *zCollName; /* Required collating sequence, if not NULL */ 287 char idxaff; /* Must match this affinity, if zCollName!=NULL */ 288 unsigned char nEquiv; /* Number of entries in aEquiv[] */ 289 unsigned char iEquiv; /* Next unused slot in aEquiv[] */ 290 u32 opMask; /* Acceptable operators */ 291 int k; /* Resume scanning at this->pWC->a[this->k] */ 292 int aEquiv[22]; /* Cursor,Column pairs for equivalence classes */ 293 }; 294 295 /* 296 ** An instance of the following structure holds all information about a 297 ** WHERE clause. Mostly this is a container for one or more WhereTerms. 298 ** 299 ** Explanation of pOuter: For a WHERE clause of the form 300 ** 301 ** a AND ((b AND c) OR (d AND e)) AND f 302 ** 303 ** There are separate WhereClause objects for the whole clause and for 304 ** the subclauses "(b AND c)" and "(d AND e)". The pOuter field of the 305 ** subclauses points to the WhereClause object for the whole clause. 306 */ 307 struct WhereClause { 308 WhereInfo *pWInfo; /* WHERE clause processing context */ 309 WhereClause *pOuter; /* Outer conjunction */ 310 u8 op; /* Split operator. TK_AND or TK_OR */ 311 int nTerm; /* Number of terms */ 312 int nSlot; /* Number of entries in a[] */ 313 WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */ 314 #if defined(SQLITE_SMALL_STACK) 315 WhereTerm aStatic[1]; /* Initial static space for a[] */ 316 #else 317 WhereTerm aStatic[8]; /* Initial static space for a[] */ 318 #endif 319 }; 320 321 /* 322 ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to 323 ** a dynamically allocated instance of the following structure. 324 */ 325 struct WhereOrInfo { 326 WhereClause wc; /* Decomposition into subterms */ 327 Bitmask indexable; /* Bitmask of all indexable tables in the clause */ 328 }; 329 330 /* 331 ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to 332 ** a dynamically allocated instance of the following structure. 333 */ 334 struct WhereAndInfo { 335 WhereClause wc; /* The subexpression broken out */ 336 }; 337 338 /* 339 ** An instance of the following structure keeps track of a mapping 340 ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm. 341 ** 342 ** The VDBE cursor numbers are small integers contained in 343 ** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE 344 ** clause, the cursor numbers might not begin with 0 and they might 345 ** contain gaps in the numbering sequence. But we want to make maximum 346 ** use of the bits in our bitmasks. This structure provides a mapping 347 ** from the sparse cursor numbers into consecutive integers beginning 348 ** with 0. 349 ** 350 ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask 351 ** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A. 352 ** 353 ** For example, if the WHERE clause expression used these VDBE 354 ** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure 355 ** would map those cursor numbers into bits 0 through 5. 356 ** 357 ** Note that the mapping is not necessarily ordered. In the example 358 ** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0, 359 ** 57->5, 73->4. Or one of 719 other combinations might be used. It 360 ** does not really matter. What is important is that sparse cursor 361 ** numbers all get mapped into bit numbers that begin with 0 and contain 362 ** no gaps. 363 */ 364 struct WhereMaskSet { 365 int n; /* Number of assigned cursor values */ 366 int ix[BMS]; /* Cursor assigned to each bit */ 367 }; 368 369 /* 370 ** This object is a convenience wrapper holding all information needed 371 ** to construct WhereLoop objects for a particular query. 372 */ 373 struct WhereLoopBuilder { 374 WhereInfo *pWInfo; /* Information about this WHERE */ 375 WhereClause *pWC; /* WHERE clause terms */ 376 ExprList *pOrderBy; /* ORDER BY clause */ 377 WhereLoop *pNew; /* Template WhereLoop */ 378 WhereOrSet *pOrSet; /* Record best loops here, if not NULL */ 379 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 380 UnpackedRecord *pRec; /* Probe for stat4 (if required) */ 381 int nRecValid; /* Number of valid fields currently in pRec */ 382 #endif 383 }; 384 385 /* 386 ** The WHERE clause processing routine has two halves. The 387 ** first part does the start of the WHERE loop and the second 388 ** half does the tail of the WHERE loop. An instance of 389 ** this structure is returned by the first half and passed 390 ** into the second half to give some continuity. 391 ** 392 ** An instance of this object holds the complete state of the query 393 ** planner. 394 */ 395 struct WhereInfo { 396 Parse *pParse; /* Parsing and code generating context */ 397 SrcList *pTabList; /* List of tables in the join */ 398 ExprList *pOrderBy; /* The ORDER BY clause or NULL */ 399 ExprList *pResultSet; /* Result set. DISTINCT operates on these */ 400 WhereLoop *pLoops; /* List of all WhereLoop objects */ 401 Bitmask revMask; /* Mask of ORDER BY terms that need reversing */ 402 LogEst nRowOut; /* Estimated number of output rows */ 403 u16 wctrlFlags; /* Flags originally passed to sqlite3WhereBegin() */ 404 i8 nOBSat; /* Number of ORDER BY terms satisfied by indices */ 405 u8 sorted; /* True if really sorted (not just grouped) */ 406 u8 okOnePass; /* Ok to use one-pass algorithm for UPDATE/DELETE */ 407 u8 untestedTerms; /* Not all WHERE terms resolved by outer loop */ 408 u8 eDistinct; /* One of the WHERE_DISTINCT_* values below */ 409 u8 nLevel; /* Number of nested loop */ 410 int iTop; /* The very beginning of the WHERE loop */ 411 int iContinue; /* Jump here to continue with next record */ 412 int iBreak; /* Jump here to break out of the loop */ 413 int savedNQueryLoop; /* pParse->nQueryLoop outside the WHERE loop */ 414 int aiCurOnePass[2]; /* OP_OpenWrite cursors for the ONEPASS opt */ 415 WhereMaskSet sMaskSet; /* Map cursor numbers to bitmasks */ 416 WhereClause sWC; /* Decomposition of the WHERE clause */ 417 WhereLevel a[1]; /* Information about each nest loop in WHERE */ 418 }; 419 420 /* 421 ** Bitmasks for the operators on WhereTerm objects. These are all 422 ** operators that are of interest to the query planner. An 423 ** OR-ed combination of these values can be used when searching for 424 ** particular WhereTerms within a WhereClause. 425 */ 426 #define WO_IN 0x001 427 #define WO_EQ 0x002 428 #define WO_LT (WO_EQ<<(TK_LT-TK_EQ)) 429 #define WO_LE (WO_EQ<<(TK_LE-TK_EQ)) 430 #define WO_GT (WO_EQ<<(TK_GT-TK_EQ)) 431 #define WO_GE (WO_EQ<<(TK_GE-TK_EQ)) 432 #define WO_MATCH 0x040 433 #define WO_ISNULL 0x080 434 #define WO_OR 0x100 /* Two or more OR-connected terms */ 435 #define WO_AND 0x200 /* Two or more AND-connected terms */ 436 #define WO_EQUIV 0x400 /* Of the form A==B, both columns */ 437 #define WO_NOOP 0x800 /* This term does not restrict search space */ 438 439 #define WO_ALL 0xfff /* Mask of all possible WO_* values */ 440 #define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */ 441 442 /* 443 ** These are definitions of bits in the WhereLoop.wsFlags field. 444 ** The particular combination of bits in each WhereLoop help to 445 ** determine the algorithm that WhereLoop represents. 446 */ 447 #define WHERE_COLUMN_EQ 0x00000001 /* x=EXPR */ 448 #define WHERE_COLUMN_RANGE 0x00000002 /* x<EXPR and/or x>EXPR */ 449 #define WHERE_COLUMN_IN 0x00000004 /* x IN (...) */ 450 #define WHERE_COLUMN_NULL 0x00000008 /* x IS NULL */ 451 #define WHERE_CONSTRAINT 0x0000000f /* Any of the WHERE_COLUMN_xxx values */ 452 #define WHERE_TOP_LIMIT 0x00000010 /* x<EXPR or x<=EXPR constraint */ 453 #define WHERE_BTM_LIMIT 0x00000020 /* x>EXPR or x>=EXPR constraint */ 454 #define WHERE_BOTH_LIMIT 0x00000030 /* Both x>EXPR and x<EXPR */ 455 #define WHERE_IDX_ONLY 0x00000040 /* Use index only - omit table */ 456 #define WHERE_IPK 0x00000100 /* x is the INTEGER PRIMARY KEY */ 457 #define WHERE_INDEXED 0x00000200 /* WhereLoop.u.btree.pIndex is valid */ 458 #define WHERE_VIRTUALTABLE 0x00000400 /* WhereLoop.u.vtab is valid */ 459 #define WHERE_IN_ABLE 0x00000800 /* Able to support an IN operator */ 460 #define WHERE_ONEROW 0x00001000 /* Selects no more than one row */ 461 #define WHERE_MULTI_OR 0x00002000 /* OR using multiple indices */ 462 #define WHERE_AUTO_INDEX 0x00004000 /* Uses an ephemeral index */ 463 #define WHERE_SKIPSCAN 0x00008000 /* Uses the skip-scan algorithm */ 464 #define WHERE_UNQ_WANTED 0x00010000 /* WHERE_ONEROW would have been helpful*/ 465 #define WHERE_PARTIALIDX 0x00020000 /* The automatic index is partial */ 466