/ Artifact [923820be]

- File src/whereInt.h — part of check-in [299b9570] at 2014-08-08 16:52:28 on branch query-planner-fix — Because SQLite internally calculates query plan costs using a logarithmic scale, very large estimated sorting costs can cause all other estimated costs to be rounded down to zero. In these cases break ties between plans with the same total cost by comparing the costs with sorting excluded. This is an alternative fix for the problem addressed by [2af630c572]. (user: dan size: 21531) [more...]

/* ** 2013-11-12 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** ** This file contains structure and macro definitions for the query ** planner logic in "where.c". These definitions are broken out into ** a separate source file for easier editing. */ /* ** Trace output macros */ #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG) /***/ int sqlite3WhereTrace = 0; #endif #if defined(SQLITE_DEBUG) \ && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE)) # define WHERETRACE(K,X) if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X # define WHERETRACE_ENABLED 1 #else # define WHERETRACE(K,X) #endif /* Forward references */ typedef struct WhereClause WhereClause; typedef struct WhereMaskSet WhereMaskSet; typedef struct WhereOrInfo WhereOrInfo; typedef struct WhereAndInfo WhereAndInfo; typedef struct WhereLevel WhereLevel; typedef struct WhereLoop WhereLoop; typedef struct WherePath WherePath; typedef struct WhereTerm WhereTerm; typedef struct WhereLoopBuilder WhereLoopBuilder; typedef struct WhereScan WhereScan; typedef struct WhereOrCost WhereOrCost; typedef struct WhereOrSet WhereOrSet; /* ** This object contains information needed to implement a single nested ** loop in WHERE clause. ** ** Contrast this object with WhereLoop. This object describes the ** implementation of the loop. WhereLoop describes the algorithm. ** This object contains a pointer to the WhereLoop algorithm as one of ** its elements. ** ** The WhereInfo object contains a single instance of this object for ** each term in the FROM clause (which is to say, for each of the ** nested loops as implemented). The order of WhereLevel objects determines ** the loop nested order, with WhereInfo.a[0] being the outer loop and ** WhereInfo.a[WhereInfo.nLevel-1] being the inner loop. */ struct WhereLevel { int iLeftJoin; /* Memory cell used to implement LEFT OUTER JOIN */ int iTabCur; /* The VDBE cursor used to access the table */ int iIdxCur; /* The VDBE cursor used to access pIdx */ int addrBrk; /* Jump here to break out of the loop */ int addrNxt; /* Jump here to start the next IN combination */ int addrSkip; /* Jump here for next iteration of skip-scan */ int addrCont; /* Jump here to continue with the next loop cycle */ int addrFirst; /* First instruction of interior of the loop */ int addrBody; /* Beginning of the body of this loop */ u8 iFrom; /* Which entry in the FROM clause */ u8 op, p3, p5; /* Opcode, P3 & P5 of the opcode that ends the loop */ int p1, p2; /* Operands of the opcode used to ends the loop */ union { /* Information that depends on pWLoop->wsFlags */ struct { int nIn; /* Number of entries in aInLoop[] */ struct InLoop { int iCur; /* The VDBE cursor used by this IN operator */ int addrInTop; /* Top of the IN loop */ u8 eEndLoopOp; /* IN Loop terminator. OP_Next or OP_Prev */ } *aInLoop; /* Information about each nested IN operator */ } in; /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */ Index *pCovidx; /* Possible covering index for WHERE_MULTI_OR */ } u; struct WhereLoop *pWLoop; /* The selected WhereLoop object */ Bitmask notReady; /* FROM entries not usable at this level */ }; /* ** Each instance of this object represents an algorithm for evaluating one ** term of a join. Every term of the FROM clause will have at least ** one corresponding WhereLoop object (unless INDEXED BY constraints ** prevent a query solution - which is an error) and many terms of the ** FROM clause will have multiple WhereLoop objects, each describing a ** potential way of implementing that FROM-clause term, together with ** dependencies and cost estimates for using the chosen algorithm. ** ** Query planning consists of building up a collection of these WhereLoop ** objects, then computing a particular sequence of WhereLoop objects, with ** one WhereLoop object per FROM clause term, that satisfy all dependencies ** and that minimize the overall cost. */ struct WhereLoop { Bitmask prereq; /* Bitmask of other loops that must run first */ Bitmask maskSelf; /* Bitmask identifying table iTab */ #ifdef SQLITE_DEBUG char cId; /* Symbolic ID of this loop for debugging use */ #endif u8 iTab; /* Position in FROM clause of table for this loop */ u8 iSortIdx; /* Sorting index number. 0==None */ LogEst rSetup; /* One-time setup cost (ex: create transient index) */ LogEst rRun; /* Cost of running each loop */ LogEst nOut; /* Estimated number of output rows */ union { struct { /* Information for internal btree tables */ u16 nEq; /* Number of equality constraints */ u16 nSkip; /* Number of initial index columns to skip */ Index *pIndex; /* Index used, or NULL */ } btree; struct { /* Information for virtual tables */ int idxNum; /* Index number */ u8 needFree; /* True if sqlite3_free(idxStr) is needed */ i8 isOrdered; /* True if satisfies ORDER BY */ u16 omitMask; /* Terms that may be omitted */ char *idxStr; /* Index identifier string */ } vtab; } u; u32 wsFlags; /* WHERE_* flags describing the plan */ u16 nLTerm; /* Number of entries in aLTerm[] */ /**** whereLoopXfer() copies fields above ***********************/ # define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot) u16 nLSlot; /* Number of slots allocated for aLTerm[] */ WhereTerm **aLTerm; /* WhereTerms used */ WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */ WhereTerm *aLTermSpace[4]; /* Initial aLTerm[] space */ }; /* This object holds the prerequisites and the cost of running a ** subquery on one operand of an OR operator in the WHERE clause. ** See WhereOrSet for additional information */ struct WhereOrCost { Bitmask prereq; /* Prerequisites */ LogEst rRun; /* Cost of running this subquery */ LogEst nOut; /* Number of outputs for this subquery */ }; /* The WhereOrSet object holds a set of possible WhereOrCosts that ** correspond to the subquery(s) of OR-clause processing. Only the ** best N_OR_COST elements are retained. */ #define N_OR_COST 3 struct WhereOrSet { u16 n; /* Number of valid a[] entries */ WhereOrCost a[N_OR_COST]; /* Set of best costs */ }; /* Forward declaration of methods */ static int whereLoopResize(sqlite3*, WhereLoop*, int); /* ** Each instance of this object holds a sequence of WhereLoop objects ** that implement some or all of a query plan. ** ** Think of each WhereLoop object as a node in a graph with arcs ** showing dependencies and costs for travelling between nodes. (That is ** not a completely accurate description because WhereLoop costs are a ** vector, not a scalar, and because dependencies are many-to-one, not ** one-to-one as are graph nodes. But it is a useful visualization aid.) ** Then a WherePath object is a path through the graph that visits some ** or all of the WhereLoop objects once. ** ** The "solver" works by creating the N best WherePath objects of length ** 1. Then using those as a basis to compute the N best WherePath objects ** of length 2. And so forth until the length of WherePaths equals the ** number of nodes in the FROM clause. The best (lowest cost) WherePath ** at the end is the choosen query plan. */ struct WherePath { Bitmask maskLoop; /* Bitmask of all WhereLoop objects in this path */ Bitmask revLoop; /* aLoop[]s that should be reversed for ORDER BY */ LogEst nRow; /* Estimated number of rows generated by this path */ LogEst rCost; /* Total cost of this path */ LogEst rUnsorted; /* Total cost of this path ignoring sorting costs */ i8 isOrdered; /* No. of ORDER BY terms satisfied. -1 for unknown */ WhereLoop **aLoop; /* Array of WhereLoop objects implementing this path */ }; /* ** The query generator uses an array of instances of this structure to ** help it analyze the subexpressions of the WHERE clause. Each WHERE ** clause subexpression is separated from the others by AND operators, ** usually, or sometimes subexpressions separated by OR. ** ** All WhereTerms are collected into a single WhereClause structure. ** The following identity holds: ** ** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm ** ** When a term is of the form: ** ** X <op> <expr> ** ** where X is a column name and <op> is one of certain operators, ** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the ** cursor number and column number for X. WhereTerm.eOperator records ** the <op> using a bitmask encoding defined by WO_xxx below. The ** use of a bitmask encoding for the operator allows us to search ** quickly for terms that match any of several different operators. ** ** A WhereTerm might also be two or more subterms connected by OR: ** ** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR .... ** ** In this second case, wtFlag has the TERM_ORINFO bit set and eOperator==WO_OR ** and the WhereTerm.u.pOrInfo field points to auxiliary information that ** is collected about the OR clause. ** ** If a term in the WHERE clause does not match either of the two previous ** categories, then eOperator==0. The WhereTerm.pExpr field is still set ** to the original subexpression content and wtFlags is set up appropriately ** but no other fields in the WhereTerm object are meaningful. ** ** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers, ** but they do so indirectly. A single WhereMaskSet structure translates ** cursor number into bits and the translated bit is stored in the prereq ** fields. The translation is used in order to maximize the number of ** bits that will fit in a Bitmask. The VDBE cursor numbers might be ** spread out over the non-negative integers. For example, the cursor ** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet ** translates these sparse cursor numbers into consecutive integers ** beginning with 0 in order to make the best possible use of the available ** bits in the Bitmask. So, in the example above, the cursor numbers ** would be mapped into integers 0 through 7. ** ** The number of terms in a join is limited by the number of bits ** in prereqRight and prereqAll. The default is 64 bits, hence SQLite ** is only able to process joins with 64 or fewer tables. */ struct WhereTerm { Expr *pExpr; /* Pointer to the subexpression that is this term */ int iParent; /* Disable pWC->a[iParent] when this term disabled */ int leftCursor; /* Cursor number of X in "X <op> <expr>" */ union { int leftColumn; /* Column number of X in "X <op> <expr>" */ WhereOrInfo *pOrInfo; /* Extra information if (eOperator & WO_OR)!=0 */ WhereAndInfo *pAndInfo; /* Extra information if (eOperator& WO_AND)!=0 */ } u; LogEst truthProb; /* Probability of truth for this expression */ u16 eOperator; /* A WO_xx value describing <op> */ u8 wtFlags; /* TERM_xxx bit flags. See below */ u8 nChild; /* Number of children that must disable us */ WhereClause *pWC; /* The clause this term is part of */ Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */ Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */ }; /* ** Allowed values of WhereTerm.wtFlags */ #define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */ #define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */ #define TERM_CODED 0x04 /* This term is already coded */ #define TERM_COPIED 0x08 /* Has a child */ #define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */ #define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */ #define TERM_OR_OK 0x40 /* Used during OR-clause processing */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 # define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */ #else # define TERM_VNULL 0x00 /* Disabled if not using stat3 */ #endif /* ** An instance of the WhereScan object is used as an iterator for locating ** terms in the WHERE clause that are useful to the query planner. */ struct WhereScan { WhereClause *pOrigWC; /* Original, innermost WhereClause */ WhereClause *pWC; /* WhereClause currently being scanned */ char *zCollName; /* Required collating sequence, if not NULL */ char idxaff; /* Must match this affinity, if zCollName!=NULL */ unsigned char nEquiv; /* Number of entries in aEquiv[] */ unsigned char iEquiv; /* Next unused slot in aEquiv[] */ u32 opMask; /* Acceptable operators */ int k; /* Resume scanning at this->pWC->a[this->k] */ int aEquiv[22]; /* Cursor,Column pairs for equivalence classes */ }; /* ** An instance of the following structure holds all information about a ** WHERE clause. Mostly this is a container for one or more WhereTerms. ** ** Explanation of pOuter: For a WHERE clause of the form ** ** a AND ((b AND c) OR (d AND e)) AND f ** ** There are separate WhereClause objects for the whole clause and for ** the subclauses "(b AND c)" and "(d AND e)". The pOuter field of the ** subclauses points to the WhereClause object for the whole clause. */ struct WhereClause { WhereInfo *pWInfo; /* WHERE clause processing context */ WhereClause *pOuter; /* Outer conjunction */ u8 op; /* Split operator. TK_AND or TK_OR */ int nTerm; /* Number of terms */ int nSlot; /* Number of entries in a[] */ WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */ #if defined(SQLITE_SMALL_STACK) WhereTerm aStatic[1]; /* Initial static space for a[] */ #else WhereTerm aStatic[8]; /* Initial static space for a[] */ #endif }; /* ** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to ** a dynamically allocated instance of the following structure. */ struct WhereOrInfo { WhereClause wc; /* Decomposition into subterms */ Bitmask indexable; /* Bitmask of all indexable tables in the clause */ }; /* ** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to ** a dynamically allocated instance of the following structure. */ struct WhereAndInfo { WhereClause wc; /* The subexpression broken out */ }; /* ** An instance of the following structure keeps track of a mapping ** between VDBE cursor numbers and bits of the bitmasks in WhereTerm. ** ** The VDBE cursor numbers are small integers contained in ** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE ** clause, the cursor numbers might not begin with 0 and they might ** contain gaps in the numbering sequence. But we want to make maximum ** use of the bits in our bitmasks. This structure provides a mapping ** from the sparse cursor numbers into consecutive integers beginning ** with 0. ** ** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask ** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A. ** ** For example, if the WHERE clause expression used these VDBE ** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure ** would map those cursor numbers into bits 0 through 5. ** ** Note that the mapping is not necessarily ordered. In the example ** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0, ** 57->5, 73->4. Or one of 719 other combinations might be used. It ** does not really matter. What is important is that sparse cursor ** numbers all get mapped into bit numbers that begin with 0 and contain ** no gaps. */ struct WhereMaskSet { int n; /* Number of assigned cursor values */ int ix[BMS]; /* Cursor assigned to each bit */ }; /* ** This object is a convenience wrapper holding all information needed ** to construct WhereLoop objects for a particular query. */ struct WhereLoopBuilder { WhereInfo *pWInfo; /* Information about this WHERE */ WhereClause *pWC; /* WHERE clause terms */ ExprList *pOrderBy; /* ORDER BY clause */ WhereLoop *pNew; /* Template WhereLoop */ WhereOrSet *pOrSet; /* Record best loops here, if not NULL */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 UnpackedRecord *pRec; /* Probe for stat4 (if required) */ int nRecValid; /* Number of valid fields currently in pRec */ #endif }; /* ** The WHERE clause processing routine has two halves. The ** first part does the start of the WHERE loop and the second ** half does the tail of the WHERE loop. An instance of ** this structure is returned by the first half and passed ** into the second half to give some continuity. ** ** An instance of this object holds the complete state of the query ** planner. */ struct WhereInfo { Parse *pParse; /* Parsing and code generating context */ SrcList *pTabList; /* List of tables in the join */ ExprList *pOrderBy; /* The ORDER BY clause or NULL */ ExprList *pResultSet; /* Result set. DISTINCT operates on these */ WhereLoop *pLoops; /* List of all WhereLoop objects */ Bitmask revMask; /* Mask of ORDER BY terms that need reversing */ LogEst nRowOut; /* Estimated number of output rows */ u16 wctrlFlags; /* Flags originally passed to sqlite3WhereBegin() */ i8 nOBSat; /* Number of ORDER BY terms satisfied by indices */ u8 sorted; /* True if really sorted (not just grouped) */ u8 okOnePass; /* Ok to use one-pass algorithm for UPDATE/DELETE */ u8 untestedTerms; /* Not all WHERE terms resolved by outer loop */ u8 eDistinct; /* One of the WHERE_DISTINCT_* values below */ u8 nLevel; /* Number of nested loop */ int iTop; /* The very beginning of the WHERE loop */ int iContinue; /* Jump here to continue with next record */ int iBreak; /* Jump here to break out of the loop */ int savedNQueryLoop; /* pParse->nQueryLoop outside the WHERE loop */ int aiCurOnePass[2]; /* OP_OpenWrite cursors for the ONEPASS opt */ WhereMaskSet sMaskSet; /* Map cursor numbers to bitmasks */ WhereClause sWC; /* Decomposition of the WHERE clause */ WhereLevel a[1]; /* Information about each nest loop in WHERE */ }; /* ** Bitmasks for the operators on WhereTerm objects. These are all ** operators that are of interest to the query planner. An ** OR-ed combination of these values can be used when searching for ** particular WhereTerms within a WhereClause. */ #define WO_IN 0x001 #define WO_EQ 0x002 #define WO_LT (WO_EQ<<(TK_LT-TK_EQ)) #define WO_LE (WO_EQ<<(TK_LE-TK_EQ)) #define WO_GT (WO_EQ<<(TK_GT-TK_EQ)) #define WO_GE (WO_EQ<<(TK_GE-TK_EQ)) #define WO_MATCH 0x040 #define WO_ISNULL 0x080 #define WO_OR 0x100 /* Two or more OR-connected terms */ #define WO_AND 0x200 /* Two or more AND-connected terms */ #define WO_EQUIV 0x400 /* Of the form A==B, both columns */ #define WO_NOOP 0x800 /* This term does not restrict search space */ #define WO_ALL 0xfff /* Mask of all possible WO_* values */ #define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */ /* ** These are definitions of bits in the WhereLoop.wsFlags field. ** The particular combination of bits in each WhereLoop help to ** determine the algorithm that WhereLoop represents. */ #define WHERE_COLUMN_EQ 0x00000001 /* x=EXPR */ #define WHERE_COLUMN_RANGE 0x00000002 /* x<EXPR and/or x>EXPR */ #define WHERE_COLUMN_IN 0x00000004 /* x IN (...) */ #define WHERE_COLUMN_NULL 0x00000008 /* x IS NULL */ #define WHERE_CONSTRAINT 0x0000000f /* Any of the WHERE_COLUMN_xxx values */ #define WHERE_TOP_LIMIT 0x00000010 /* x<EXPR or x<=EXPR constraint */ #define WHERE_BTM_LIMIT 0x00000020 /* x>EXPR or x>=EXPR constraint */ #define WHERE_BOTH_LIMIT 0x00000030 /* Both x>EXPR and x<EXPR */ #define WHERE_IDX_ONLY 0x00000040 /* Use index only - omit table */ #define WHERE_IPK 0x00000100 /* x is the INTEGER PRIMARY KEY */ #define WHERE_INDEXED 0x00000200 /* WhereLoop.u.btree.pIndex is valid */ #define WHERE_VIRTUALTABLE 0x00000400 /* WhereLoop.u.vtab is valid */ #define WHERE_IN_ABLE 0x00000800 /* Able to support an IN operator */ #define WHERE_ONEROW 0x00001000 /* Selects no more than one row */ #define WHERE_MULTI_OR 0x00002000 /* OR using multiple indices */ #define WHERE_AUTO_INDEX 0x00004000 /* Uses an ephemeral index */ #define WHERE_SKIPSCAN 0x00008000 /* Uses the skip-scan algorithm */ #define WHERE_UNQ_WANTED 0x00010000 /* WHERE_ONEROW would have been helpful*/