## Artifact 124d970450955a6982e174b07c320ae6d62a595c:

- File src/whereInt.h — part of check-in [e62aab5e] at 2014-09-06 16:39:46 on branch trunk — Fix typos in comments. No code changes. (user: peter.d.reid size: 21530) [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 chosen 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*/