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Diffstat (limited to 'src/whereInt.h')
| -rw-r--r-- | src/whereInt.h | 461 |
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diff --git a/src/whereInt.h b/src/whereInt.h new file mode 100644 index 0000000..81f4a03 --- /dev/null +++ b/src/whereInt.h @@ -0,0 +1,461 @@ +/* +** 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*/ |