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Diffstat (limited to 'ext/misc/amatch.c')
| -rw-r--r-- | ext/misc/amatch.c | 1483 |
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diff --git a/ext/misc/amatch.c b/ext/misc/amatch.c new file mode 100644 index 0000000..b613080 --- /dev/null +++ b/ext/misc/amatch.c @@ -0,0 +1,1483 @@ +/* +** 2013-03-14 +** +** 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 code for a demonstration virtual table that finds +** "approximate matches" - strings from a finite set that are nearly the +** same as a single input string. The virtual table is called "amatch". +** +** A amatch virtual table is created like this: +** +** CREATE VIRTUAL TABLE f USING approximate_match( +** vocabulary_table=<tablename>, -- V +** vocabulary_word=<columnname>, -- W +** vocabulary_language=<columnname>, -- L +** edit_distances=<edit-cost-table> +** ); +** +** When it is created, the new amatch table must be supplied with the +** the name of a table V and columns V.W and V.L such that +** +** SELECT W FROM V WHERE L=$language +** +** returns the allowed vocabulary for the match. If the "vocabulary_language" +** or L columnname is left unspecified or is an empty string, then no +** filtering of the vocabulary by language is performed. +** +** For efficiency, it is essential that the vocabulary table be indexed: +** +** CREATE vocab_index ON V(W) +** +** A separate edit-cost-table provides scoring information that defines +** what it means for one string to be "close" to another. +** +** The edit-cost-table must contain exactly four columns (more precisely, +** the statement "SELECT * FROM <edit-cost-table>" must return records +** that consist of four columns). It does not matter what the columns are +** named. +** +** Each row in the edit-cost-table represents a single character +** transformation going from user input to the vocabulary. The leftmost +** column of the row (column 0) contains an integer identifier of the +** language to which the transformation rule belongs (see "MULTIPLE LANGUAGES" +** below). The second column of the row (column 1) contains the input +** character or characters - the characters of user input. The third +** column contains characters as they appear in the vocabulary table. +** And the fourth column contains the integer cost of making the +** transformation. For example: +** +** CREATE TABLE f_data(iLang, cFrom, cTo, Cost); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, '', 'a', 100); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, 'b', '', 87); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, 'o', 'oe', 38); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, 'oe', 'o', 40); +** +** The first row inserted into the edit-cost-table by the SQL script +** above indicates that the cost of having an extra 'a' in the vocabulary +** table that is missing in the user input 100. (All costs are integers. +** Overall cost must not exceed 16777216.) The second INSERT statement +** creates a rule saying that the cost of having a single letter 'b' in +** user input which is missing in the vocabulary table is 87. The third +** INSERT statement mean that the cost of matching an 'o' in user input +** against an 'oe' in the vocabulary table is 38. And so forth. +** +** The following rules are special: +** +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, '?', '', 97); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, '', '?', 98); +** INSERT INTO f_data(iLang, cFrom, cTo, Cost) VALUES(0, '?', '?', 99); +** +** The '?' to '' rule is the cost of having any single character in the input +** that is not found in the vocabular. The '' to '?' rule is the cost of +** having a character in the vocabulary table that is missing from input. +** And the '?' to '?' rule is the cost of doing an arbitrary character +** substitution. These three generic rules apply across all languages. +** In other words, the iLang field is ignored for the generic substitution +** rules. If more than one cost is given for a generic substitution rule, +** then the lowest cost is used. +** +** Once it has been created, the amatch virtual table can be queried +** as follows: +** +** SELECT word, distance FROM f +** WHERE word MATCH 'abcdefg' +** AND distance<200; +** +** This query outputs the strings contained in the T(F) field that +** are close to "abcdefg" and in order of increasing distance. No string +** is output more than once. If there are multiple ways to transform the +** target string ("abcdefg") into a string in the vocabulary table then +** the lowest cost transform is the one that is returned. In this example, +** the search is limited to strings with a total distance of less than 200. +** +** For efficiency, it is important to put tight bounds on the distance. +** The time and memory space needed to perform this query is exponential +** in the maximum distance. A good rule of thumb is to limit the distance +** to no more than 1.5 or 2 times the maximum cost of any rule in the +** edit-cost-table. +** +** The amatch is a read-only table. Any attempt to DELETE, INSERT, or +** UPDATE on a amatch table will throw an error. +** +** It is important to put some kind of a limit on the amatch output. This +** can be either in the form of a LIMIT clause at the end of the query, +** or better, a "distance<NNN" constraint where NNN is some number. The +** running time and memory requirement is exponential in the value of NNN +** so you want to make sure that NNN is not too big. A value of NNN that +** is about twice the average transformation cost seems to give good results. +** +** The amatch table can be useful for tasks such as spelling correction. +** Suppose all allowed words are in table vocabulary(w). Then one would create +** an amatch virtual table like this: +** +** CREATE VIRTUAL TABLE ex1 USING amatch( +** vocabtable=vocabulary, +** vocabcolumn=w, +** edit_distances=ec1 +** ); +** +** Then given an input word $word, look up close spellings this way: +** +** SELECT word, distance FROM ex1 +** WHERE word MATCH $word AND distance<200; +** +** MULTIPLE LANGUAGES +** +** Normally, the "iLang" value associated with all character transformations +** in the edit-cost-table is zero. However, if required, the amatch +** virtual table allows multiple languages to be defined. Each query uses +** only a single iLang value. This allows, for example, a single +** amatch table to support multiple languages. +** +** By default, only the rules with iLang=0 are used. To specify an +** alternative language, a "language = ?" expression must be added to the +** WHERE clause of a SELECT, where ? is the integer identifier of the desired +** language. For example: +** +** SELECT word, distance FROM ex1 +** WHERE word MATCH $word +** AND distance<=200 +** AND language=1 -- Specify use language 1 instead of 0 +** +** If no "language = ?" constraint is specified in the WHERE clause, language +** 0 is used. +** +** LIMITS +** +** The maximum language number is 2147483647. The maximum length of either +** of the strings in the second or third column of the amatch data table +** is 50 bytes. The maximum cost on a rule is 1000. +*/ +#include "sqlite3ext.h" +SQLITE_EXTENSION_INIT1 +#include <stdlib.h> +#include <string.h> +#include <assert.h> +#include <stdio.h> +#include <ctype.h> + +#ifndef SQLITE_OMIT_VIRTUALTABLE + +/* +** Forward declaration of objects used by this implementation +*/ +typedef struct amatch_vtab amatch_vtab; +typedef struct amatch_cursor amatch_cursor; +typedef struct amatch_rule amatch_rule; +typedef struct amatch_word amatch_word; +typedef struct amatch_avl amatch_avl; + + +/***************************************************************************** +** AVL Tree implementation +*/ +/* +** Objects that want to be members of the AVL tree should embedded an +** instance of this structure. +*/ +struct amatch_avl { + amatch_word *pWord; /* Points to the object being stored in the tree */ + char *zKey; /* Key. zero-terminated string. Must be unique */ + amatch_avl *pBefore; /* Other elements less than zKey */ + amatch_avl *pAfter; /* Other elements greater than zKey */ + amatch_avl *pUp; /* Parent element */ + short int height; /* Height of this node. Leaf==1 */ + short int imbalance; /* Height difference between pBefore and pAfter */ +}; + +/* Recompute the amatch_avl.height and amatch_avl.imbalance fields for p. +** Assume that the children of p have correct heights. +*/ +static void amatchAvlRecomputeHeight(amatch_avl *p){ + short int hBefore = p->pBefore ? p->pBefore->height : 0; + short int hAfter = p->pAfter ? p->pAfter->height : 0; + p->imbalance = hBefore - hAfter; /* -: pAfter higher. +: pBefore higher */ + p->height = (hBefore>hAfter ? hBefore : hAfter)+1; +} + +/* +** P B +** / \ / \ +** B Z ==> X P +** / \ / \ +** X Y Y Z +** +*/ +static amatch_avl *amatchAvlRotateBefore(amatch_avl *pP){ + amatch_avl *pB = pP->pBefore; + amatch_avl *pY = pB->pAfter; + pB->pUp = pP->pUp; + pB->pAfter = pP; + pP->pUp = pB; + pP->pBefore = pY; + if( pY ) pY->pUp = pP; + amatchAvlRecomputeHeight(pP); + amatchAvlRecomputeHeight(pB); + return pB; +} + +/* +** P A +** / \ / \ +** X A ==> P Z +** / \ / \ +** Y Z X Y +** +*/ +static amatch_avl *amatchAvlRotateAfter(amatch_avl *pP){ + amatch_avl *pA = pP->pAfter; + amatch_avl *pY = pA->pBefore; + pA->pUp = pP->pUp; + pA->pBefore = pP; + pP->pUp = pA; + pP->pAfter = pY; + if( pY ) pY->pUp = pP; + amatchAvlRecomputeHeight(pP); + amatchAvlRecomputeHeight(pA); + return pA; +} + +/* +** Return a pointer to the pBefore or pAfter pointer in the parent +** of p that points to p. Or if p is the root node, return pp. +*/ +static amatch_avl **amatchAvlFromPtr(amatch_avl *p, amatch_avl **pp){ + amatch_avl *pUp = p->pUp; + if( pUp==0 ) return pp; + if( pUp->pAfter==p ) return &pUp->pAfter; + return &pUp->pBefore; +} + +/* +** Rebalance all nodes starting with p and working up to the root. +** Return the new root. +*/ +static amatch_avl *amatchAvlBalance(amatch_avl *p){ + amatch_avl *pTop = p; + amatch_avl **pp; + while( p ){ + amatchAvlRecomputeHeight(p); + if( p->imbalance>=2 ){ + amatch_avl *pB = p->pBefore; + if( pB->imbalance<0 ) p->pBefore = amatchAvlRotateAfter(pB); + pp = amatchAvlFromPtr(p,&p); + p = *pp = amatchAvlRotateBefore(p); + }else if( p->imbalance<=(-2) ){ + amatch_avl *pA = p->pAfter; + if( pA->imbalance>0 ) p->pAfter = amatchAvlRotateBefore(pA); + pp = amatchAvlFromPtr(p,&p); + p = *pp = amatchAvlRotateAfter(p); + } + pTop = p; + p = p->pUp; + } + return pTop; +} + +/* Search the tree rooted at p for an entry with zKey. Return a pointer +** to the entry or return NULL. +*/ +static amatch_avl *amatchAvlSearch(amatch_avl *p, const char *zKey){ + int c; + while( p && (c = strcmp(zKey, p->zKey))!=0 ){ + p = (c<0) ? p->pBefore : p->pAfter; + } + return p; +} + +/* Find the first node (the one with the smallest key). +*/ +static amatch_avl *amatchAvlFirst(amatch_avl *p){ + if( p ) while( p->pBefore ) p = p->pBefore; + return p; +} + +#if 0 /* NOT USED */ +/* Return the node with the next larger key after p. +*/ +static amatch_avl *amatchAvlNext(amatch_avl *p){ + amatch_avl *pPrev = 0; + while( p && p->pAfter==pPrev ){ + pPrev = p; + p = p->pUp; + } + if( p && pPrev==0 ){ + p = amatchAvlFirst(p->pAfter); + } + return p; +} +#endif + +#if 0 /* NOT USED */ +/* Verify AVL tree integrity +*/ +static int amatchAvlIntegrity(amatch_avl *pHead){ + amatch_avl *p; + if( pHead==0 ) return 1; + if( (p = pHead->pBefore)!=0 ){ + assert( p->pUp==pHead ); + assert( amatchAvlIntegrity(p) ); + assert( strcmp(p->zKey, pHead->zKey)<0 ); + while( p->pAfter ) p = p->pAfter; + assert( strcmp(p->zKey, pHead->zKey)<0 ); + } + if( (p = pHead->pAfter)!=0 ){ + assert( p->pUp==pHead ); + assert( amatchAvlIntegrity(p) ); + assert( strcmp(p->zKey, pHead->zKey)>0 ); + p = amatchAvlFirst(p); + assert( strcmp(p->zKey, pHead->zKey)>0 ); + } + return 1; +} +static int amatchAvlIntegrity2(amatch_avl *pHead){ + amatch_avl *p, *pNext; + for(p=amatchAvlFirst(pHead); p; p=pNext){ + pNext = amatchAvlNext(p); + if( pNext==0 ) break; + assert( strcmp(p->zKey, pNext->zKey)<0 ); + } + return 1; +} +#endif + +/* Insert a new node pNew. Return NULL on success. If the key is not +** unique, then do not perform the insert but instead leave pNew unchanged +** and return a pointer to an existing node with the same key. +*/ +static amatch_avl *amatchAvlInsert(amatch_avl **ppHead, amatch_avl *pNew){ + int c; + amatch_avl *p = *ppHead; + if( p==0 ){ + p = pNew; + pNew->pUp = 0; + }else{ + while( p ){ + c = strcmp(pNew->zKey, p->zKey); + if( c<0 ){ + if( p->pBefore ){ + p = p->pBefore; + }else{ + p->pBefore = pNew; + pNew->pUp = p; + break; + } + }else if( c>0 ){ + if( p->pAfter ){ + p = p->pAfter; + }else{ + p->pAfter = pNew; + pNew->pUp = p; + break; + } + }else{ + return p; + } + } + } + pNew->pBefore = 0; + pNew->pAfter = 0; + pNew->height = 1; + pNew->imbalance = 0; + *ppHead = amatchAvlBalance(p); + /* assert( amatchAvlIntegrity(*ppHead) ); */ + /* assert( amatchAvlIntegrity2(*ppHead) ); */ + return 0; +} + +/* Remove node pOld from the tree. pOld must be an element of the tree or +** the AVL tree will become corrupt. +*/ +static void amatchAvlRemove(amatch_avl **ppHead, amatch_avl *pOld){ + amatch_avl **ppParent; + amatch_avl *pBalance; + /* assert( amatchAvlSearch(*ppHead, pOld->zKey)==pOld ); */ + ppParent = amatchAvlFromPtr(pOld, ppHead); + if( pOld->pBefore==0 && pOld->pAfter==0 ){ + *ppParent = 0; + pBalance = pOld->pUp; + }else if( pOld->pBefore && pOld->pAfter ){ + amatch_avl *pX, *pY; + pX = amatchAvlFirst(pOld->pAfter); + *amatchAvlFromPtr(pX, 0) = pX->pAfter; + if( pX->pAfter ) pX->pAfter->pUp = pX->pUp; + pBalance = pX->pUp; + pX->pAfter = pOld->pAfter; + if( pX->pAfter ){ + pX->pAfter->pUp = pX; + }else{ + assert( pBalance==pOld ); + pBalance = pX; + } + pX->pBefore = pY = pOld->pBefore; + if( pY ) pY->pUp = pX; + pX->pUp = pOld->pUp; + *ppParent = pX; + }else if( pOld->pBefore==0 ){ + *ppParent = pBalance = pOld->pAfter; + pBalance->pUp = pOld->pUp; + }else if( pOld->pAfter==0 ){ + *ppParent = pBalance = pOld->pBefore; + pBalance->pUp = pOld->pUp; + } + *ppHead = amatchAvlBalance(pBalance); + pOld->pUp = 0; + pOld->pBefore = 0; + pOld->pAfter = 0; + /* assert( amatchAvlIntegrity(*ppHead) ); */ + /* assert( amatchAvlIntegrity2(*ppHead) ); */ +} +/* +** End of the AVL Tree implementation +******************************************************************************/ + + +/* +** Various types. +** +** amatch_cost is the "cost" of an edit operation. +** +** amatch_len is the length of a matching string. +** +** amatch_langid is an ruleset identifier. +*/ +typedef int amatch_cost; +typedef signed char amatch_len; +typedef int amatch_langid; + +/* +** Limits +*/ +#define AMATCH_MX_LENGTH 50 /* Maximum length of a rule string */ +#define AMATCH_MX_LANGID 2147483647 /* Maximum rule ID */ +#define AMATCH_MX_COST 1000 /* Maximum single-rule cost */ + +/* +** A match or partial match +*/ +struct amatch_word { + amatch_word *pNext; /* Next on a list of all amatch_words */ + amatch_avl sCost; /* Linkage of this node into the cost tree */ + amatch_avl sWord; /* Linkage of this node into the word tree */ + amatch_cost rCost; /* Cost of the match so far */ + int iSeq; /* Sequence number */ + char zCost[10]; /* Cost key (text rendering of rCost) */ + short int nMatch; /* Input characters matched */ + char zWord[4]; /* Text of the word. Extra space appended as needed */ +}; + +/* +** Each transformation rule is stored as an instance of this object. +** All rules are kept on a linked list sorted by rCost. +*/ +struct amatch_rule { + amatch_rule *pNext; /* Next rule in order of increasing rCost */ + char *zFrom; /* Transform from (a string from user input) */ + amatch_cost rCost; /* Cost of this transformation */ + amatch_langid iLang; /* The langauge to which this rule belongs */ + amatch_len nFrom, nTo; /* Length of the zFrom and zTo strings */ + char zTo[4]; /* Tranform to V.W value (extra space appended) */ +}; + +/* +** A amatch virtual-table object +*/ +struct amatch_vtab { + sqlite3_vtab base; /* Base class - must be first */ + char *zClassName; /* Name of this class. Default: "amatch" */ + char *zDb; /* Name of database. (ex: "main") */ + char *zSelf; /* Name of this virtual table */ + char *zCostTab; /* Name of edit-cost-table */ + char *zVocabTab; /* Name of vocabulary table */ + char *zVocabWord; /* Name of vocabulary table word column */ + char *zVocabLang; /* Name of vocabulary table language column */ + amatch_rule *pRule; /* All active rules in this amatch */ + amatch_cost rIns; /* Generic insertion cost '' -> ? */ + amatch_cost rDel; /* Generic deletion cost ? -> '' */ + amatch_cost rSub; /* Generic substitution cost ? -> ? */ + sqlite3 *db; /* The database connection */ + sqlite3_stmt *pVCheck; /* Query to check zVocabTab */ + int nCursor; /* Number of active cursors */ +}; + +/* A amatch cursor object */ +struct amatch_cursor { + sqlite3_vtab_cursor base; /* Base class - must be first */ + sqlite3_int64 iRowid; /* The rowid of the current word */ + amatch_langid iLang; /* Use this language ID */ + amatch_cost rLimit; /* Maximum cost of any term */ + int nBuf; /* Space allocated for zBuf */ + int oomErr; /* True following an OOM error */ + int nWord; /* Number of amatch_word objects */ + char *zBuf; /* Temp-use buffer space */ + char *zInput; /* Input word to match against */ + amatch_vtab *pVtab; /* The virtual table this cursor belongs to */ + amatch_word *pAllWords; /* List of all amatch_word objects */ + amatch_word *pCurrent; /* Most recent solution */ + amatch_avl *pCost; /* amatch_word objects keyed by iCost */ + amatch_avl *pWord; /* amatch_word objects keyed by zWord */ +}; + +/* +** The two input rule lists are both sorted in order of increasing +** cost. Merge them together into a single list, sorted by cost, and +** return a pointer to the head of that list. +*/ +static amatch_rule *amatchMergeRules(amatch_rule *pA, amatch_rule *pB){ + amatch_rule head; + amatch_rule *pTail; + + pTail = &head; + while( pA && pB ){ + if( pA->rCost<=pB->rCost ){ + pTail->pNext = pA; + pTail = pA; + pA = pA->pNext; + }else{ + pTail->pNext = pB; + pTail = pB; + pB = pB->pNext; + } + } + if( pA==0 ){ + pTail->pNext = pB; + }else{ + pTail->pNext = pA; + } + return head.pNext; +} + +/* +** Statement pStmt currently points to a row in the amatch data table. This +** function allocates and populates a amatch_rule structure according to +** the content of the row. +** +** If successful, *ppRule is set to point to the new object and SQLITE_OK +** is returned. Otherwise, *ppRule is zeroed, *pzErr may be set to point +** to an error message and an SQLite error code returned. +*/ +static int amatchLoadOneRule( + amatch_vtab *p, /* Fuzzer virtual table handle */ + sqlite3_stmt *pStmt, /* Base rule on statements current row */ + amatch_rule **ppRule, /* OUT: New rule object */ + char **pzErr /* OUT: Error message */ +){ + sqlite3_int64 iLang = sqlite3_column_int64(pStmt, 0); + const char *zFrom = (const char *)sqlite3_column_text(pStmt, 1); + const char *zTo = (const char *)sqlite3_column_text(pStmt, 2); + amatch_cost rCost = sqlite3_column_int(pStmt, 3); + + int rc = SQLITE_OK; /* Return code */ + int nFrom; /* Size of string zFrom, in bytes */ + int nTo; /* Size of string zTo, in bytes */ + amatch_rule *pRule = 0; /* New rule object to return */ + + if( zFrom==0 ) zFrom = ""; + if( zTo==0 ) zTo = ""; + nFrom = (int)strlen(zFrom); + nTo = (int)strlen(zTo); + + /* Silently ignore null transformations */ + if( strcmp(zFrom, zTo)==0 ){ + if( zFrom[0]=='?' && zFrom[1]==0 ){ + if( p->rSub==0 || p->rSub>rCost ) p->rSub = rCost; + } + *ppRule = 0; + return SQLITE_OK; + } + + if( rCost<=0 || rCost>AMATCH_MX_COST ){ + *pzErr = sqlite3_mprintf("%s: cost must be between 1 and %d", + p->zClassName, AMATCH_MX_COST + ); + rc = SQLITE_ERROR; + }else + if( nFrom>AMATCH_MX_LENGTH || nTo>AMATCH_MX_LENGTH ){ + *pzErr = sqlite3_mprintf("%s: maximum string length is %d", + p->zClassName, AMATCH_MX_LENGTH + ); + rc = SQLITE_ERROR; + }else + if( iLang<0 || iLang>AMATCH_MX_LANGID ){ + *pzErr = sqlite3_mprintf("%s: iLang must be between 0 and %d", + p->zClassName, AMATCH_MX_LANGID + ); + rc = SQLITE_ERROR; + }else + if( strcmp(zFrom,"")==0 && strcmp(zTo,"?")==0 ){ + if( p->rIns==0 || p->rIns>rCost ) p->rIns = rCost; + }else + if( strcmp(zFrom,"?")==0 && strcmp(zTo,"")==0 ){ + if( p->rDel==0 || p->rDel>rCost ) p->rDel = rCost; + }else + { + pRule = sqlite3_malloc( sizeof(*pRule) + nFrom + nTo ); + if( pRule==0 ){ + rc = SQLITE_NOMEM; + }else{ + memset(pRule, 0, sizeof(*pRule)); + pRule->zFrom = &pRule->zTo[nTo+1]; + pRule->nFrom = nFrom; + memcpy(pRule->zFrom, zFrom, nFrom+1); + memcpy(pRule->zTo, zTo, nTo+1); + pRule->nTo = nTo; + pRule->rCost = rCost; + pRule->iLang = (int)iLang; + } + } + + *ppRule = pRule; + return rc; +} + +/* +** Free all the content in the edit-cost-table +*/ +static void amatchFreeRules(amatch_vtab *p){ + while( p->pRule ){ + amatch_rule *pRule = p->pRule; + p->pRule = pRule->pNext; + sqlite3_free(pRule); + } + p->pRule = 0; +} + +/* +** Load the content of the amatch data table into memory. +*/ +static int amatchLoadRules( + sqlite3 *db, /* Database handle */ + amatch_vtab *p, /* Virtual amatch table to configure */ + char **pzErr /* OUT: Error message */ +){ + int rc = SQLITE_OK; /* Return code */ + char *zSql; /* SELECT used to read from rules table */ + amatch_rule *pHead = 0; + + zSql = sqlite3_mprintf("SELECT * FROM %Q.%Q", p->zDb, p->zCostTab); + if( zSql==0 ){ + rc = SQLITE_NOMEM; + }else{ + int rc2; /* finalize() return code */ + sqlite3_stmt *pStmt = 0; + rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0); + if( rc!=SQLITE_OK ){ + *pzErr = sqlite3_mprintf("%s: %s", p->zClassName, sqlite3_errmsg(db)); + }else if( sqlite3_column_count(pStmt)!=4 ){ + *pzErr = sqlite3_mprintf("%s: %s has %d columns, expected 4", + p->zClassName, p->zCostTab, sqlite3_column_count(pStmt) + ); + rc = SQLITE_ERROR; + }else{ + while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){ + amatch_rule *pRule = 0; + rc = amatchLoadOneRule(p, pStmt, &pRule, pzErr); + if( pRule ){ + pRule->pNext = pHead; + pHead = pRule; + } + } + } + rc2 = sqlite3_finalize(pStmt); + if( rc==SQLITE_OK ) rc = rc2; + } + sqlite3_free(zSql); + + /* All rules are now in a singly linked list starting at pHead. This + ** block sorts them by cost and then sets amatch_vtab.pRule to point to + ** point to the head of the sorted list. + */ + if( rc==SQLITE_OK ){ + unsigned int i; + amatch_rule *pX; + amatch_rule *a[15]; + for(i=0; i<sizeof(a)/sizeof(a[0]); i++) a[i] = 0; + while( (pX = pHead)!=0 ){ + pHead = pX->pNext; + pX->pNext = 0; + for(i=0; a[i] && i<sizeof(a)/sizeof(a[0])-1; i++){ + pX = amatchMergeRules(a[i], pX); + a[i] = 0; + } + a[i] = amatchMergeRules(a[i], pX); + } + for(pX=a[0], i=1; i<sizeof(a)/sizeof(a[0]); i++){ + pX = amatchMergeRules(a[i], pX); + } + p->pRule = amatchMergeRules(p->pRule, pX); + }else{ + /* An error has occurred. Setting p->pRule to point to the head of the + ** allocated list ensures that the list will be cleaned up in this case. + */ + assert( p->pRule==0 ); + p->pRule = pHead; + } + + return rc; +} + +/* +** This function converts an SQL quoted string into an unquoted string +** and returns a pointer to a buffer allocated using sqlite3_malloc() +** containing the result. The caller should eventually free this buffer +** using sqlite3_free. +** +** Examples: +** +** "abc" becomes abc +** 'xyz' becomes xyz +** [pqr] becomes pqr +** `mno` becomes mno +*/ +static char *amatchDequote(const char *zIn){ + int nIn; /* Size of input string, in bytes */ + char *zOut; /* Output (dequoted) string */ + + nIn = (int)strlen(zIn); + zOut = sqlite3_malloc(nIn+1); + if( zOut ){ + char q = zIn[0]; /* Quote character (if any ) */ + + if( q!='[' && q!= '\'' && q!='"' && q!='`' ){ + memcpy(zOut, zIn, nIn+1); + }else{ + int iOut = 0; /* Index of next byte to write to output */ + int iIn; /* Index of next byte to read from input */ + + if( q=='[' ) q = ']'; + for(iIn=1; iIn<nIn; iIn++){ + if( zIn[iIn]==q ) iIn++; + zOut[iOut++] = zIn[iIn]; + } + } + assert( (int)strlen(zOut)<=nIn ); + } + return zOut; +} + +/* +** Deallocate the pVCheck prepared statement. +*/ +static void amatchVCheckClear(amatch_vtab *p){ + if( p->pVCheck ){ + sqlite3_finalize(p->pVCheck); + p->pVCheck = 0; + } +} + +/* +** Deallocate an amatch_vtab object +*/ +static void amatchFree(amatch_vtab *p){ + if( p ){ + amatchFreeRules(p); + amatchVCheckClear(p); + sqlite3_free(p->zClassName); + sqlite3_free(p->zDb); + sqlite3_free(p->zCostTab); + sqlite3_free(p->zVocabTab); + sqlite3_free(p->zVocabWord); + sqlite3_free(p->zVocabLang); + memset(p, 0, sizeof(*p)); + sqlite3_free(p); + } +} + +/* +** xDisconnect/xDestroy method for the amatch module. +*/ +static int amatchDisconnect(sqlite3_vtab *pVtab){ + amatch_vtab *p = (amatch_vtab*)pVtab; + assert( p->nCursor==0 ); + amatchFree(p); + return SQLITE_OK; +} + +/* +** Check to see if the argument is of the form: +** +** KEY = VALUE +** +** If it is, return a pointer to the first character of VALUE. +** If not, return NULL. Spaces around the = are ignored. +*/ +static const char *amatchValueOfKey(const char *zKey, const char *zStr){ + int nKey = (int)strlen(zKey); + int nStr = (int)strlen(zStr); + int i; + if( nStr<nKey+1 ) return 0; + if( memcmp(zStr, zKey, nKey)!=0 ) return 0; + for(i=nKey; isspace(zStr[i]); i++){} + if( zStr[i]!='=' ) return 0; + i++; + while( isspace(zStr[i]) ){ i++; } + return zStr+i; +} + +/* +** xConnect/xCreate method for the amatch module. Arguments are: +** +** argv[0] -> module name ("approximate_match") +** argv[1] -> database name +** argv[2] -> table name +** argv[3...] -> arguments +*/ +static int amatchConnect( + sqlite3 *db, + void *pAux, + int argc, const char *const*argv, + sqlite3_vtab **ppVtab, + char **pzErr +){ + int rc = SQLITE_OK; /* Return code */ + amatch_vtab *pNew = 0; /* New virtual table */ + const char *zModule = argv[0]; + const char *zDb = argv[1]; + const char *zVal; + int i; + + (void)pAux; + *ppVtab = 0; + pNew = sqlite3_malloc( sizeof(*pNew) ); + if( pNew==0 ) return SQLITE_NOMEM; + rc = SQLITE_NOMEM; + memset(pNew, 0, sizeof(*pNew)); + pNew->db = db; + pNew->zClassName = sqlite3_mprintf("%s", zModule); + if( pNew->zClassName==0 ) goto amatchConnectError; + pNew->zDb = sqlite3_mprintf("%s", zDb); + if( pNew->zDb==0 ) goto amatchConnectError; + pNew->zSelf = sqlite3_mprintf("%s", argv[2]); + if( pNew->zSelf==0 ) goto amatchConnectError; + for(i=3; i<argc; i++){ + zVal = amatchValueOfKey("vocabulary_table", argv[i]); + if( zVal ){ + sqlite3_free(pNew->zVocabTab); + pNew->zVocabTab = amatchDequote(zVal); + if( pNew->zVocabTab==0 ) goto amatchConnectError; + continue; + } + zVal = amatchValueOfKey("vocabulary_word", argv[i]); + if( zVal ){ + sqlite3_free(pNew->zVocabWord); + pNew->zVocabWord = amatchDequote(zVal); + if( pNew->zVocabWord==0 ) goto amatchConnectError; + continue; + } + zVal = amatchValueOfKey("vocabulary_language", argv[i]); + if( zVal ){ + sqlite3_free(pNew->zVocabLang); + pNew->zVocabLang = amatchDequote(zVal); + if( pNew->zVocabLang==0 ) goto amatchConnectError; + continue; + } + zVal = amatchValueOfKey("edit_distances", argv[i]); + if( zVal ){ + sqlite3_free(pNew->zCostTab); + pNew->zCostTab = amatchDequote(zVal); + if( pNew->zCostTab==0 ) goto amatchConnectError; + continue; + } + *pzErr = sqlite3_mprintf("unrecognized argument: [%s]\n", argv[i]); + amatchFree(pNew); + *ppVtab = 0; + return SQLITE_ERROR; + } + rc = SQLITE_OK; + if( pNew->zCostTab==0 ){ + *pzErr = sqlite3_mprintf("no edit_distances table specified"); + rc = SQLITE_ERROR; + }else{ + rc = amatchLoadRules(db, pNew, pzErr); + } + if( rc==SQLITE_OK ){ + rc = sqlite3_declare_vtab(db, + "CREATE TABLE x(word,distance,language," + "command HIDDEN,nword HIDDEN)" + ); +#define AMATCH_COL_WORD 0 +#define AMATCH_COL_DISTANCE 1 +#define AMATCH_COL_LANGUAGE 2 +#define AMATCH_COL_COMMAND 3 +#define AMATCH_COL_NWORD 4 + } + if( rc!=SQLITE_OK ){ + amatchFree(pNew); + } + *ppVtab = &pNew->base; + return rc; + +amatchConnectError: + amatchFree(pNew); + return rc; +} + +/* +** Open a new amatch cursor. +*/ +static int amatchOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){ + amatch_vtab *p = (amatch_vtab*)pVTab; + amatch_cursor *pCur; + pCur = sqlite3_malloc( sizeof(*pCur) ); + if( pCur==0 ) return SQLITE_NOMEM; + memset(pCur, 0, sizeof(*pCur)); + pCur->pVtab = p; + *ppCursor = &pCur->base; + p->nCursor++; + return SQLITE_OK; +} + +/* +** Free up all the memory allocated by a cursor. Set it rLimit to 0 +** to indicate that it is at EOF. +*/ +static void amatchClearCursor(amatch_cursor *pCur){ + amatch_word *pWord, *pNextWord; + for(pWord=pCur->pAllWords; pWord; pWord=pNextWord){ + pNextWord = pWord->pNext; + sqlite3_free(pWord); + } + pCur->pAllWords = 0; + sqlite3_free(pCur->zInput); + pCur->zInput = 0; + pCur->pCost = 0; + pCur->pWord = 0; + pCur->pCurrent = 0; + pCur->rLimit = 1000000; + pCur->iLang = 0; + pCur->nWord = 0; +} + +/* +** Close a amatch cursor. +*/ +static int amatchClose(sqlite3_vtab_cursor *cur){ + amatch_cursor *pCur = (amatch_cursor *)cur; + amatchClearCursor(pCur); + pCur->pVtab->nCursor--; + sqlite3_free(pCur); + return SQLITE_OK; +} + +/* +** Render a 24-bit unsigned integer as a 4-byte base-64 number. +*/ +static void amatchEncodeInt(int x, char *z){ + static const char a[] = + "0123456789" + "ABCDEFGHIJ" + "KLMNOPQRST" + "UVWXYZ^abc" + "defghijklm" + "nopqrstuvw" + "xyz~"; + z[0] = a[(x>>18)&0x3f]; + z[1] = a[(x>>12)&0x3f]; + z[2] = a[(x>>6)&0x3f]; + z[3] = a[x&0x3f]; +} + +/* +** Write the zCost[] field for a amatch_word object +*/ +static void amatchWriteCost(amatch_word *pWord){ + amatchEncodeInt(pWord->rCost, pWord->zCost); + amatchEncodeInt(pWord->iSeq, pWord->zCost+4); + pWord->zCost[8] = 0; +} + +/* +** Add a new amatch_word object to the queue. +** +** If a prior amatch_word object with the same zWord, and nMatch +** already exists, update its rCost (if the new rCost is less) but +** otherwise leave it unchanged. Do not add a duplicate. +** +** Do nothing if the cost exceeds threshold. +*/ +static void amatchAddWord( + amatch_cursor *pCur, + amatch_cost rCost, + int nMatch, + const char *zWordBase, + const char *zWordTail +){ + amatch_word *pWord; + amatch_avl *pNode; + amatch_avl *pOther; + int nBase, nTail; + char zBuf[4]; + + if( rCost>pCur->rLimit ){ + return; + } + nBase = (int)strlen(zWordBase); + nTail = (int)strlen(zWordTail); + if( nBase+nTail+3>pCur->nBuf ){ + pCur->nBuf = nBase+nTail+100; + pCur->zBuf = sqlite3_realloc(pCur->zBuf, pCur->nBuf); + if( pCur->zBuf==0 ){ + pCur->nBuf = 0; + return; + } + } + amatchEncodeInt(nMatch, zBuf); + memcpy(pCur->zBuf, zBuf+2, 2); + memcpy(pCur->zBuf+2, zWordBase, nBase); + memcpy(pCur->zBuf+2+nBase, zWordTail, nTail+1); + pNode = amatchAvlSearch(pCur->pWord, pCur->zBuf); + if( pNode ){ + pWord = pNode->pWord; + if( pWord->rCost>rCost ){ +#ifdef AMATCH_TRACE_1 + printf("UPDATE [%s][%.*s^%s] %d (\"%s\" \"%s\")\n", + pWord->zWord+2, pWord->nMatch, pCur->zInput, pCur->zInput, + pWord->rCost, pWord->zWord, pWord->zCost); +#endif + amatchAvlRemove(&pCur->pCost, &pWord->sCost); + pWord->rCost = rCost; + amatchWriteCost(pWord); +#ifdef AMATCH_TRACE_1 + printf(" ---> %d (\"%s\" \"%s\")\n", + pWord->rCost, pWord->zWord, pWord->zCost); +#endif + pOther = amatchAvlInsert(&pCur->pCost, &pWord->sCost); + assert( pOther==0 ); (void)pOther; + } + return; + } + pWord = sqlite3_malloc( sizeof(*pWord) + nBase + nTail - 1 ); + if( pWord==0 ) return; + memset(pWord, 0, sizeof(*pWord)); + pWord->rCost = rCost; + pWord->iSeq = pCur->nWord++; + amatchWriteCost(pWord); + pWord->nMatch = nMatch; + pWord->pNext = pCur->pAllWords; + pCur->pAllWords = pWord; + pWord->sCost.zKey = pWord->zCost; + pWord->sCost.pWord = pWord; + pOther = amatchAvlInsert(&pCur->pCost, &pWord->sCost); + assert( pOther==0 ); (void)pOther; + pWord->sWord.zKey = pWord->zWord; + pWord->sWord.pWord = pWord; + strcpy(pWord->zWord, pCur->zBuf); + pOther = amatchAvlInsert(&pCur->pWord, &pWord->sWord); + assert( pOther==0 ); (void)pOther; +#ifdef AMATCH_TRACE_1 + printf("INSERT [%s][%.*s^%s] %d (\"%s\" \"%s\")\n", pWord->zWord+2, + pWord->nMatch, pCur->zInput, pCur->zInput+pWord->nMatch, rCost, + pWord->zWord, pWord->zCost); +#endif +} + +/* +** Advance a cursor to its next row of output +*/ +static int amatchNext(sqlite3_vtab_cursor *cur){ + amatch_cursor *pCur = (amatch_cursor*)cur; + amatch_word *pWord = 0; + amatch_avl *pNode; + int isMatch = 0; + amatch_vtab *p = pCur->pVtab; + int nWord; + int rc; + int i; + const char *zW; + amatch_rule *pRule; + char *zBuf = 0; + char nBuf = 0; + char zNext[8]; + char zNextIn[8]; + int nNextIn; + + if( p->pVCheck==0 ){ + char *zSql; + if( p->zVocabLang && p->zVocabLang[0] ){ + zSql = sqlite3_mprintf( + "SELECT \"%s\" FROM \"%s\"", + " WHERE \"%w\">=?1 AND \"%w\"=?2" + " ORDER BY 1", + p->zVocabWord, p->zVocabTab, + p->zVocabWord, p->zVocabLang + ); + }else{ + zSql = sqlite3_mprintf( + "SELECT \"%s\" FROM \"%s\"" + " WHERE \"%w\">=?1" + " ORDER BY 1", + p->zVocabWord, p->zVocabTab, + p->zVocabWord + ); + } + rc = sqlite3_prepare_v2(p->db, zSql, -1, &p->pVCheck, 0); + sqlite3_free(zSql); + if( rc ) return rc; + } + sqlite3_bind_int(p->pVCheck, 2, pCur->iLang); + + do{ + pNode = amatchAvlFirst(pCur->pCost); + if( pNode==0 ){ + pWord = 0; + break; + } + pWord = pNode->pWord; + amatchAvlRemove(&pCur->pCost, &pWord->sCost); + +#ifdef AMATCH_TRACE_1 + printf("PROCESS [%s][%.*s^%s] %d (\"%s\" \"%s\")\n", + pWord->zWord+2, pWord->nMatch, pCur->zInput, pCur->zInput+pWord->nMatch, + pWord->rCost, pWord->zWord, pWord->zCost); +#endif + nWord = (int)strlen(pWord->zWord+2); + if( nWord+20>nBuf ){ + nBuf = nWord+100; + zBuf = sqlite3_realloc(zBuf, nBuf); + if( zBuf==0 ) return SQLITE_NOMEM; + } + strcpy(zBuf, pWord->zWord+2); + zNext[0] = 0; + zNextIn[0] = pCur->zInput[pWord->nMatch]; + if( zNextIn[0] ){ + for(i=1; i<=4 && (pCur->zInput[pWord->nMatch+i]&0xc0)==0x80; i++){ + zNextIn[i] = pCur->zInput[pWord->nMatch+i]; + } + zNextIn[i] = 0; + nNextIn = i; + }else{ + nNextIn = 0; + } + + if( zNextIn[0] && zNextIn[0]!='*' ){ + sqlite3_reset(p->pVCheck); + strcat(zBuf, zNextIn); + sqlite3_bind_text(p->pVCheck, 1, zBuf, nWord+nNextIn, SQLITE_STATIC); + rc = sqlite3_step(p->pVCheck); + if( rc==SQLITE_ROW ){ + zW = (const char*)sqlite3_column_text(p->pVCheck, 0); + if( strncmp(zBuf, zW, nWord+nNextIn)==0 ){ + amatchAddWord(pCur, pWord->rCost, pWord->nMatch+nNextIn, zBuf, ""); + } + } + zBuf[nWord] = 0; + } + + while( 1 ){ + strcpy(zBuf+nWord, zNext); + sqlite3_reset(p->pVCheck); + sqlite3_bind_text(p->pVCheck, 1, zBuf, -1, SQLITE_TRANSIENT); + rc = sqlite3_step(p->pVCheck); + if( rc!=SQLITE_ROW ) break; + zW = (const char*)sqlite3_column_text(p->pVCheck, 0); + strcpy(zBuf+nWord, zNext); + if( strncmp(zW, zBuf, nWord)!=0 ) break; + if( (zNextIn[0]=='*' && zNextIn[1]==0) + || (zNextIn[0]==0 && zW[nWord]==0) + ){ + isMatch = 1; + zNextIn[0] = 0; + nNextIn = 0; + break; + } + zNext[0] = zW[nWord]; + for(i=1; i<=4 && (zW[nWord+i]&0xc0)==0x80; i++){ + zNext[i] = zW[nWord+i]; + } + zNext[i] = 0; + zBuf[nWord] = 0; + if( p->rIns>0 ){ + amatchAddWord(pCur, pWord->rCost+p->rIns, pWord->nMatch, + zBuf, zNext); + } + if( p->rSub>0 ){ + amatchAddWord(pCur, pWord->rCost+p->rSub, pWord->nMatch+nNextIn, + zBuf, zNext); + } + if( p->rIns<0 && p->rSub<0 ) break; + zNext[i-1]++; /* FIX ME */ + } + sqlite3_reset(p->pVCheck); + + if( p->rDel>0 ){ + zBuf[nWord] = 0; + amatchAddWord(pCur, pWord->rCost+p->rDel, pWord->nMatch+nNextIn, + zBuf, ""); + } + + for(pRule=p->pRule; pRule; pRule=pRule->pNext){ + if( pRule->iLang!=pCur->iLang ) continue; + if( strncmp(pRule->zFrom, pCur->zInput+pWord->nMatch, pRule->nFrom)==0 ){ + amatchAddWord(pCur, pWord->rCost+pRule->rCost, + pWord->nMatch+pRule->nFrom, pWord->zWord+2, pRule->zTo); + } + } + }while( !isMatch ); + pCur->pCurrent = pWord; + sqlite3_free(zBuf); + return SQLITE_OK; +} + +/* +** Called to "rewind" a cursor back to the beginning so that +** it starts its output over again. Always called at least once +** prior to any amatchColumn, amatchRowid, or amatchEof call. +*/ +static int amatchFilter( + sqlite3_vtab_cursor *pVtabCursor, + int idxNum, const char *idxStr, + int argc, sqlite3_value **argv +){ + amatch_cursor *pCur = (amatch_cursor *)pVtabCursor; + const char *zWord = "*"; + int idx; + + amatchClearCursor(pCur); + idx = 0; + if( idxNum & 1 ){ + zWord = (const char*)sqlite3_value_text(argv[0]); + idx++; + } + if( idxNum & 2 ){ + pCur->rLimit = (amatch_cost)sqlite3_value_int(argv[idx]); + idx++; + } + if( idxNum & 4 ){ + pCur->iLang = (amatch_cost)sqlite3_value_int(argv[idx]); + idx++; + } + pCur->zInput = sqlite3_mprintf("%s", zWord); + if( pCur->zInput==0 ) return SQLITE_NOMEM; + amatchAddWord(pCur, 0, 0, "", ""); + amatchNext(pVtabCursor); + + return SQLITE_OK; +} + +/* +** Only the word and distance columns have values. All other columns +** return NULL +*/ +static int amatchColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){ + amatch_cursor *pCur = (amatch_cursor*)cur; + switch( i ){ + case AMATCH_COL_WORD: { + sqlite3_result_text(ctx, pCur->pCurrent->zWord+2, -1, SQLITE_STATIC); + break; + } + case AMATCH_COL_DISTANCE: { + sqlite3_result_int(ctx, pCur->pCurrent->rCost); + break; + } + case AMATCH_COL_LANGUAGE: { + sqlite3_result_int(ctx, pCur->iLang); + break; + } + case AMATCH_COL_NWORD: { + sqlite3_result_int(ctx, pCur->nWord); + break; + } + default: { + sqlite3_result_null(ctx); + break; + } + } + return SQLITE_OK; +} + +/* +** The rowid. +*/ +static int amatchRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){ + amatch_cursor *pCur = (amatch_cursor*)cur; + *pRowid = pCur->iRowid; + return SQLITE_OK; +} + +/* +** EOF indicator +*/ +static int amatchEof(sqlite3_vtab_cursor *cur){ + amatch_cursor *pCur = (amatch_cursor*)cur; + return pCur->pCurrent==0; +} + +/* +** Search for terms of these forms: +** +** (A) word MATCH $str +** (B1) distance < $value +** (B2) distance <= $value +** (C) language == $language +** +** The distance< and distance<= are both treated as distance<=. +** The query plan number is a bit vector: +** +** bit 1: Term of the form (A) found +** bit 2: Term like (B1) or (B2) found +** bit 3: Term like (C) found +** +** If bit-1 is set, $str is always in filter.argv[0]. If bit-2 is set +** then $value is in filter.argv[0] if bit-1 is clear and is in +** filter.argv[1] if bit-1 is set. If bit-3 is set, then $ruleid is +** in filter.argv[0] if bit-1 and bit-2 are both zero, is in +** filter.argv[1] if exactly one of bit-1 and bit-2 are set, and is in +** filter.argv[2] if both bit-1 and bit-2 are set. +*/ +static int amatchBestIndex( + sqlite3_vtab *tab, + sqlite3_index_info *pIdxInfo +){ + int iPlan = 0; + int iDistTerm = -1; + int iLangTerm = -1; + int i; + const struct sqlite3_index_constraint *pConstraint; + + (void)tab; + pConstraint = pIdxInfo->aConstraint; + for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){ + if( pConstraint->usable==0 ) continue; + if( (iPlan & 1)==0 + && pConstraint->iColumn==0 + && pConstraint->op==SQLITE_INDEX_CONSTRAINT_MATCH + ){ + iPlan |= 1; + pIdxInfo->aConstraintUsage[i].argvIndex = 1; + pIdxInfo->aConstraintUsage[i].omit = 1; + } + if( (iPlan & 2)==0 + && pConstraint->iColumn==1 + && (pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT + || pConstraint->op==SQLITE_INDEX_CONSTRAINT_LE) + ){ + iPlan |= 2; + iDistTerm = i; + } + if( (iPlan & 4)==0 + && pConstraint->iColumn==2 + && pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ + ){ + iPlan |= 4; + pIdxInfo->aConstraintUsage[i].omit = 1; + iLangTerm = i; + } + } + if( iPlan & 2 ){ + pIdxInfo->aConstraintUsage[iDistTerm].argvIndex = 1+((iPlan&1)!=0); + } + if( iPlan & 4 ){ + int idx = 1; + if( iPlan & 1 ) idx++; + if( iPlan & 2 ) idx++; + pIdxInfo->aConstraintUsage[iLangTerm].argvIndex = idx; + } + pIdxInfo->idxNum = iPlan; + if( pIdxInfo->nOrderBy==1 + && pIdxInfo->aOrderBy[0].iColumn==1 + && pIdxInfo->aOrderBy[0].desc==0 + ){ + pIdxInfo->orderByConsumed = 1; + } + pIdxInfo->estimatedCost = (double)10000; + + return SQLITE_OK; +} + +/* +** The xUpdate() method. +** +** This implementation disallows DELETE and UPDATE. The only thing +** allowed is INSERT into the "command" column. +*/ +static int amatchUpdate( + sqlite3_vtab *pVTab, + int argc, + sqlite3_value **argv, + sqlite_int64 *pRowid +){ + amatch_vtab *p = (amatch_vtab*)pVTab; + const unsigned char *zCmd; + (void)pRowid; + if( argc==1 ){ + pVTab->zErrMsg = sqlite3_mprintf("DELETE from %s is not allowed", + p->zSelf); + return SQLITE_ERROR; + } + if( sqlite3_value_type(argv[0])!=SQLITE_NULL ){ + pVTab->zErrMsg = sqlite3_mprintf("UPDATE of %s is not allowed", + p->zSelf); + return SQLITE_ERROR; + } + if( sqlite3_value_type(argv[2+AMATCH_COL_WORD])!=SQLITE_NULL + || sqlite3_value_type(argv[2+AMATCH_COL_DISTANCE])!=SQLITE_NULL + || sqlite3_value_type(argv[2+AMATCH_COL_LANGUAGE])!=SQLITE_NULL + ){ + pVTab->zErrMsg = sqlite3_mprintf( + "INSERT INTO %s allowed for column [command] only", p->zSelf); + return SQLITE_ERROR; + } + zCmd = sqlite3_value_text(argv[2+AMATCH_COL_COMMAND]); + if( zCmd==0 ) return SQLITE_OK; + + return SQLITE_OK; +} + +/* +** A virtual table module that implements the "approximate_match". +*/ +static sqlite3_module amatchModule = { + 0, /* iVersion */ + amatchConnect, /* xCreate */ + amatchConnect, /* xConnect */ + amatchBestIndex, /* xBestIndex */ + amatchDisconnect, /* xDisconnect */ + amatchDisconnect, /* xDestroy */ + amatchOpen, /* xOpen - open a cursor */ + amatchClose, /* xClose - close a cursor */ + amatchFilter, /* xFilter - configure scan constraints */ + amatchNext, /* xNext - advance a cursor */ + amatchEof, /* xEof - check for end of scan */ + amatchColumn, /* xColumn - read data */ + amatchRowid, /* xRowid - read data */ + amatchUpdate, /* xUpdate */ + 0, /* xBegin */ + 0, /* xSync */ + 0, /* xCommit */ + 0, /* xRollback */ + 0, /* xFindMethod */ + 0, /* xRename */ + 0, /* xSavepoint */ + 0, /* xRelease */ + 0 /* xRollbackTo */ +}; + +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + +/* +** Register the amatch virtual table +*/ +#ifdef _WIN32 +__declspec(dllexport) +#endif +int sqlite3_amatch_init( + sqlite3 *db, + char **pzErrMsg, + const sqlite3_api_routines *pApi +){ + int rc = SQLITE_OK; + SQLITE_EXTENSION_INIT2(pApi); + (void)pzErrMsg; /* Not used */ +#ifndef SQLITE_OMIT_VIRTUALTABLE + rc = sqlite3_create_module(db, "approximate_match", &amatchModule, 0); +#endif /* SQLITE_OMIT_VIRTUALTABLE */ + return rc; +} |