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Add an optional 5th parameter to the next_char() function that is the

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collating sequence to use for comparison.

FossilOrigin-Name: 9415db6ef255d27ca8473c17e65749a197c30455
This commit is contained in:
drh
2013-07-08 01:27:43 +00:00
parent 3492f4f9af
commit d4b473b2cf
4 changed files with 79 additions and 30 deletions
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75
ext/misc/nextchar.c
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@ -10,12 +10,22 @@
**
******************************************************************************
**
** This file contains code to implement the next_char(A,T,F,W) SQL function.
** This file contains code to implement the next_char(A,T,F,W,C) SQL function.
**
** The next_char(A,T,F,W) function finds all valid "next" characters for
** string A given the vocabulary in T.F. The T.F field should be indexed.
** If the W value exists and is a non-empty string, then it is an SQL
** expression that limits the entries in T.F that will be considered.
** The next_char(A,T,F,W,C) function finds all valid "next" characters for
** string A given the vocabulary in T.F. If the W value exists and is a
** non-empty string, then it is an SQL expression that limits the entries
** in T.F that will be considered. If C exists and is a non-empty string,
** then it is the name of the collating sequence to use for comparison. If
**
** Only the first three arguments are required. If the C parameter is
** omitted or is NULL or is an empty string, then the default collating
** sequence of T.F is used for comparision. If the W parameter is omitted
** or is NULL or is an empty string, then no filtering of the output is
** done.
**
** The T.F column should be indexed using collation C or else this routine
** will be quite slow.
**
** For example, suppose an application has a dictionary like this:
**
@ -184,6 +194,9 @@ static void nextCharFunc(
const unsigned char *zTable = sqlite3_value_text(argv[1]);
const unsigned char *zField = sqlite3_value_text(argv[2]);
const unsigned char *zWhere;
const unsigned char *zCollName;
char *zWhereClause = 0;
char *zColl = 0;
char *zSql;
int rc;
@ -192,25 +205,41 @@ static void nextCharFunc(
c.zPrefix = sqlite3_value_text(argv[0]);
c.nPrefix = sqlite3_value_bytes(argv[0]);
if( zTable==0 || zField==0 || c.zPrefix==0 ) return;
if( argc<4
|| (zWhere = sqlite3_value_text(argv[3]))==0
|| zWhere[0]==0
if( argc>=4
&& (zWhere = sqlite3_value_text(argv[3]))!=0
&& zWhere[0]!=0
){
zSql = sqlite3_mprintf(
"SELECT \"%w\" FROM \"%w\""
" WHERE \"%w\">=(?1 || ?2)"
" AND \"%w\"<=(?1 || char(1114111))" /* 1114111 == 0x10ffff */
" ORDER BY 1 ASC LIMIT 1",
zField, zTable, zField, zField);
zWhereClause = sqlite3_mprintf("AND (%s)", zWhere);
if( zWhereClause==0 ){
sqlite3_result_error_nomem(context);
return;
}
}else{
zSql = sqlite3_mprintf(
"SELECT \"%w\" FROM \"%w\""
" WHERE \"%w\">=(?1 || ?2)"
" AND \"%w\"<=(?1 || char(1114111))" /* 1114111 == 0x10ffff */
" AND (%s)"
" ORDER BY 1 ASC LIMIT 1",
zField, zTable, zField, zField, zWhere);
zWhereClause = "";
}
if( argc>=5
&& (zCollName = sqlite3_value_text(argv[4]))!=0
&& zCollName[0]!=0
){
zColl = sqlite3_mprintf("collate \"%w\"", zCollName);
if( zColl==0 ){
sqlite3_result_error_nomem(context);
if( zWhereClause[0] ) sqlite3_free(zWhereClause);
return;
}
}else{
zColl = "";
}
zSql = sqlite3_mprintf(
"SELECT \"%w\" FROM \"%w\""
" WHERE \"%w\">=(?1 || ?2) %s"
" AND \"%w\"<=(?1 || char(1114111)) %s" /* 1114111 == 0x10ffff */
" %s"
" ORDER BY 1 %s ASC LIMIT 1",
zField, zTable, zField, zColl, zField, zColl, zWhereClause, zColl
);
if( zWhereClause[0] ) sqlite3_free(zWhereClause);
if( zColl[0] ) sqlite3_free(zColl);
if( zSql==0 ){
sqlite3_result_error_nomem(context);
return;
@ -261,5 +290,9 @@ int sqlite3_nextchar_init(
rc = sqlite3_create_function(db, "next_char", 4, SQLITE_UTF8, 0,
nextCharFunc, 0, 0);
}
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "next_char", 5, SQLITE_UTF8, 0,
nextCharFunc, 0, 0);
}
return rc;
}