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Overview
Comment:Extend the json-path mechanism with array indexes of the form "#" or "#-n" for some positive number "n", to reference the end of an array.
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Timelines: family | ancestors | descendants | both | json-path-enhancement
Files: files | file ages | folders
SHA3-256: 35ed68a651f4cf8740597433b0f1c3b345841868022e0904e9f342840ba0e502
User & Date: drh 2019-11-22 17:37:56
Context
2019-11-23
08:51
Enhance the path arguments in JSON functions to access "#-N" array indexes. check-in: ffeec62c user: drh tags: trunk
2019-11-22
17:37
Extend the json-path mechanism with array indexes of the form "#" or "#-n" for some positive number "n", to reference the end of an array. Closed-Leaf check-in: 35ed68a6 user: drh tags: json-path-enhancement
11:49
Fix a harmless compiler warning. check-in: 34343c4b user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to ext/misc/json1.c.

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        pRoot = &pParse->aNode[iRoot];
        pRoot->u.iAppend = iStart - iRoot;
        pRoot->jnFlags |= JNODE_APPEND;
        pParse->aNode[iLabel].jnFlags |= JNODE_RAW;
      }
      return pNode;
    }
  }else if( zPath[0]=='[' && safe_isdigit(zPath[1]) ){
    if( pRoot->eType!=JSON_ARRAY ) return 0;
    i = 0;
    j = 1;
    while( safe_isdigit(zPath[j]) ){
      i = i*10 + zPath[j] - '0';
      j++;
    }


























    if( zPath[j]!=']' ){
      *pzErr = zPath;
      return 0;
    }






    zPath += j + 1;
    j = 1;
    for(;;){
      while( j<=pRoot->n && (i>0 || (pRoot[j].jnFlags & JNODE_REMOVE)!=0) ){
        if( (pRoot[j].jnFlags & JNODE_REMOVE)==0 ) i--;
        j += jsonNodeSize(&pRoot[j]);
      }







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        pRoot = &pParse->aNode[iRoot];
        pRoot->u.iAppend = iStart - iRoot;
        pRoot->jnFlags |= JNODE_APPEND;
        pParse->aNode[iLabel].jnFlags |= JNODE_RAW;
      }
      return pNode;
    }
  }else if( zPath[0]=='[' ){

    i = 0;
    j = 1;
    while( safe_isdigit(zPath[j]) ){
      i = i*10 + zPath[j] - '0';
      j++;
    }
    if( j<2 || zPath[j]!=']' ){
      if( zPath[1]=='#' ){
        JsonNode *pBase = pRoot;
        int iBase = iRoot;
        if( pRoot->eType!=JSON_ARRAY ) return 0;
        for(;;){
          while( j<=pBase->n ){
            if( (pBase[j].jnFlags & JNODE_REMOVE)==0 ) i++;
            j += jsonNodeSize(&pBase[j]);
          }
          if( (pBase->jnFlags & JNODE_APPEND)==0 ) break;
          iBase += pBase->u.iAppend;
          pBase = &pParse->aNode[iBase];
          j = 1;
        }
        j = 2;
        if( zPath[2]=='-' && safe_isdigit(zPath[3]) ){
          unsigned int x = 0;
          j = 3;
          do{
            x = x*10 + zPath[j] - '0';
            j++;
          }while( safe_isdigit(zPath[j]) );
          if( x>i ) return 0;
          i -= x;
        }
        if( zPath[j]!=']' ){
          *pzErr = zPath;
          return 0;
        }
      }else{
        *pzErr = zPath;
        return 0;
      }
    }
    if( pRoot->eType!=JSON_ARRAY ) return 0;
    zPath += j + 1;
    j = 1;
    for(;;){
      while( j<=pRoot->n && (i>0 || (pRoot[j].jnFlags & JNODE_REMOVE)!=0) ){
        if( (pRoot[j].jnFlags & JNODE_REMOVE)==0 ) i--;
        j += jsonNodeSize(&pRoot[j]);
      }

Added test/json105.test.













































































































































































































































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# 2019-11-22
#
# 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 implements tests for "[#]" extension to json-path
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix json104

ifcapable !json1 {
  finish_test
  return
}

# This is the example from pages 2 and 3 of RFC-7396
db eval {
  CREATE TABLE t1(j);
  INSERT INTO t1(j) VALUES('{"a":1,"b":[1,[2,3],4],"c":99}');
}
proc json_extract_test {testnum path result} {
  do_execsql_test json105-1.$testnum "SELECT quote(json_extract(j,$path)) FROM t1" $result
}
json_extract_test 10 {'$.b[#]'}   NULL
json_extract_test 20 {'$.b[#-1]'} 4
json_extract_test 30 {'$.b[#-2]'} {'[2,3]'}
json_extract_test 31 {'$.b[#-02]'} {'[2,3]'}
json_extract_test 40 {'$.b[#-3]'} 1
json_extract_test 50 {'$.b[#-4]'} NULL
json_extract_test 60 {'$.b[#-2][#-1]'} 3
json_extract_test 70 {'$.b[0]','$.b[#-1]'} {'[1,4]'}

json_extract_test 100 {'$.a[#-1]'} NULL
json_extract_test 110 {'$.b[#-000001]'} 4

proc json_remove_test {testnum path result} {
  do_execsql_test json105-2.$testnum "SELECT quote(json_remove(j,$path)) FROM t1" $result
}
json_remove_test 10 {'$.b[#]'}    {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_remove_test 20 {'$.b[#-0]'}  {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_remove_test 30 {'$.b[#-1]'}  {'{"a":1,"b":[1,[2,3]],"c":99}'}
json_remove_test 40 {'$.b[#-2]'}  {'{"a":1,"b":[1,4],"c":99}'}
json_remove_test 50 {'$.b[#-3]'}  {'{"a":1,"b":[[2,3],4],"c":99}'}
json_remove_test 60 {'$.b[#-4]'}  {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_remove_test 70 {'$.b[#-2][#-1]'}  {'{"a":1,"b":[1,[2],4],"c":99}'}

json_remove_test 100 {'$.b[0]','$.b[#-1]'} {'{"a":1,"b":[[2,3]],"c":99}'}
json_remove_test 110 {'$.b[#-1]','$.b[0]'} {'{"a":1,"b":[[2,3]],"c":99}'}
json_remove_test 120 {'$.b[#-1]','$.b[#-2]'} {'{"a":1,"b":[[2,3]],"c":99}'}
json_remove_test 130 {'$.b[#-1]','$.b[#-1]'} {'{"a":1,"b":[1],"c":99}'}
json_remove_test 140 {'$.b[#-2]','$.b[#-1]'} {'{"a":1,"b":[1],"c":99}'}

proc json_insert_test {testnum x result} {
  do_execsql_test json105-3.$testnum "SELECT quote(json_insert(j,$x)) FROM t1" $result
}
json_insert_test 10 {'$.b[#]','AAA'} {'{"a":1,"b":[1,[2,3],4,"AAA"],"c":99}'}
json_insert_test 20 {'$.b[1][#]','AAA'} {'{"a":1,"b":[1,[2,3,"AAA"],4],"c":99}'}
json_insert_test 30 {'$.b[1][#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3,"AAA"],4,"BBB"],"c":99}'}
json_insert_test 40 {'$.b[#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3],4,"AAA","BBB"],"c":99}'}

proc json_set_test {testnum x result} {
  do_execsql_test json105-4.$testnum "SELECT quote(json_set(j,$x)) FROM t1" $result
}
json_set_test 10 {'$.b[#]','AAA'} {'{"a":1,"b":[1,[2,3],4,"AAA"],"c":99}'}
json_set_test 20 {'$.b[1][#]','AAA'} {'{"a":1,"b":[1,[2,3,"AAA"],4],"c":99}'}
json_set_test 30 {'$.b[1][#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3,"AAA"],4,"BBB"],"c":99}'}
json_set_test 40 {'$.b[#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3],4,"AAA","BBB"],"c":99}'}
json_set_test 50 {'$.b[#-1]','AAA'} {'{"a":1,"b":[1,[2,3],"AAA"],"c":99}'}
json_set_test 60 {'$.b[1][#-1]','AAA'} {'{"a":1,"b":[1,[2,"AAA"],4],"c":99}'}
json_set_test 70 {'$.b[1][#-1]','AAA','$.b[#-1]','BBB'} \
     {'{"a":1,"b":[1,[2,"AAA"],"BBB"],"c":99}'}
json_set_test 80 {'$.b[#-1]','AAA','$.b[#-1]','BBB'} \
     {'{"a":1,"b":[1,[2,3],"BBB"],"c":99}'}

proc json_replace_test {testnum x result} {
  do_execsql_test json105-5.$testnum "SELECT quote(json_replace(j,$x)) FROM t1" $result
}
json_replace_test 10 {'$.b[#]','AAA'} {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_replace_test 20 {'$.b[1][#]','AAA'} {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_replace_test 30 {'$.b[1][#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_replace_test 40 {'$.b[#]','AAA','$.b[#]','BBB'} \
     {'{"a":1,"b":[1,[2,3],4],"c":99}'}
json_replace_test 50 {'$.b[#-1]','AAA'} {'{"a":1,"b":[1,[2,3],"AAA"],"c":99}'}
json_replace_test 60 {'$.b[1][#-1]','AAA'} {'{"a":1,"b":[1,[2,"AAA"],4],"c":99}'}
json_replace_test 70 {'$.b[1][#-1]','AAA','$.b[#-1]','BBB'} \
     {'{"a":1,"b":[1,[2,"AAA"],"BBB"],"c":99}'}
json_replace_test 80 {'$.b[#-1]','AAA','$.b[#-1]','BBB'} \
     {'{"a":1,"b":[1,[2,3],"BBB"],"c":99}'}

do_catchsql_test json105-6.10 {
  SELECT json_extract(j, '$.b[#-]') FROM t1;
} {1 {JSON path error near '[#-]'}}
do_catchsql_test json105-6.20 {
  SELECT json_extract(j, '$.b[#9]') FROM t1;
} {1 {JSON path error near '[#9]'}}
do_catchsql_test json105-6.30 {
  SELECT json_extract(j, '$.b[#+2]') FROM t1;
} {1 {JSON path error near '[#+2]'}}
do_catchsql_test json105-6.40 {
  SELECT json_extract(j, '$.b[#-1') FROM t1;
} {1 {JSON path error near '[#-1'}}
do_catchsql_test json105-6.50 {
  SELECT json_extract(j, '$.b[#-1x]') FROM t1;
} {1 {JSON path error near '[#-1x]'}}

finish_test