Cyrus-imapd 3.0.7 xapian searching setup

Hi guys,
I would like to ask for help. I am trying to configure xapian 3.0.7 compiled with enabled xapian support
to actually use xapian indexes.
This is my imapd.conf: 
# Suggested minimal imapd.conf
# See imapd.conf(5) for more information and more options
# Space-separated users who have admin rights for all services.
# NB: THIS MUST BE CONFIGURED
admins: cyrus

## File, socket and DB location settings.
# Configuration directory
configdirectory: /var/lib/imap

# Directories for proc and lock files
proc_path: /run/cyrus/proc
mboxname_lockpath: /run/cyrus/lock

# Locations for DB files
# The following DB are recreated upon initialization, so should live in
# ephemeral storage for best performance.
duplicate_db_path: /run/cyrus/db/deliver.db
ptscache_db_path:  /run/cyrus/db/ptscache.db
statuscache_db_path: /run/cyrus/db/statuscache.db
tls_sessions_db_path: /run/cyrus/db/tls_sessions.db

# Which partition to use for default mailboxes
defaultpartition: default
partition-default: /var/spool/imap

# If sieveusehomedir is false (the default), this directory is searched
# for Sieve scripts.
sievedir: /var/lib/imap/sieve

## Important: KEEP THESE IN SYNC WITH cyrus.conf

lmtpsocket: /run/cyrus/socket/lmtp
idlesocket: /run/cyrus/socket/idle
notifysocket: /run/cyrus/socket/notify

# Syslog prefix. Defaults to cyrus (so logging is done as cyrus/imap
# etc.)
syslog_prefix: cyrus

## Server behaviour settings
# Space-separated list of HTTP modules that will be enabled in
# httpd(8).  This option has no effect on modules that are disabled at
# compile time due to missing dependencies (e.g. libical).
# Fedora default: enable all modules besides admin
httpmodules: caldav carddav domainkey freebusy ischedule rss tzdist webdav

# If enabled, the partitions will also be hashed, in addition to the
# hashing done on configuration directories. This is recommended if one
# partition has a very bushy mailbox tree.
hashimapspool: true

# Disable virtual domains by default
virtdomains: off

## User experience settings
# Minimum time between POP mail fetches in minutes
popminpoll: 1

# Conversation support is required for jmap
conversations: 1
conversations_db: twoskip

# This will default to on in 3.1, and improves compatibility with some Apple
# devices.  Upstream https://github.com/cyrusimap/cyrus-imapd/issues/1556
specialusealways: 1

## User Authentication settings
# Allow plaintext logins by default (SASL PLAIN)
allowplaintext: yes

## SASL library options (these are handled directly by the SASL
## libraries, refer to SASL documentation for an up-to-date list of
## these)
# The mechanism(s) used by the server to verify plaintext passwords.
# Possible values are "saslauthd", "auxprop", "pwcheck" and
# "alwaystrue".  They are tried in order, you can specify more than one,
# separated by spaces.
sasl_pwcheck_method: alwaystrue

# If enabled, the SASL library will automatically create authentication
# secrets when given a plaintext password. Refer to SASL documentation
sasl_auto_transition: no

## SSL/TLS Options
# These three files will automatically be generated by the systemd unit when
# the service starts for the first time.
tls_server_cert: /etc/pki/cyrus-imapd/cyrus-imapd.pem
tls_server_key: /etc/pki/cyrus-imapd/cyrus-imapd-key.pem
tls_client_ca_file: /etc/pki/cyrus-imapd/cyrus-imapd-ca.pem

# File containing the global certificate used for ALL services (imap,
# pop3, lmtp, sieve)
#tls_server_cert: /etc/ssl/certs/ssl-cert-snakeoil.pem

# File containing the private key belonging to the global server
# certificate.
#tls_server_key: /etc/ssl/private/ssl-cert-snakeoil.key


# File containing one or more Certificate Authority (CA) certificates.
#tls_client_ca_file: /etc/ssl/certs/cyrus-imapd-ca.pem

# Path to directory with certificates of CAs.
tls_client_ca_dir: /etc/ssl/certs

# The length of time (in minutes) that a TLS session will be cached for
# later reuse.  The maximum value is 1440 (24 hours), the default.  A
# value of 0 will disable session caching.
tls_session_timeout: 1440
search_engine: xapian
search_index_headers: no
search_batchsize: 8192
defaultsearchtier: t1
t1searchpartition-default: /var/cyrus/search
sync_log_channels: squatter
sync_log: on


Although squatter is creating index and everything looks ok in /var/cyrus/search,
imapd is not accessing any index or database and according to strace monitoring which
i did, it accesses all mail files and not only the one containing my searched string or at least smaller set of files.
I am creating 1 mailbox user/joe and delivering 1000 mails containing short random sets of words.
I triggered search with imtest and commands:
a SELECT "user/joe"
b SEARCH TEXT "monday"

Can anybody please explain to me, in what circumstances is the index supposed to work or what
am i doing wrong?
Thanks for any help or information.
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